The preparation of imidazolidinone and oxazolidinone chelated carbene complexes

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Journal of Organometallic Chemistry 617–618 (2001) 182–208

Mini Review

The preparation of imidazolidinone and oxazolidinone chelated

carbene complexes

Timothy S. Powers ^a, William D. Wulff ^a,*, John Quinn ^a, Yan Shi ^a, Weiqin Jiang ^a,

Richard Hsung ^a, Mark Parisi ^a, Annette Rahm ^a, Xiao Wu Jiang ^a, Glenn P.A. Yap ^b,

Arnold L. Rheingold ^b

^aDepartment of Chemistry, Michigan State Uni6ersity, East Lansing, MI 48824, USA

^bDepartment of Chemistry, Uni6ersity of Delaware, Newark, DE 19716, USA

Received 8 September 2617-618; accepted 4 October 2000

Abstract

The synthesis of several internally chelated imidazolidinone and oxazolidinone Fischer carbene complexes of the type

(CO)₄M=CC(R¹)NCO(CHR²CHR³X) are reported where the M=chromium, tungsten; R¹=methyl, ethyl, iso-propyl, phenyl,

trans-propenyl, iso-propenyl, iso-butenyl, cyclohexenyl and 1-propynyl; R²=H, Ph, Bn, Me, Cy; R³=H, Me, Ph; X=O, NMe.

Four different methods are used for the synthesis of these complexes. The imidazolidinone complexes are best prepared by adding

an imidazolidinone or lithiated imidazolidinone to a methoxy carbene complex or to an in-situ generated acetoxy carbene

complex. a,b-Unsaturated imidazolidinone complexes are prepared by aldol condensations of alkyl imidazolidinone complexes or

by alkylaltion of these complexes with bromomethyl methyl ether and then elimination of methanol. The oxazolidinone complexes

are best made by a two-step procedure that involves the addition of an b-aminoalcohol to a methoxy or acetoxy complex followed

Science B.V.

Keywords: Carbene complexes; Chromium; Tungsten; Imidazaolidinone; Oxazolidinone; Chelated Fischer carbene complexes

have made possible the diversity of the applications in

organic synthesis to which these complexes can now be

1. Introduction

employed. Only a small percentage of various known

The utilization of Fischer carbene complexes in or-

reactions of Fischer carbene complexes have been inves-

ganic synthesis has been actively pursued since their

tigated in their asymmetric versions with a chiral com-

discovery [1] in 1964 and is a ﬁeld that has seen rapid

plex [3]. In principle,

a chiral center could be

growth in recent years [2]. In the thirty three years of

their history, a considerable number of reactions of

Fischer carbene complexes have been discovered that

introduced into a Fischer carbene complex at three

positions. Chiral complexes of the type 1 could be

prepared in which the stabilizing heteroatom X could

be embodied in a chiral alcohol [3,4] or amine [2c,3,5].

A chiral complex could also be generated by replacing

a carbon monoxide ligand with a ligand containing a

chiral center as indicated by the structure 2 [6]. Finally,

a third possibility is to incorporate a chiral center at the

metal center by employing a pseudo-tetrahedral ar-

rangement of ligands as indicated in structure 3 [7]. In

reality, only the reactions of complexes of the type 1

Scheme 1.

* Corresponding author.

PII: S0022-328X(00)00734-8

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

183

cally, the two carbonꢀoxygen single bonds in complex 4

provide two degrees of freedom for rotation of the

chiral center in the alcohol relative to the carbene

carbon. One of these degrees of freedom can be re-

moved if amino complexes of the type 5 are employed

since nitrogen is trivalent and the chiral center can be

embedded in a ring preventing free rotation about the

carbonꢀnitrogen bond to which the chiral center is

appended. One of the drawbacks of complexes of the

type 5 is that a dialkyl amine substituent on carbene

complexes reduces the reactivity to the point where the

complex would loose its generality to many reactions of

interest [9]. It was found that much of this reactivity

can be restored to amino complexes if the nitrogen

atom is destabilized by conjugation to a carbonyl group

[9,10]. An additional advantage of N-acyl carbene com-

plexes is that the carbonyl oxygen usually chelates to

the metal by expulsion of a carbon monoxide ligand

and removes the remaining degree of freedom associ-

ated with rotation about the carbene carbonꢀnitrogen

bond [11]. This would suggest that a complex of the

type 6 would be ideal for asymmetric synthesis since the

chiral center in the pyrrolidine ring would be securely

anchored by the chelation of the carbonyl group. How-

ever, our experience with complexes of this type sug-

gests that complex 6 would not be stable enough to be

handled without special precautions [9]. For these rea-

sons, we initiated a program into the preparation and

evaluation of the imidazolidinone and oxazolidinone

carbene complexes 7 and 8 for use in asymmetric

synthesis [12] (see Scheme 2).

Scheme 2.

Scheme 3.

2. Synthesis of non-chiral imidazolidinone and

oxazolidinone complexes

have been explored to any extent up to this point in

time, however, the results of these studies are just

beginning to come in and it is far too early to be able

to access just what the impact of complexes of this type

will have on the actual asymmetric applications (see

Scheme 1).

The complexes presented in this work have been

prepared by four different procedures three of which

are summarized in Scheme 3. Path A and B are related

in that they both involve the introduction of the intact

imidazolidinone or oxazolidinone 14. For some com-

plexes this can be accomplished by direct replacement

of a methoxyl group in the complex 12 and in others

this approach requires the utilization of the more active

acetoxyl complex 10 which is not readily isolable and

for convenience is generated and reacted in-situ [13].

The third approach outlined in Scheme 3 involves a

two-step procedure that begins with the aminolysis of

the methoxyl complex 12 (or acetoxyl complex 10, not

shown) with either an b-amino ethanol derivative or a

1,2-diaminoethane derivative to give the amino com-

plex 13. The second step requires the formation of the

cyclic urea or cyclic carbamate and then loss of a

carbon monoxide ligand to give the chelated imidazo-

lidinone or oxazolidinone complex 11. The relative

advantage of these three methods will be evaluated for

One of the reasons that complexes of the type 2 have

not been actively pursued is that complexes of this type

(L*-phosphine) are known to undergo relatively facile

cis/trans isomerization which would lead to a loss in

control of asymmetric induction [8]. A limitation asso-

ciated with the development of chiral complexes of the

type 3 is that a resolution would be required after the

complex was synthesized and this has not yet been

achieved despite the fact that some investigations on

complexes of this type have been pursued [7]. While the

majority of investigations of the reactions of chiral

Fischer carbene complexes have been associated with

members of the type 1 complexes, these complexes also

have drawbacks. Complexes of the type 1 derived from

chiral alcohols suffer from the fact that there are likely

to be multiple low energy conformers possible. Speciﬁ-

184

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

consistent with 23 or 24 but these compounds were not

particularly stable and tended to decompose in short

periods when handled in air with no special precau-

tions. The instability of these complexes would appear

not to permit any general applications of their reactions

in asymmetric synthesis. We were thus delighted to ﬁnd

that the imidazolidinone complexes 20 and 21 presented

no special difﬁculties in handling in the presence of air

or water and could be puriﬁed by silica gel chromatog-

raphy in the normal manner. These complexes were

found to be comparable in stability to their correspond-

ing methoxy complex 25 or 26. A solution of the

chromium imidazolidinone complex 20 in ether when

allowed to stand open to the air and room light was

observed to persist for six days compared to seven days

for the methoxy complex 25. Complexes 20 and 21

could be chromatographed on silica gel in air with no

(see Scheme 4) signiﬁcant loss of material. For storage,

these complexes are best kept as crystalline materials in

a vial under nitrogen in the freezer.

the preparation of alkyl, aryl, alkenyl and alkynyl

complexes of the type 11. The fourth method involves

the interconversion of the chelated complexes 11 and in

this work this will be illustrated by alkylation and aldol

addition and elimination reactions.

The chromium and tungsten imidazolidinone com-

plexes 20 and 21 could be prepared in good yields by

the addition of 2-methylimidazolidinone 19 to the ace-

toxyl carbene complexes 17 and 18, respectively. The

methoxyl complexes 25 and 26 were unreactive to the

imidazolidinone 19. A reaction was observed upon

addition of the N-lithio derivative of 19 but no signiﬁ-

cant amount of either 20 or 21 was formed in this

reaction. The oxazolidinone complexes 23 or 24 could

not be prepared in signiﬁcant amounts by the addition

of oxazolidinone 22 to the acetoxyl complexes 17 and

18. These reactions lead to the formation of a complex

mixture of products, which were not carefully charac-

terized. In some instances a small amount of a com-

pound could be obtained whose spectral data were

All attempts to prepare the oxazolidinone complexes

23 and 24 by the two-step procedure outlined in

Scheme 3 were unsuccessful. Similar observations have

been made before and disclosed in a report which

revealed that attempted closure of amino complexes of

the type 13 (X=O) leads to a process in which the

metal is lost and which leads to the ultimate formation

of ene carbamates [14]. The example from this work

shown in Scheme 5 illustrates the formation of the ene

carbamate 30. The oxazolidinone carbene complex 28

could not be isolated from reactions which generated

the oxazolidinone ring either from triphosgene or

diphenyl carbonate as phosgene equivalents. In the case

of the latter reagent, it was surmised that the desired

trans-propenyl oxazolidinone carbene complex 28 un-

derwent Michael addition of phenoxide ion and then

protonation of the enolate 29 at the metal center and

reductive elimination lead to the observed product 30,

which was interestingly formed as a single diastereomer.

We have observed that b-amino ethanol will add to the

methoxyl complex 25 in near quantitative yield but we

were not able to close the oxazolidinone ring in the

second step (i.e. 13 to 11 in Scheme 3). This closure was

attempted with several reagents including phosgene

(vide infra) but, the instability of the product suspected

of being 23 for the reasons discussed above, dissuaded

us from an extensive search for conditions to generate

the methyl oxazolidinone complexes by Path C.

Scheme 4.

As summarized by the information in Scheme 6 it is

possible to prepare and isolate the oxazolidinone car-

bene complexes 37 and 38 which bear a trans-propenyl

group on the carbene ligand by the two step procedure

involving aminolysis and then closure of the oxazolidi-

none ring. The aminolysis with b-aminoethanol is car-

ried out on the chromium and tungsten methoxyl

complexes 33 and 34 and in each case a very high yield

Scheme 5.

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

185

Finally, it can be mentioned that extensive investigation

revealed that Path C is far superior to Path A for the

preparation of the oxazolidinone complexes 37 and 38.

The only success encountered with experiments on Path

A involved the addition of the n-lithio derivative of 14

to the reactive intermediate generated by treatment of 9

with triﬂic anhydride and resulted in 38 only in low

yields (5–10%) which were not reproducible.

Confronted with the fact the Z-isomer can be closed

and the E-isomer cannot, a method for the isomeriza-

tion of these complexes was needed if efﬁcient overall

yields of the oxazolidinone complexes 37 and 38 were

to be realized. Since the dianion of complex 35 (or 36)

is ﬁrst generated in the successful closure with phos-

gene, it appears that the nitrogen anion in these com-

plexes cannot undergo inversion. This was conﬁrmed in

experiments in which the E-isomer of the tungsten

complex 36 was treated with either one or two equiva-

lents of butyllithium and then quenched with water to

provide a quantitative recovery of 36 in which no trace

of the Z-isomer could be detected. Interestingly, the

hydroxyl proton in the E-isomer of 36 is the most acidic

proton in the molecule and does not exchange with the

amino proton, since upon treatment with one equiva-

lent of butyllithium and then D₂O the hydroxyl proton

at l=2.17 is absent but the amino proton at l=8.65

was still present. The thermal barrier to the interconver-

sion of the tungsten complex 36 is quite high since

heating the E-isomer of this complex in THF at 70°C

for 24 h lead to a 90% recovery and no detectable

formation of the Z-isomer. The high barrier to rotation

of an amino carbene complex is due to the signiﬁcant

amount of double-bond characters for the NꢀCcarb

bond due to the donation of the nitrogen lone pair of

electrons into the empty pz orbital of the carbene

carbon [16]. One method to overcome this is suggested

by an observation made by Fischer that a tertiary

amine such as DABCO can form the 1:1 adduct 41 with

the chromium carbene complex 40 [17]. This idea was

well placed since treatment of a 1:1 mixture of E- and

Z-isomers of the tungsten complex 36 with one equiva-

lent of 4-dimethylaminopyridine (DMAP) in THF at

70°C for 24 h lead to a mixture enriched to 80% of the

Z-isomer (85% recovery). The yellow solution of com-

plex 36 becomes deep red when DMAP is added and

remains this color until the aqueous workup. A ¹³C-

NMR spectrum of this solution did not provide any

evidence for a tetrahedral intermediate and thus if

involved is likely in an unfavorable equilibrium.

Nonetheless, treatment with DMAP does provide a

method for isomerization of amino complexes 35 and

36 to the isomer required for closure to the oxazolidi-

none complexes and as such represents the ﬁrst amine

induced isomerization of an amino carbene complex

(see Scheme 7).

Scheme 6.

Scheme 7.

of the amino complex is obtained as a 1:1 mixture of

rotamers. The two rotamers are easily separable by

silica gel chromatography and the stereochemistry is

assigned by ¹H-NMR according to the method by

Fischer [15] and by X-ray analysis (vide infra). Many

failed attempts were registered in an effort to close the

oxazolidinone ring. Neither the E or Z-isomer of 35 or

36 would undergo closure upon reaction with either

dimethylcarbonate, methyl chloroformate, carbonyldi-

imidazole or triphosgene in the presence of base. Suc-

cess was achieved when the Z-isomer was treated with

two equivalents of butyllithium and then 1.5 equiva-

lents of phosgene. The chromium and tungsten com-

plexes 37 and 38 were both obtained in good yields as

deep purple solids that once obtained in the solid form

could be stored at −30°C for several days. However,

both complexes are sensitive to water and thus an

aqueous workup was avoided but silica gel chromatog-

raphy in air at ambient temperatures was tolerated. It

was rather interesting to ﬁnd that while the Z-isomer

could be closed with phosgene, the E-isomer was totally

resistant to the same procedure. Instead, the chlorofor-

mate complex 39 was isolated from the reaction with

the E-isomer in 65% yield. This compound could not be

coaxed to close to the oxazolidinone complex 38 either

by heating at 70°C for 24 h or by treating with either

one or two equivalents of butyllithium at −78°C.

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T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

The synthetic route developed for the synthesis of the

45 cannot be separated by silica gel chromatography

and thus the crude reaction mixture was taken on to the

oxazolidinone 46 in 18% overall yield from 40. The 18%

overall yield of phenyl complex 46 suggests that only

the Z-isomer will undergo ring closure to form an

oxazolidinone ring as is the case for the trans-propenyl

complex 38. To conﬁrm this pure or enriched samples

of the E- and Z-isomers of 45 would be required. While

no separation at all could be achieved by silica gel

chromatography, the major E-isomer of 45 could be

crystallized from the mixture to give a 35% yield of

pure compound. The best purity for the Z-isomer that

was obtained in a mother liquor was an enrichment of

78:22. A sample of this enriched Z-isomer was treated

to the ring closing conditions with phosgene to give a

60% yield of the oxazolidinone complex 46 and as

expected, when the pure E-isomer was treated to the

same conditions, no detectable amount of complex 46

was observed. A limitation in the synthesis of the

phenyl oxazolidinone complex 46 from 40 by Path C is

that the overall efﬁciency of the conversion could not

be improved by isomerization of the E-isomer into the

Z-isomer. Heating the E-isomer complex 45 with

DMAP under the conditions that were successful for

complex 38 lead to signiﬁcant decomposition with loss

of the carbene ligand to give a DMAP complex of

chromium pentacarbonyl. The small amount of mate-

rial that was recovered was still predominately the

E-isomer (ꢀ2:1). The synthesis of 46 may be better

effected by Path B as it is for complex 51 (Scheme 9)

but this has not yet been investigated. As was shown in

the case of the E-isomer of complex 36, the E-isomer of

45 could not be isomerized to the Z-isomer with butyl-

lithium. Treatment of 45-E with 2 equivalents of n-

butyllithium at −78°C for 30 min and then quenching

with water gave a 92% recovery of the carbene complex

trans-propenyl oxazolidinone complexes 37 and 38

shown in Scheme 6 can be extended to the synthesis of

the phenyl and iso-butenyl complexes 46 and 44, re-

spectively. Aminolysis of the iso-butenyl methoxyl com-

plex 42 with b-aminoethanol gives an 80% yield of a

mixture of stereoisomers in which the E-isomer is pre-

dominant in an 88:12 ratio. The major E-isomer could

be obtained in pure form by silica gel chromatography

but the minor Z-isomer could only be obtained in pure

form with repeated elutions. Treatment of the E-isomer

of 43 with two equivalents of n-butyllithium and then

phosgene lead to the oxazolidinone 44 which is in

contrast to the trans-propenyl complex 36 for which

only the Z-isomer could be closed. The aminolysis of

the phenyl complex 40 with b-aminoethanol also gave

predominantly the E-isomer of the expected amino

carbene complex. The combined yield of the E- and

Z-isomers of 45 vary between 90–100%. The isomers of

1

which was determined by H-NMR to be exclusively

the E-isomer. In a similar fashion, a sample of 45 with

a 1.4:1 E:Z ratio was unchanged when treated in the

same way (see Scheme 8).

Scheme 8.

The assignment of the major isomer of 35 as either

the E- or Z-isomer was not a straightforward analysis.

The stereochemistry of amino carbene complexes can

reliably be assigned by the relative chemical shifts of

protons on the nitrogen substituents [15]. The protons

on the Z-isomer are closer to the metal center and as a

result are always shifted downﬁeld relative to those of

the E-isomer. This relationship also holds for the pro-

ton on nitrogen in secondary amino complexes as can

be seen for complexes 43 and 45 (Table 1). This is not

true for complex 35 in which the most downﬁeld shifts

for both the NH proton and the methylene protons are

found in the same isomer (Z). Adding to the confusion

are the observations that the Z-isomer, but not the

E-isomer, of complexes 35 and 45 can be converted to

the oxazolidinone complex. This is to be compared to

Scheme 9.

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

187

Table 1

E and Z-isomers of b-aminoethanol carbene complexes

Complex

Isomer

NꢀH chemical shift

N(CH2)20 chemical shift

Close to oxazolidinone

35

43

45

E-isomer

Z-isomer

E-isomer

Z-isomer

E-isomer

Z-isomer

8.90

8.98

9.21

8.88

9.49

9.00

3.64–3.97

4.01–4.14

3.60–3.85

4.06–4.17

overlap

no

yes

no

yes

overlap

the observation that the E-isomer of 43 can be con-

verted to the oxazolidinone complex 44. These dis-

crepancies were resolved by solving the solid state

structure of the E-isomers of chromium complexes 35,

43 (as its acetate derivative) and 45. As a result it was

found that the use of the chemical shift of the NH

proton was unreliable in the assignment of the stereo-

chemistry of 35, whereas, the chemical shift of the

methylene protons would allow for the correct predic-

tion of the stereochemistry of 35. The reason for the

fact that the Z-isomers of 35 and 45 can be closed to

oxazolidinone complexes and the E-isomers cannot is

not understood at this time. Also not understood, is the

reason that the E-isomer of 43 will undergo closure to

an oxazolidinone while the E-isomers of 35 and 45 will

not. The ring closing reactions with phosgene require

the dianion of the complex be generated with two

equivalents of n-butyllithium and it is possible that the

dianion of 43 can isomerize while those of 35 and 45

can not. To test for this, a sample of 43 with an E:Z

ratio of 6.0:1 was treated with two equivalents of

butyllithium in THF at −78°C for 30 min followed by

a water quench to give an 87% recovery of complex 43

with an E:Z ratio that was unchanged. As described

above, the same observations were made for 35 and 45.

Thus the origin of this difference can not be identiﬁed

as this time.

The alkynyl oxazolidinone complex 50 is prepared in

a manner similar to complexes 35, 43 and 45 except in

this case the aminolysis must be carried out at −100°C

to minimize the formation of the Michael adduct which

is known to be a serious side reaction in the aminolysis

of alkynyl complexes [18]. Even at −100°C, the reac-

tion of the alkynyl complex 47 with aminoethanol gives

substantial amounts of Michael adduct 48 along with

the desired amino complex 49 which is obtained as one

isomer that is tentatively assigned as the Z-isomer. At

higher temperatures, small amounts of the E-isomer can

be observed. Treatment of 49-Z with two equivalents of

butyllithium and then phosgene gives the alkynyl oxa-

zolidinone complex 50 in 42% yield. The phenyl imida-

zolidinone complex 51 was most easily prepared by

Path C (Scheme 3) involving the addition of the lithi-

ated imidazolidinone 19 to the methoxy carbene com-

plex 40 to give the desired product directly in 85%

yield. Complex 51 was a robust orange solid that in the

crystalline form is stable in air at room temperature

(r.t.) for extended periods without decomposition.

In contrast to the a,b-unsaturated oxazolidinone

complexes 37 and 38, the corresponding imidazolidi-

none complexes could only be efﬁciently obtained by an

aldol condensation [12b] of the methyl imidazolidinone

complexes 20 and 21 (Scheme 10). Attempts to prepare

complex 52 by the addition of the lithiated imidazolidi-

none 19 to the methxoy complex 33 via path B in

Scheme 3 or the protonated imidazolidinone 19 to

in-situ generated acetoxy or triﬂoxy complexes accord-

ing to path A in Scheme 3 did not result in the

formation of signiﬁcant amounts of complex 52. The

aldol addition adducts were isolated but not puriﬁed

prior to elimination with triethylamine with the excep-

tion of the tungsten styryl complex 55 which underwent

elimination during the isolation of the aldol adduct.

The trans-propenyl complexes 52 and 53 were isolated

as reddish–purple solids and the styryl complexes were

obtained as deep Prussian blue solids. The imidazolidi-

none complexes are more stable than the oxazolidinone

complexes. When a sample of 52 was dissolved in ether

and shaken with water and then the bilayer allowed to

stand exposed to room light and at r.t. the color of the

complex did not visibly fade until after 2 days whereas

a sample of complex 37b began to fade after 2 h when

treated in the same manner.

The imidazolidinone complexes can be alkylated in

good yields with methyl triﬂate and bromomethyl

methyl ether as illustrated in Scheme 11. Treatment of

Scheme 10.

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T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

Scheme 11.

in-situ from the ammonium salts 67 and 68 gave the

ethyl complex 56 and 58 in 7 and 10% yields,

respectively.

complex 20 with butyllithium and then methyl triﬂate

gave an 81% yield of the ethyl complex 56 and an 8%

yield of the iso-propyl complex 57 along with a 9% of

the starting material. The ethyl complex 56 could not

be separated from 20 or 57 but subsequent alkylation of

the mixture with additional methyl triﬂate gave the

iso-propyl complex 57 in 95% yield which was one

compound. The same alkylation of the tungsten methyl

complex 21 was more selective giving only trace

amounts of the over alkylated product 59 and only

trace amounts of starting material unreacted. The tung-

sten complex 58 could be further alkylated with bro-

momethyl methyl ether to give the complex 62 in 80%

yield with no over alkylation. The corresponding

chromium complex 60 could be prepared by the se-

quential double alkylation of 20 with methyl triﬂate

and then with bromomethyl methyl ether to give com-

plex 60 in 62% yield which could be separated from the

over-alkylated products 61 and 57. The elimination of

methanol could be achieved from complexes 60 and 62

to give the iso-propenyl complexes 64 and 65 in high

yields. In a similar fashion, methanol could be elimi-

nated from the puriﬁed complex 61 to give the 1-

methoxyl-2-propenyl complex 66 in 85% yield. The

ethyl complexes 56 and 58 could not be prepared by the

direct method indicated in Scheme 4 that was successful

for the methyl complexes 20 and 21. Reaction of the

imidazolidinone 19 with acetoxy complexes generated

3. Synthesis of chiral imidazolidinone and oxazolidinone

complexes

The chiral methyl substituted imidazolidinone com-

plexes 72–75 were prepared by Method A in the same

manner as the non-chiral methyl complexes 20 and 21

(Scheme 4). All of the complexes are derived from (4R,

5S)-1,5-dimethyl-4-phenyl-2-imidazolidinone 70 which

was prepared by the fusion of urea with (-)-ephedrine

hydrochloride 69 by the method of Close [19]. The use

of the imidazolidinone auxiliary 70 has the attractive

feature that both enantiomers of ephedrine 69 are

commercially available and therefore both enantiomers

of 70 can be easily prepared by the Close method. The

corresponding cyclohexyl substituted imidazolidinone

71 can be prepared by hydrogenation of the phenyl ring

with hydrogen in the presence of rhodium chloride

according to the method of Drewes, Malissa and Roos

[19c]. Hydrogenolysis of the benzylic carbonꢀnitrogen

bond was not observed. Complexes derived from both

imidazolidinones 70 and 71 were prepared by Method

A according to the procedure developed for the non-

chiral complexes 20 and 21 (Scheme 4). As indicated in

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

189

Scheme 12.

Scheme 12, the yields of the methyl carbene complexes

were lower for both the chromium and tungsten series

with the cyclohexyl auxiliary 71, however, the yields for

the phenyl substituted auxiliaries 72 and 73 were essen-

tially the same as for the non-chiral analogs 20 and 21.

The unknown imidazolidinone 79 was prepared from

the diamine 78 which in turn was prepared from the

commercially available (R)-phenylglycine chloride hy-

drochloride 77 as indicated in Scheme 13. The imidazo-

lidinone 79 can be prepared in excellent yields from the

diamine 78 by reaction with phosgene in the presence of

aqueous potassium hydroxide. It was interesting to ﬁnd

that imidazolidinone 79 could also be prepared from

the diamine 78 by fusion with urea utilizing the same

procedure that was developed by Close for the prepara-

tion of the imidazolidinone 70 from the amino alcohol

69 [19]. The attachment of the imidazolidinone auxil-

iary 79 to a chromium carbene complex proceeded

smoothly to give complex 80 following the method

developed for complex 72.

enriched in the Z-isomer. With the exception of com-

plex 95, the rotamers of both the tungsten and

chromium complexes could be easily separated by chro-

matography and multigram quantities of the Z-ro-

tamers were obtained as stable, yellow crystalline solids.

The oxazolidinone complexes 91–95 were prepared in

good yields from the Z-rotamers and phosgene with the

procedure developed for the non-chiral complexes 37

and 38. These complexes were obtained as deep purple

solids, which in crystalline form, could be stored under

argon in a freezer for several weeks without signiﬁcant

decomposition. However, these complexes are most

conveniently used immediately after preparation.

The procedure for the preparation of the chiral oxa-

zolidinone carbene complexes 91–95 was slightly

modiﬁed from that used for the preparation of the

non-chiral complexes 37 and 38 (Scheme 6). Due to the

increased steric bulk of the chiral amines, the aminoly-

sis of the trans-propenyl methoxy complex 33 was

sluggish and the yields of the corresponding amino

complexes were low. This problem was circumvented by

adding the chiral amines to the acetoxy complex gener-

ated in-situ from the ammonium salts 81 and 82 (Table

2). The yields of the aminolysis reaction were good but

unfortunately mixtures of rotamers were obtained with

the major rotamer as the undesired E-rotamer. As was

found to be the case with the non-chiral amino com-

plexes 35 and 36, only the Z-rotamers of 86–90 could

be cyclized to the oxazolidinone complex with phos-

gene. The stereochemistry of the rotamers of complexes

The preparation of cyclohexenyl substituted imidazo-

lidinone carbene complexes was not possible by either

method A or B in Scheme 3 and the synthesis of the

corresponding oxazolidinone complexes proved difﬁcult

and was achieved via method C as outlined in Scheme

1

86–90 was assigned by H-NMR correlation with com-

plexes 35, 43 and 45 whose structures were determined

by X-ray diffraction (Table 1). Isomerization of the

E-rotamers was effected using DMAP as described

earlier affording decent overall yields of complexes

Scheme 13.

190

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

Table 2

Preparation of trans-propenyl oxazolidinone complexes

M

R¹

R²

R³

Amino alcohol

Aminolysis complex

Aminolris

% Yield

Isomerization

Chelated complex ^a

Z

% Yield

E:Z

Me

Ph

H

Bn

Ph

H

83

84

85

86

87

88

89

90

74

70

73

71

78

88:12

80:20

88:12

90:10

88:12

87

85

87

85

20:80

20: 80

25: 75

33:67

20:80

91

92

93

94

70%

68%

95 ^b45%

^aUnless otherwise speciﬁed, yields are given from puriﬁed Z-isomer.

^bForm a 20:80 mixture of E:Z isomers. Yield based on the amount of Z-isomer.

Scheme 14.

of DMAP was isolated from this reaction. Substitution

of diazabicyclooctane (DABCO) for DMAP gave a

62% yield with a 3.5:1 ratio. The best results were

obtained with 4-pyrrolidinopyridine which gave a 68%

recovery with an E:Z ratio of 2.3:1. Treatment of this

mixture to the cyclization conditions developed for the

synthesis of complex 37 gave desired oxazolidinone

complex 100 in 63% yield based on the Z-isomer of 98.

The chiral a,b-unsaturated imidazolidinone com-

plexes 101 and 102 were prepared by an aldol conden-

sation with the procedure that was developed for the

preparation of the non-chiral analogs 52 and 53

(Scheme 10). The methyl imidazolidinone complexes

have been shown to give high asymmetric induction for

the formation of the aldol adducts 103 for a variety of

aldehydes [3,12a] and also in adducts from the Michael

reaction [12c]. They have been shown to be effective

chiral synthons for acetate enolates in the aldol reaction

since the aldol adduct carbene complexes can be con-

verted to the b-hydroxy acids 104 in high yields. The

elimination of the aldol adduct carbene complexes 103

to the aldol condensation carbene complexes of the

type 101 is much more facile than for simple alkoxy

carbene complexes [20] or simple dialkylamino com-

14. The preparation of cyclohexenyl imidazolidinone

complexes via method C has not yet been explored. The

amino alcohol complexes 98 were prepared by aminoly-

sis of the methoxyl complex 97 in yields that were much

higher than by aminolysis of an in-situ generated ace-

toxy complex which was the opposite of the observa-

tions made for the trans-propenyl complexes 86 (Table

2). The aminolysis of the methoxy complex 97 with

(R)-phenylglycidol proceeded in high yields, but to the

detriment of the synthesis of complex 100, the reaction

was highly selective for the formation of the E-isomer.

As was the case for complex 35 and 45, treatment of the

E-isomer of 98 with butyllithium and then phosgene

gave only a chloroformate and none of the desired

oxazolidinone complex. Enhanced amounts of the Z-

isomer could not be obtained by performing the

aminolysis of 97 at r.t. (79% yield, E:Z 19:1) or in

methylene chloride at r.t. either in the presence or

absence of triethylamine (50–60% yield, E:Z]80:1).

Isomerization of the 98-E to the Z-isomer with 4-

dimethylamino pyridine (DMAP) with the procedure

developed for the complexes 35 and 36 gave 44%

recovery of the complex with an E:Z ratio of 3.1:1 after

48 h. A 37% yield of pentacarbonyl chromium complex

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

191

plexes [21]. For both of these classes of complexes,

elimination of the b-hydroxy requires activation as a

mesylate, whereas, the imidazolidinone complex 103

can be induced to dehydrate by simple exposure to

triethylamine. The reason for this may be related to the

acidity of the imidazolidinone complexes. The acidity of

these complexes has not been determined but is antici-

pated to be intermediate between alkoxy [22] and

amino complexes [23] and closer to that of water and

alcohols. The a,b-unsaturated complexes have been

shown to give high asymmetric inductions in exo-selec-

tive Diels–Alder reactions [12d]. Finally the chiral

phenyl imidazolidinone complex 106 can be prepared in

good yield by the addition of the lithiated imidazolidi-

none 105 to the methoxy complex 40. Complex 106 has

been shown useful in the asymmetric synthesis of

silanes and stannanes [12e](see Scheme 15).

This leads to greater reactivity for the oxazolidinone

complexes for certain reactions such as the Diels–Alder

reaction. However, in this case the higher stability of

the imidazolidinone complex wins out since the reac-

tions can be performed at higher temperatures where

higher overall efﬁciencies can be achieved. The imidazo-

lidinone complexes can be stored cold in a vial sealed

with a rubber septa which has been ﬂushed with nitro-

gen for prolonged periods without substantial decom-

position. The oxazolidinone complexes are best used

directly after their preparation but good yields can still

be obtained in a number of applications. Further stud-

ies on the synthetic applications of both classes of

complexes in a number of different reactions of Fischer

carbene complexes will be reported.

4. Experimental

Although not all of the permutations have yet been

investigated, the present investigation reveals that the

aryl and methyl substituted imidazolidinone complexes

are best prepared by the direct introduction of an

imidazolidinone unit according to path A or B in

Scheme 3 and oxazolidinone complexes are best made

by the two step procedure involving aminolysis and the

ring closure as indicated by path C in Scheme 3.

Unsaturated imidazolidinone complexes can be ac-

cessed by aldol condensation reactions of alkyl substi-

tuted complexes. From the point of view of synthetic

utilization, imidazolidinone complexes would appear to

be the most attractive since they are far more stable

than the oxazolidinone complexes. This difference is

manifested in the fact that the methyl substituted oxa-

zolidinone complexes 23 and 24 are too unstable to be

isolated. This instability is presumably related to the

decreased electron density on nitrogen in the oxazolidi-

none complexes vs. the imidazolidinone complexes.

All reagents were obtained from commercial suppli-

ers and used without further puriﬁcation unless other-

wise indicated. Tetrahydrofuran, ether and benzene

were distilled from benzophenone ketyl under nitrogen.

Dichloromethane and hexane were distilled from cal-

cium hydride. High-resolution mass spectra were

recorded on a VG 70-250 instrument or obtained from

the Midwest center for Mass Spectrometry in Lincoln,

NE. Elemental analyses were done by Galbraith Labo-

ratories in Knoxville, TN. Optical rotations were ob-

tained on

a

Perkin–Elmer 141 polarimeter at

wavelength of 589 nm (sodium D line) using 1.0 deci-

meter cells. Speciﬁc rotations, [h]^Dare reported in

degrees per decimeter at 25°C and the concentration (c)

is given in grams per 100 ml.

4.1. Preparation of 1-methyl-2-imidazolidinone (19)

[24]

A solution of 2-imidazolidinone (15.2 g, 177 mmol)

in 200 ml of 1,4-dioxane was prepared in a 500 ml

3-neck ﬂask equipped with a condenser. Sodium hy-

dride (60 wt% in parafﬁn, 8.33 g, 208 mmol) was added

slowly under an atmosphere of nitrogen with vigorous

stirring. The milky solution was heated to 65°C and

stirred at this temperature for 2 h and then cooled to

0°C. Methyl iodide (20.4 ml, 328 mmol) was added

slowly via syringe and the resulting mixture was stirred

at r.t. for 14 h. The reaction mixture was ﬁltered

through a bed of Celite and the solvent removed in a

rotary evaporator. Flash chromatography (10% MeOH

in CH₂Cl₂, R_f=0.15) on a 2×15’’ plug of silica gel in

a large column (two portions) gave 9.2 g of the title

compound as a white solid in 52% yield. Further crys-

tallization from CHCl₃–hexane gave 19 as white crys-

tals. Spectral data for 19: m.p. 112–113°C (lit

1

Scheme 15.

114–115°C) [24]; H-NMR (500 MHz, CDCl₃) l 2.75

192

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

(s, 3H), 3.39 (s, 4H), 5.20 (br s, 1H). ¹³C-NMR (75

MHz, CDCl₃) l 30.25, 37.68, 47.17, 163.40; IR (neat)

3268 s, 2866 m, 1699 vs, 1503 m, 1452 m, 1404 m, 1280

m, 1257 m cm⁻¹; mass spectrum, m/z (relative inten-

sity) 100 M⁺(100), 85 (5), 78 (7), 71 (23), 65 (3); Anal.

Calc. for C₄H₈N₂O: C, 47.97; H, 8.06; N, 27.99. Found:

C, 47.68; H, 8.14; N, 28.28%.

began to form, and was collected via ﬁltration and

washed with cold hexane (3×5 ml). The solid was

identiﬁed as the chelated complex 20 which was ob-

tained in 99% yield (323.0 mg). Complex 20a: yellow

1

solid, R_f=0.40 (CH₂Cl₂); H-NMR (CDCl₃) l 2.97 (s,

3H), 3.48 (s, 3H), 3.60 (t, 2H, J=7.3 Hz), 4.64 (t, 2H,

J=7.3 Hz). Complex 20b: yellow solid, R_f=0.40

(CH₂Cl₂); ¹H-NMR (CDCl₃) l 3.00 (s, 3H), 3.09 (s,

3H), 3.54 (t, 2H, J=7.2 Hz), 4.06 (t, 2H, J=7.2 Hz).

4.2. Preparation of [methyl-[3-(1-methyl-2-

imidazolidinone)]methylene] tetracarbonylchromium (0)

(20)

4.3. Preparation of [methyl-[3-(1-methyl-2-

imidazolidone)]methylene] tetracarbonyltungsten (0) (21)

Tetramethylammonium (1-hydroxy-ethylidene) pen-

tacarbonylchromium (0) [25] 15 (500 mg, 1.62 mmol)

was dissolved in 6 ml of CH₂Cl₂and cooled to −78°C

under an atmosphere of argon. Freshly distilled acetyl

bromide (110 ml, 1.49 mmol) was added dropwise and

the deep reddish-purple solution was stirred for 1 h

after which time a solution of 1-methyl-2-imidazolidi-

none 19 (149 mg, 1.49 mmol) in 3 ml of CH₂Cl₂was

added dropwise via cannula. The solution was gradu-

ally warmed to −60°C over a 30 min period and

stirred at this temperature for 12 h. The mixture was

quickly warmed to r.t. and concentrated on a rotary

evaporator to remove half of the solvent. The remain-

ing dark reddish–brown solution was loaded onto a

silica gel column and the product eluted with CH₂Cl₂

(R_f=0.39) to give 221 mg of title compound as a dark

red solid in 51% yield. Other runs have given up to 70%

yield. Shorter reactions times (−45°C 1 h, −20°C 1 h)

also can give yields of ꢀ50%. Spectral data for 20:

Complex 21 was prepared according to the procedure

described for 20. Crystallization from CH₂Cl₂and hex-

ane afforded 0.29 g of 21 as ruby-red prisms in 62%

1

yield. Spectral data for 21: m.p. 128°C (dec.); H-NMR

(500 MHz, CD₂Cl₂) l 2.73 (s, 3H), 3.10 (s, 3H), 3.93 (t,

2H, J=8.3 Hz), 4.03 (t, 2H, J=8.3 Hz); ¹³C-NMR (75

MHz, acetone-d₆, −50°C) l 30.97, 34.87, 42.36, 49.43,

165.53, 207.06, 216.66, 221.14, 292.51; IR (neat) 2005

(s), 1864 (vs), 1818 (s), 1382 (m), 1300 (m) cm⁻¹; mass

spectrum, FAB (3-NBA), m/z (relative intensity) 422

M⁺(10, ¹⁸²W), 394 (8), 366 (5), 307 (15), 219 (5), 154

(100); Calc. for C₁₀H₁₀N₂O¹₅⁸²W, FAB (3-NBA), m/z

420.0073, measured 420.0082.

4.4. Preparation of [trans-propenyl-(2-hydroxy-

ethylamino)methylene] pentacarbonylchromium (0)

(35-E) and (35-Z)

1

m.p. 134°C (dec.); H-NMR (500 MHz, CD₂Cl₂) l 3.00

(s, 3H), 3.03 (s, 3H), 3.93 (t, 2H, J=6.9 Hz), 3.95 (t,

2H, J=6.5 Hz); ¹³C-NMR (500 MHz, acetone-d₆, −

50°C) l 30.49, 33.34, 42.24, 49.34, 162.54, 216.44,

231.87, 232.07, 312.52; ¹³C-NMR (300 MHz, CD₂Cl₂) l

31.11, 33.86, 41.43, 48.99, 162.32, 216.10, 231.83,

232.15, 317.33; IR (neat) 1999 m, 1917 vs, 1884 vs, 1830

vs, 1716 m, 1384 m cm⁻¹; mass spectrum, m/z (relative

intensity) 290 M⁺(6), 273 (2), 262 (5), 206 (10), 178 (2),

154 (100); Anal. Calc. for C₁₀H₁₀N₂O₅Cr, FAB (3-

NBA), m/z 289.9994, measured 290.0003. Anal. Calc.

for C₁₀H₁₀N₂O₅Cr: C, 41.39; H, 3.47; N, 9.65. Found:

C, 41.47; H, 3.35; N, 9.64%.

In some reactions, a mixture of two compounds (20a

and 20b) was isolated which comprised the front run-

ning yellow band (R_f=0.40) just ahead of the deep red

band containing 20 (R_f=0.39). The mixture would turn

red upon standing at r.t. in air. These compounds are

tentatively identiﬁed as the two atropisomers of the

pentacarbonyl analogs of 20 since it was found that

they could be converted to 20. A mixture of 20a and

20b (358.0 mg, 1.13 mmol) was dissolved in 5 ml of

CH₂Cl₂and heated to reﬂux for 5 min. Then 5 ml of

hexane was added and the mixture was heated to reﬂux

again for 5–10 min. Upon cooling, a red precipitate

Trans-propenyl (methoxy) pentacarbonyl chromium

(0) 33 [27] (1.53 g, 5.54 mmol) was dissolved in 12 ml of

THF and cooled to −90°C under an atmosphere of

argon. Ethanolamine (0.37 g, 6.10 mmol) was dissolved

in 6 ml of THF and added to the solution dropwise.

After the addition was complete, the yellow solution

was immediately warmed to r.t. and concentrated on a

rotary evaporator. The resulting oil was chro-

matographed on silica gel with CH₂Cl₂–Et₂O (2:1) to

give 0.77 g of trans-propenyl (2-aminoethanol) pen-

tacarbonyl chromium (0) 35-E (46%, R_f=0.58) and

0.78 g of the 35-Z (47%, R_f=0.51) as yellow solids in

93% combined yield. The stereochemistry was assigned

1

by H-NMR [15] and by X-ray diffraction of the E-iso-

mer (vide infra). Complex E-rotamer was isomerized as

described in the general procedure to give a 80:20 ratio

of Z to E respectively, in 85% combined yield after

chromatography. The OH signals for both the E and Z

1

rotamers were not located by H-NMR. Spectral data

for 35-E: m.p. 100–102°C; ¹H-NMR (500 MHz,

CDCl₃) l 1.97 (d, 3H, J=6.8 Hz), 3.64–3.67 (m, 2H),

3.90–3.97 (m, 2H), 6.21 (dq, 1H, J=15.0, 6.5 Hz), 6.61

(d, 1H, J=15.6, Hz), 8.90 (br s, 1H, NH); ¹³C-NMR

(75 MHz, CDCl₃) l 19.23, 50.34, 60.53, 136.80, 139.22,

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

193

218.10, 223.17, 272.92; IR (neat) 3305 (m), 2049 (s),

1906 (shoulder, vs), 1886 (vs), 1529 (m), 1069 (m)

4.6. General procedure for the isomerization of amino

carbene complexes with 4-dimethylamino-pyridine

1

cm⁻¹. Spectral data for 35-Z: m.p. 68–70°C; H-NMR

The appropriate amino carbene complex (1.00 eq)

was dissolved in THF to make a 0.20 M solution and

4-dimethylaminopyridine (1.00 eq) was added and the

mixture was stirred until all the reactants had dissolved.

The reaction ﬂask was then degassed by the freeze-thaw

method, backﬁlled with an atmosphere of argon at r.t.

The stopcock was closed and the ﬂask placed in a

pre-heated oil bath set at 70°C. The yellow solution was

stirred for approximately 24 h upon which the mixture

became deep red. After cooling to r.t., the reaction ﬂask

was opened and diluted with ether. The mixture was

washed with 1 N HCl (3×), saturated aqueous NH₄Cl

(1×), and NaCl (1×). The yellow solution was dried

over MgSO₄, ﬁltered, and concentrated on a rotary

evaporator. The crude products were chomatographed

with the appropriate solvent system to afford enrich-

ments of the desired Z-rotamers as described in the

individual preparation with \85% recovery of the

mass balance in each case. Control experiments have

shown that isomerization of the E-rotamers does not

occur thermally in the absence of 4-dimethylaminopy-

ridine. However, it remains to be determined whether

isomerization occurs with the same efﬁciency using

catalytic amounts of DMAP.

(500 MHz, CDCl₃) l 1.85 (d, 3H, J=6.8 Hz), 4.01–

4.03 (m, 2H), 4.11–4.14 (m, 2H), 5.63 (dq, 1H, J=

15.0, 6.5 Hz) 6.88 (d, 1H, J=15.6), 8.98 (br s, 1H,

NH); ¹³C-NMR (75 MHz, CDCl₃) l 17.70, 54.07,

61.08, 124.11, 145.96, 217.83, 223.70, 267.34; IR (neat)

3305 (m), 3287 (w), 2054 (s), 1910 (vs), 1538 (m), 1045

(m) cm⁻¹; mass spectrum (mixture of rotamers), m/z

(relative intensity) 305 M⁺(20), 277 (35), 193 (55), 165

(100), 135 (40), 119 (45), 110 (65); Anal. Calc. for

C₁₁H₁₁O₆CrN (mixture of rotamers): C, 43.25; H, 3.63;

N, 4.59. Found C, 43.93; H, 3.95; N, 4.55.

4.5. Preparation of [trans-propenyl(2-hydroxy-

ethylamino)methylene] pentacarbonyltungsten (0) (36-E)

and (36-Z)

Complex 36 was prepared from complex 34 [27] (1.95

g, 4.68 mmol) with the procedure described above for

complex 34. Puriﬁcation gave 0.92 g of complex 36-E

(R_f=0.32) in 47% yield and 0.93 g of complex 36-Z

(R_f=0.26) in 48% yield as yellow solids. Spectral data

for 36-E: m.p. 115–117°C; ¹H-NMR (500 MHz,

CDCl₃) l 2.02 (d, 3H, J=6.3 Hz), 2.17 (s, 1H, OH),

3.60 (q, 2H, J=5.3 Hz), 3.88–3.93 (m, 2H), 6.52 (d,

1H, J=15.2 Hz), 6.61 (dq, 1H, J=15.0, 6.5 Hz), 8.65

(br s, 1H, NH); ¹³C-NMR (75 MHz, CDCl₃) l 19.36,

50.06, 60.29, 137.24, 147.02, 199.11, 202.93, 251.37; IR

4.7. General procedure for the preparation of

oxazolidinone carbene complexes

The Z-rotamer of the appropriate amino carbene

complex (1.00 eq) was dissolved in THF (0.15 M) and

cooled to −78°C under an atmosphere of argon and

n-butyllithium (2.05 eq, 1.6 M in hexanes) was added

dropwise. After stirring for 5 min, a solution of phos-

gene (1.50 eq, 1.93 M in toluene) was added and the

dark red solution was warmed to r.t. over a 30 min

period. The dark solution was stirred at r.t. until the

solution became deep purple. The mixture was concen-

trated after ꢀ1.5 h on a rotary evaporator and the

purple residue was quickly(!) chomatographed on silica

gel with the appropriate solvent system affording the

desired complex. The isolated chelated complex was

dissolved in a small amount of CH₂Cl₂and was slowly

crashed out of solution by the dropwise addition of

pentane. The deep-red micro-crystalline solids obtained

though this procedure are stable at −30°C under

argon for weeks with only slight decomposition. How-

ever, these complexes are best used immediately follow-

ing their preparation.

(neat) 3300 (m), 2056 (s), 1885 (vs), 1527 (m) cm⁻¹

.

1

Spectral data for 36-Z: m.p. 65–67°C; H-NMR (500

MHz, CDCl₃) l 1.90 (d, 3H, J=6.3 Hz), 3.99–4.01 (m,

4H), 5.94 (dq, 1H, J=15.0, 6.5 Hz) 6.75 (d, 1H,

J=15.2), 8.82 (br s, 1H, NH) (OH signal not located);

¹³C-NMR (75 MHz, CDCl₃) l 17.37, 56.12, 60.80,

130.46, 146.70, 198.26, 203.52, 247.30; IR (neat) 3291

(m), 2062 (s), 1900 (vs), 1540 (m), 1443 (m), 1402 (m),

1049 (m), 958 (m) cm⁻¹; mass spectrum (mixture of

rotamers), m/z (relative intensity) 437 M⁺(50, ¹⁸⁴W),

409 (30), 381 (30), 353 (85), 295 (85), 267 (100), 240

(65); Calc. for C₁₁H₁₁NO¹₆⁸⁴W (mixture of rotamers)

m/z 437.0097, measured 437.0074.

A 86:14 ratio of complexes 36-E and 36-Z, respec-

tively, were isomerized as described in the general pro-

cedure to give a 80:20 ratio of 36-Z to 36-E,

respectively, in 85% combined yield after chromatogra-

phy. Attempted isomerization of 36-E with both one

and two equivalents of n-butyllithium in THF at −

78°C followed by D₂O quench gave exclusive recovery

1

of the E-iomser in 85% yield. The H-NMR data for

4.8. Preparation of [trans-propenyl(2-oxazo-

36-E obtained from treatment with one equivalent of

butyllithium had the OH signal (l 2.17) absent and the

spectrum of 36-E from the experiment with two equiva-

lents had both the OH the NH signals (l 8.65) absent.

lidinone)methylene] tetracarbonylchromium (0) (37)

Complex 37 was prepared as described in the general

procedure starting with 0.27 g (0.89 mmol) of 35-Z to

194

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

give, after chromatography using CH₂Cl₂–hexane (3:1,

R_f=0.35), 0.22 g of 37 in 70% yield as a deep reddish–

purple solid. Spectral data for 37: m.p. 95°C (dec.);

¹H-NMR (500 MHz, CD₂Cl₂) l 2.17 (d, 3H, J=6.8

Hz), 4.40 (t, 2H, J=7.6 Hz), 5.08 (t, 2H, J=7.5 Hz),

7.07 (d, 1H, J=14.5 Hz), 7.84 (dq, 1H, J=14.4, 7.6

Hz); ¹³C-NMR (75 MHz, acetone-d₆, −50°C) l 21.56,

45.59, 72.75, 138.99, 160.98, 165.48, 217.13, 232.62,

233.17, 302.37; IR (neat) 2007 (vs), 1866(vs), 1816 (vs),

1702 (s), 1615 (s), 1420 (s), 1260 (s), 1226 (s) cm⁻¹; mass

spectrum, FAB (3-NBA), m/z (relative intensity) 303

M⁺(50), 275 (40), 247 (80), 219 (60), 174 (35), 154

(100), 136 (90), 89 (55); Calc. for C₁₁H₉NO₆Cr, FAB

(3-NBA), m/z 302.9835, measured 302.9848.

solution of tetramethyl ammonium bromide (5.18 g,

0.051 mol) in 10 ml water was added. The water layer

was extracted with three 40 ml portions of methylene

chloride. The combined organic layers are dried with

MgSO₄and ﬁltered through a plug of Celite. The ﬁltrate

was treated with methyl triﬂate (6 g, 0.036 mol). After

30 min, the solvent was removed and the dark red oil

was loaded onto a silica gel column and eluted with

hexanes. Fractions containing complex 42 were concen-

trated and cooled to −78°C. The product crystallized

from solution and was collected by fast cold ﬁltration

and then dried under vacuum to give 6.8 g (70%) of

carbene complex 42 as dark red crystals. Spectral data

1

for 42: m.p. 33ꢀ34°C, R_f=0.28 (Hexane); H-NMR

(CDCl₃) l 1.88 (s, 3H), 1.91 (s, 3H), 4.72 (s, 3H), 7.26

(s, 1H); ¹³C-NMR CDCl₃l 21.99, 27.62, 66.18, 140.12,

141.50, 216.72, 223.96, 338.90; IR (neat): 2058 s, 1930

brs, 1590 m, 1451 m, 1251 m, 1186 m, 976 m; mass

spectrurm, m/z (relative intensity) 290 M⁺(23), 262 (6),

234 (7), 206 (11), 178 (27), 150(100), 135 (10), 120 (23),

107 (16), 91 (13), 82 (17), 75 (5), 67 (5); HRMS calc. for

C₁₁H₁₀O₆Cr: 289.9882, found 289.9876.

4.9. Preparation of [trans-propenyl(2-oxazo-

lidinone)methylene] tetracarbonyltungsten (0) (38)

Complex 38 was prepared as described in the general

procedure starting with 1.13 g (2.58 mmol) of 36-Z to

give 0.65 g of 92 in 58% yield as a deep reddish–purple

solid after chromatography using EtOAc–hexane (1:1,

R_f=0.50). Smaller scale reactions starting with 0.50 g

(1.14 mmol) of 36-Z led to the isolation of 38 in 70%

yield. Spectral data for 38: m.p. 141–143°C (dec.);

¹H-NMR (500 MHz, CD₂Cl₂) l 1.92 (d, 3H, J=7.0

Hz), 4.12 (t, 2H, J=8.0 Hz), 5.07 (t, 2H, J=8.4 Hz),

6.51 (d, 1H, J=14.5 Hz), 8.18 (dq, 1H, J=14.4, 7.1

Hz); ¹³C-NMR (75 MHz, acetone-d₆, −50°C) l 21.52,

45.55, 72.31, 139.84, 164.52, 169.66, 207.14, 217.35,

220.34, 278.82; IR (neat) 2007 (vs), 1866 (vs), 1816 (vs),

1702 (s), 1615 (s), 1420 (s), 1260 (s), 1226 (s) cm⁻¹; mass

spectrum: no parent ion observed, 351 M⁺(10,

¹⁸⁴W(CO)₆); Calc. for C₁₁H₉NO¹₆⁸²W, FAB (3-NBA),

m/z 432.9913, measured 432.9902.

4.11. Preparation of of

[iso-butenyl(2-hydroxyethylamino)methylene]

pentacarbonylchromium (0) (43)

Methoxy isobutenyl carbene complex 42 (3.5 g, 0.012

mol) was put in ﬂask with 200 ml dry THF. This was

cooled to −78°C for 15 min. Ethanol amine (0.74g,

0.012 mol) was added as a 20 ml THF solution. TLC

showed immediate product formation (CH₂Cl₂, R_f=

0.3). The solution turned from bright red to light yellow

after 10 min. This was stirred at −78°C for 1 h and at

r.t. for 30 min. Then the reaction mixture was concen-

trated and run through a short column (1:1 hex-

ane:CH₂Cl₂ꢀCH₂Cl₂). The crude-NMR showed E:Z

7:1. The major product was isolated as yellow crystals

and identiﬁed as the E-isomer (1.89 g, 49%). The stere-

The chloroformate complex 39 was isolated in 65%

yield as a yellow oil when the procedure described above

was used starting with 36-E instead of 36-Z. Spectral

data for 39: ¹H-NMR (500 MHz, CDCl₃) l 2.05 (d, 3H,

J=7.3 Hz), 3.82 (q, 2H, J=5.7 Hz), 4.52 (t, 2H, J=5.3

Hz), 6.49 (d, 1H, J=14.7 Hz), 6.67 (dq, 1H, J=15.0,

6.7 Hz), 8.50 (br s, 1H); IR (neat) 3300 (w), 2062 (vs),

1

ochemistry of the major product was assigned by H-

NMR [15] and conﬁrmed by X-ray diffraction of the

acetate derivative 107 (vide infra). The Z-isomer was

obtained as a viscous oil mixed with E-isomer. Spectral

data for 43-E: m.p. 53ꢀ55°C, R_f=0.29, (CH₂Cl₂);

¹H-NMR (CDCl₃) l 1.52 (s, 3H), 1.83 (s, 3H), 3.60 (s,

2H), 3.85 (s, 2H), 6.18 (s, 1H), 9.21 (s, 1H); ¹³C-NMR

(CDCl₃) l 19.52, 24.51, 51.29, 60.59, 124.02, 133.29,

217.61, 223.49, 279.34; IR (neat) 3357m, 2053 s, 1929

brs, 654 s; mass spectrum, m/z (relative intensity) 319

M⁺(100), 291 (42), 285 (7), 263 (18), 235 (43), 231 (7),

219 (23); HRMS m/z calc. for C₁₂H₁₃O₆NCr 319.0148,

found 319.0162. Anal. Calc. for C₁₂H₁₃O₆NCr: C, 45.15;

H, 4.10; N, 4.39. Found: C, 44.95; H, 4.23; N, 3.92%.

1903 (m), 1816 (vs), 1773 (m), 1512 (w), 1158 (m) cm⁻¹

.

4.10. Preparation o [iso-butenyl(methoxy)methylene]

pentacarbonylchromium (0) (42)

To a solution of 1-bromo-2-methyl propene (5.00 g,

0.037 mol) in 100 ml of THF at −78°C was added

t-butyl Lithium (0.074 mol, 43.6 ml of 1.7 M solution in

pentanes). After 1.5 h this solution was transferred via

cannula to a slurry of chromium hexacarbonyl complex

(7.4 g, 0.034 mol) in 200 ml THF at r.t. The resulting

yellow solution was stirred for 1.5 h and then stripped

of solvent to leave a dark red viscous oil. This oil was

dissolved in a minimum amount of water and then a

1

Spectral data for 43-Z: R_f=0.33, (CH₂Cl₂), H-NMR

(CDCl₃) l 1.62 (s, 3H), 1.69 (s, 3H), 4.06 (s, 2H), 4.17

(s, 2H), 6.53 (s, 1H), 8.88 (s, 1H).

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

195

4.11.1. Equilibration of 43-E, Z 6ia its lithium anion

A solution of n–butyllithium (2.5 M solution in

hexanes, 0.44 mmol) was added to a solution of 43 (70

mg, 0.22 mmol, E:Z 6.0:1) in 3 ml of THF cooled to

−78°C. The yellow reaction solution was stirred for 30

min and quenched with water. The aqueous solution was

extracted with ether, dried over anhydrous MgSO₄, and

concentrated to yield 61 mg (87%) of 43 with an E:Z

ratio of 6.0:1. The above reaction was repeated with 43

(70 mg, 0.22 mmol, E:Z 6.0:1) and was warmed to r.t.

for 30 min before quench. The carbene complex was

recovered in 77% yield (54 mg) with an E:Z ratio of

3.8:1.

product) are stirred at r.t. for 2 h after which time TLC

showed a purple spot (R_f=0.55, CH₂Cl₂) grew at the

expense of the yellow spot. At this point, IR shows

chelate complex formation was complete. After puriﬁca-

tion on a short silica gel column (CH₂Cl₂) dark purple

crystals of 44 were obtained (0.5g, 50%). The highest

yield of a series of runs is 78%. The product is somewhat

sensitive to air and stored under argon. Spectral data for

44: m.p. 160ꢀ162°C (dec.), R_f=0.55 (CH₂Cl₂), ¹H-

NMR (CDCl₃) l 2.07 (s, 3H), 2.30 (1s, 3H), 4.03 (t, 2H,

J=8.1 Hz), 4.93 (t, 2H, J=8.1 Hz), 6.51(s, 1H);

¹³C-NMR (some decomposition occurs during aquisi-

ition) (CD₂Cl₂) l 22.21, 28.25, 44.93, 71.45, 134.53,

152.82, 216. 98, 312.31; IR (neat): 2054 m, 2013 s, 1904

s, 1840 s, 1714 m, 1413 m, 1254 m, 1191 m, 1204 m; mass

spectrum, m/z (relative intensity) 317 M⁺(5), 289 (3),

233 (6), 220 (7), 205 (32), 165 (12), 153 (13), 108 (20), 94

(24), 80 (37), 67 (17), 52 (100); HRMS calc. for

C₁₂H₁₁O₆NCr 316.9991, found 316.9983.

4.11.2. Acetylation of 43 to gi6e its acetate deri6ati6e

(107)

The amino carbene complex 43-E (0.070 g, 0.220

mmol), Ac₂O (0.021 g, 0.241 mmol) and Et₃N (0.0206 g,

0.034 mmol) were dissolved in 5 ml THF. This solution

was stirred at r.t. for 5 h until TLC showed the

disappearance of starting material (R_f=0.20, CH₂Cl₂).

The solution was concentrated and loaded onto a small

silica gel column. After ﬂushing with 50% ether in pet

ether, the yellow band was collected. The volatiles were

removed to leave a bright yellow solid (70 mg, 90%)

which was crystallized from ether–pentane at −20°C.

The structure of this compound was determined by

4.13. Synthesis of of [phenyl(2-hydroxy-

ethylamino)methylene] pentacarbonylchromium (0) (45)

A solution of ethanolamine (210 ml, 3.48 mmol) in 1.5

ml of THF was added dropwise to a solution of phenyl-

methoxy chromium carbene complex 40 [28] (1.122 g,

3.59 mmol) in 10 ml THF cooled to −78°C. Upon

completion of the addition the solution changed color

from dark red to yellow. The solution was warmed to r.t.

and ﬁltered through a 1:1 mixture of Celite and silica gel.

The yellow solution was concentrated to yield a thick

yellow gum which began to crystallize on standing. The

amino carbene complex exists as a mixture of rotamers

(E:Z 5.8:1 by ¹H-NMR integration of the amine protons

at l 9.49 & 9.0) about the carbene carbonꢀnitrogen

bond. The isomers are inseparable by silica gel chro-

matography, however, the E isomer may be obtained in

35% yield via crystallization of the crude product from

benzene–hexane. The stereochemistry of the major

1

X-ray diffraction. Spectral data for 207: H-NMR 500

MHz CDCl₃l 1.49 (s, 3H), 2.12 (s, 3H), 3.69 (m, 2H),

4.27 (m, 2H), 6.17 (s, 1H), 9.06 (brs, 1H); ¹³C-NMR 300

MHz CDCl₃l 19.54, 20.61, 24.59, 48.85, 61.67, 124.21,

133.07, 171.00, 217.43, 223.26, 382.51; IR (neat) 1942w,

1900m, 1878s, 661m; mass spectrum m/z (relative inten-

sity) 361 M⁺(12), 333 (8), 305 (2), 277 (6), 249 (8), 221

(51), 191 (45), 178 (12), 169 (86), 149 (12), 133 (9), 125

(6), 111 (28), 96 (100), 82 (75), 67 (46), 52 (43); HRMS

m/z calc. for C₁₄H₁₅O₇Cr 361.0254, found 361.0242.

Greenish yellow plates (Et₂O–Pentane, −20°C); m.p.

48ꢀ50°C; R_f=0.54, CH₂Cl₂.

1

product was assigned by H-NMR [15] and by X-ray

4.12. Prearation of [iso-butenyl(2-oxazo-

lidinone)methylene] tetracarbonylchromium (0) (44)

diffraction (vide infra). Spectral data for 45-E: Yellow

needles (benzene–hexanes), m.p. 81–83°C; R_f=0.58

1

(1:1 hexane:EtOAc); H-NMR (CDCl₃) l 1.77 (br s, 1

A 250 ml ﬂask was charged with 100 ml THF and

carbene complex 43-E (1.01 g, 3.176 mmol). The bright

yellow solution was cooled to −78°C and n-BuLi (2.60

ml of 2.5 M in hexanes, 6.51 mmol) was added slowly.

The yellow solution was stirred at −78°C for 30 min

and then phosgene (1.65 ml of 1.93 M in Toluene, 3.176

mmol) was added dropwise. The solution turned dark

brown and TLC showed a dark yellow spot (R_f=0.58,

CH₂Cl₂). The reaction mixture was warmed to r.t. for 1

h. The volatiles were removed and the residue was

passed through a plug of silaca gel. The fractions

containing the dark yellow product (non-chelate

H), 3.36 (q, 2 H, J=5.4 Hz), 3.79 (br s, 2H), 6.81 (d,

2 H, J=7.1 Hz), 7.22 (t, 1 H, J=7.5 Hz), 7.40 (t, 2 H,

J=7.87 Hz), 9.49 (br s, 1H); ¹³C-NMR (CDCl₃) l 51.7,

60.8, 119.0, 126.751, 128.6, 149.6, 217.1, 223.4, 283.0; IR

(NaCl, neat) 3598 m, 3222 br w, 2056 m), 1985 m, 1947

br s, 1897* br s, 1547 m, 1439 w, 1097 w, 703w, 680 m,

665 m cm⁻¹; mass spectrum m/z (relative intensity) 341

(M⁺, 6), 313 (7), 285 (5), 257 (8), 229 (17), 201 (40), 171

(23), 147 (68), 117 (100), 103 (25), 91 (80), 77 (50), 52

(42). Anal. Calc. for C₁₄H₁₁NO₆Cr: C, 49.27; H, 3.25; N,

4.10. Found: C, 49.48; H, 3.25; N, 4.07%. Spectral data

196

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

1

for 45-Z: In the H-NMR (CDCl₃) the amine proton

appears at l 9.0 (0.5 ppm upﬁeld from the amine

proton in the E isomer). Integration of these two peaks

has been the basis for assigning isomer ratios. All of the

4.13.3. Attempted equilibration of 45-E,Z 6ia its

lithium anion

A solution of n-butyllithium (0.10 ml of a 2.5M

solution in hexane, 0.25 mmol) was added to a solution

of 45 (34 mg, 0.10 mmol, E:Z 1.40:1) in 1 ml of THF

cooled to −78°C. The yellow reaction solution was

stirred for 30 min and quenched with water. The

aqueous solution was extracted with ether, dried over

anhydrous MgSO₅, and concentrated to yield 32 mg

(94%) of 45 with an E:Z ratio of 1.36:1. The above

reaction was repeated with pure 45-E (102 mg, 0.30

mmol, E:Z\40:1). The carbene complex was recovered

in 92% yield with no interconversion of rotamers as

1

other H-NMR resonances overlap with the E isomer.

4.13.1. Attempted puriﬁcation of 45-Z 6ia its Acetate

Acetic anhydride (0.39 ml, 4.1 mmol) was added to a

solution of a mixture of 45-Z and 45-E (1.286 g, 3.8

mmol, E:Z 5.2:1) and TEA (0.58 ml, 4.2 mmol) in 10 ml

of THF. The reaction was stirred for 2 h at r.t. and

quenched with saturated NaHCO₃solution. The

aqueous solution was extracted with ether, dried over

anhydrous MgSO₄, and concentrated to yield 1.30 g

(90%) of the acetate amino carbene complex as a yellow

oil. The two isomeric acetates were partially separable

with silica gel chromatography using 90:10 (hexane–

EtOAc). Sodium methoxide (\5 mg, catalytic) was

added to a solution of the acetate (60 mg, 0.157 mmol,

E:Z 3.9:1) in 1 ml of methanol. The reaction was stirred

for 5 min at r.t. and poured into pH 7.0 phosphate

buffer. The aqueous solution was extracted with ether

and dried over anhydrous MgSO₄. Solvent removal

yielded 42 mg (79%) of 45 with an E:Z ratio of 3.4:1.

The reaction was repeated with 130 mg of the acetate

(0.339 mmol, E:Z 1.4:1) in 2 ml of methanol. This gave

a 77% recovery of 45 with an E:Z ratio of 1.34:1.

1

indicated by H-NMR. When the reaction was repeated

with pure 45-E and the solution allowed to warm to r.t.

for 30 min before aqueous quench, the complex 45 was

recovered in 84% yield as a 14:1 mixture of E:Z

isomers.

4.14. Synthesis of of [phenyl(2-oxazolidinone)methylene]

tetracarbonylchromium (0) (46)

The chelate carbene complex is best obtained by

reaction of the crude aminolysis product without fur-

ther puriﬁcation. The crude yellow gum from the above

reaction (complex 45) was dissolved in 10 ml THF,

cooled to −78°C, and treated dropwise with butyl-

lithium (2.9 ml of a 2.5 M solution in hexane, 7.25

mmol). This solution was stirred for 30 min and then

cannulated into a solution of phosgene (1.9 ml of a 1.93

M solution in toluene dissolved in 30 ml of THF, 3.67

mmol) at r.t. and stirred for 90 min. The reaction was

concentrated and puriﬁed via silica gel chromatography

using 70:30 hexane:ethyl acetate as the eluting solvent.

The dark red gum thus obtained was crystallized from

CH₂Cl₂–hexane to yield 239 mg (20%) of the title

compound as lustrous bronze colored needles. Spectral

data for 46: Bronze crystals (CH₂Cl₂–hexane), m.p.

4.13.2. Isomerization of 45 with DMAP

A single-neck ﬂask equipped with a threaded teﬂon

high vacuum stopcock was charged with amino carbene

complex 45 (506 mg, 1.48 mmol, E:Z 6.8:1) and DMAP

(181 mg, 1.48 mmol) in 8 ml of THF. The ﬂask was

sealed, freeze-pump-thawed (3 cycles), back-ﬁlled with

argon at r.t. and placed on a 75°C oil bath. The

reaction turned bright orange. The reaction was stirred

for 24 h, cooled, and concentrated to an orange gum.

Silica gel chromatography returned 436 mg (86%) of

the starting carbene complex along with 34 mg (7%) of

the DMAP:Cr(CO)₅decomposition product. The ﬁnal

1

130°C (dec.); R_f=0.47 (1:1 hexane:EtOAc); H-NMR

(CD₂Cl₂) l 4.07 (br s, 2 H), 4.93 (br s, 2 H), 7.45–7.20

(m, 5 H); ¹³C-NMR (CD₂Cl₂) l 45.0, 71.5, 123.6, 128.8,

130.3, 147.0, 163.6, 216.2, 317.6; IR (NaCl, neat) 2015

s, 1901 s, 1840 s, 1710 w, 1257 w, 1220 m, 702 w, 663

w cm⁻¹; mass spectrum m/z (relative intensity), (M⁺

not found) 191 (23), 105 (100), 77 (38), 51 (14).

1

E:Z ratio was 6.0:1 by H-NMR integration. This reac-

tion was repeated with 61 mg of 45 with a starting E:Z

ratio of 1.40:1. After 24 h the ﬁnal ratio was 2.3:1,

however the recovery was very low (ꢀ10%). This

reaction was repeated again with pure 45-E (90 mg,

0.235 mmol) in 1.1 ml of THF with 35 mg DMAP

(0.286 mmol). After the reaction had stirred for 40 h,

4.15. Preparation of the of

[1-propynyl(2-hydroxyethylamino)methylene]

pentacarbonylchromium (0) (49-Z)

1

an aliquot was withdrawn for H-NMR analysis. This

showed the rotamer ratio to be 2.2:1. The heating was

continued until the total time was 132 h (5.5 days). At

this point the carbene complex was recovered (12 mg,

13%) with an E:Z ratio of 1.46:1. This recovered com-

plex was re-subjected to the isomerization conditions

for another 204 h (8.5 days). No carbene complex was

recovered from this reaction.

Carbene complex 47 (548 mg., 2 mmol) was dissolved

in 24 ml of diethyl ether and cooled to −100°C. To

this solution was added dropwise a solution of 1-etha-

nol-2-amine (0.121 ml, 122.2 mg, 2 mmol) in 6.5 ml of

diethyl ether. TLC showed that the reaction began

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

197

4.17. Synthesis of [phenyl-[3-(1-methyl-2-imidazolidi-

none)]methylene] tetracarbonylchromium (0) (51)

immediately after addition but did not proceed to com-

pletion. The formation of a white solid, presumably

1-ethanol-2-amine, was observed. The reaction mixture

was allowed to warm up gradually over 30 min. When

the mixture was placed in a −10°C bath, the reaction

went to completion in 30 min. After concentration, the

two major product were puriﬁed from the crude reac-

tion mixture by chromatography on silica gel with a 2:1

mixture of hexane and ethyl acetate as eluent to give

the Michael adduct 48 (213.1 mg, 0.636 mmol) as a

yellow solid in 32% yield and the alkynyl amino com-

plex 49 (335.1 mg, 1.171 mmol) as a yellow solid in 59%

yield. The stereochemistry of 49 was tentatively as-

signed as Z on the basis that it would close to give 50.

Depending on the reaction temperature, small amounts

of the E-isomer of 49 can be formed in this reaction.

Spectral data for 49-Z: m.p. 100–101°C; ¹H-NMR

(CDCl₃) l 2.40 (s, 3 H), 3.86–3.88 (m, 4 H), 9.10 (bs, 1

H); ¹³C-NMR (CDCl₃) l 6.2, 53.8, 60.9, 82.3, 131.6,

217.2, 223.4, 259.2; IR (ﬁlm) 3595w, 3272w, 2055m,

1915s, 1894s, 1539m; mass spectrum (EI) m/z (relative

intensity) 303 M⁺(22), 275 (16), 232 (2), 219 (11), 191

(34), 178 (3), 163 (100), 149 (6), 133 (32), 121 (11), 108

(35), 91 (19), 80 (22), 71 (23), 66 (8), 52 (88), 45 (8);

Anal. calc. for C₁₁H₉NO₆Cr: C, 43.58; H, 2.99; N, 4.62.

Found: C, 43.74; H, 2.70; N, 4.55%. Spectral data for

A solution of butyllithium (2.2 ml of a 2.5 M solu-

tion in hexane, 5.5 mmol) was added dropwise over

several min to a stirred solution of 1-methyl-2-imidazo-

lidinone 19 (547 mg, 5.46 mmol) in 30 ml of THF

cooled to −78°C. The reaction was stirred for 5 min at

−78°C and then allowed to warm to r.t. The anion

solution was then again cooled to −78°C and a solu-

tion of phenyl-methoxy chromium carbene complex 40

[28] (1.705 g, 5.46 mmol) in 15 ml THF was added via

cannula. The transfer was completed upon rinsing with

two 5 ml portions of THF. The reaction was stirred 5

min at −78°C. The reaction was then allowed to warm

to r.t. and stirred for an additional 60 min. The reac-

tion was concentrated and puriﬁed via silica gel chro-

matography using 1:1 hexane:ethyl acetate as the

eluting solvent. The dark red gum thus obtained was

crystallized in two crops from CH₂Cl₂–hexane to yield

1.637 g (85%) of lustrous black needles. Spectral data

for 51: Dark purple–black crystals (CH₂Cl₂–hexane),

m.p. 137–140°C (dec.); R_f=0.22 (1:1 hexane:EtOAc);

¹H-NMR (CD₂Cl₂) l 3.01 (s, 3 H), 3.85 (m, 4 H,

J=4.1 Hz), 7.32 (d, 1 H, J=7.6 Hz), 7.39 (d, 1 H,

J=7.3 Hz), 7.42 (d, 1 H, J=7.4 Hz), 7.51 (m, 2 H);

¹³C-NMR (CD₂Cl₂) l 31.3, 42.9, 49.2, 123.0, 128.7,

129.6, 146.4, 163.1, 216.4, 231.1, 233.8, 312.3; IR

(NaCl, neat) 2005 s, 1887 br s, 1831 s, 1717 s, 1370 m,

1

48: H-NMR (CDCl₃) l 2.04 (s, 3 H), 3.46 (bs, 2 H),

3.84 (bs, 2 H), 4.41 (s, 3 H), 6.18 (s, 1 H), 9.31 (s, 1 H).

1300 m, 1262 w, 1226 w, 704 w, 673 w, 628 w cm⁻¹

;

mass spectrum m/z (relative intensity, M⁺not found)

4.16. Preparation of of [propynyl(2-oxazolidinone)-

methylene] tetracarbonylchromium (0) (50)

220 (65), 108 (92), 80 (100), 52 (100).

The amino complex 49-Z (150.0 mg, 0.50 mmol) was

dissolved 3 ml of THF [0.15 M] at −78°C, and 411.0

ml of n-BuLi [2.47 M in hexane] (1.01 mmol, 2.05 eq)

was added dropwise. After 45 min, the dianion solution

was transferred dropwise via a cannula to 385.0 ml of a

phosgene solution [1.93 M in toluene] (0.743 mmol, 1.5

eq) that was diluted with 40 ml of CH₂Cl₂. The mixture

was stirred at −78°C for 20 min and then at r.t. for 15

min. After evaporation of the solvent under reduced

pressure (not to dryness), the residue was chro-

matographed on a silica gel column (size: 1.5×30 cm,

gradient eluent: 0–100% CH₂Cl₂in hexane) to provide

62.7 mg of 50 (42%) as a purple red solid. R_f=0.65

4.18. Preparation of [trans-propenyl-[3-(1-methyl-

2-imidazolidinone)]methylene] tetracarbonyl-chromium

(0) (52)

A solution of complex 20 (149 mg, 0.52 mmol) in 5

ml THF was cooled to −78°C under an atmosphere of

argon. A 1.6 M solution of n-BuLi (0.34 ml, 0.54

mmol) in hexanes was then added dropwise and the

resulting yellow solution was stirred for 5 min. Freshly

distilled acetaldehyde (44 ml, 0.78 mmol) was added

dropwise and the mixture was gradually warmed to

−40°C over a 30 min period and the mixture was

stirred an additional 30 min at −40°C upon which

time the solution became dark red. Acetic acid (31 ml,

0.55 mmol) was injected and the mixture was quickly

warmed to r.t. and concentrated on a rotary evapora-

tor. The remaining residue was chromatographed on

silica gel with CH₃CNꢀEt₂O (1:2, R_f=0.65) to give the

crude aldol adduct (156 mg, 95%) as a red solid which

was immediately taken up in 20 ml of CH₂Cl₂at r.t.

under argon. Triethylamine (28 ml, 0.20 mmol) was then

added by syringe and the mixture was stirred for 2

1

(CH₂Cl₂); H-NMR (CDCl₃) l 2.55 (s, 3H), 4.46 (m,

2H), 4.47 (m, 2H); ¹³C-NMR was not obtained due to

the rapid decomposition in all deuterated solvents; IR

(neat) cm⁻¹2927w, 2179s, 2060s, 1992s, 1924s, 1792s,

1383m, 1348s, 1320s, 1208m, 1175s, 1045m; mass spec-

trum (EI): m/z (relative intensity) 301 (1) M⁺, 272 (1),

257 (1), 239 (1), 220 (100), 209 (1), 192 (19), 164 (19),

136 (26), 108 (100); m/z calc. for C₁₁H₇CrNO₆

300.9678, measured 300.9675.

198

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

h at r.t. Acetic acid (23 ml, 0.40 mmol) was added and

the resulting purple solution was concentrated to about

2 ml and chromatographed on silica gel with CH₂Cl₂

(R_f=0.43) to give 81 mg of 52 as a reddish–purple

solid in 60% yield from 20. Spectral data for 52: m.p.

aldehyde (79 ml, 0.78 mmol) was added dropwise. The

reaction mixture was gradually warmed to 0°C over a

30 min period and stirred at this temperature for an

additional 30 min. Acetic acid (0.31 ml, 0.55 mmol) was

then added and the reaction mixture was immediately

warmed to r.t. and stripped of solvent on a rotary

evaporator. The remaining residue was ﬁltered through

a short plug of Celite with 20 ml of CH₂Cl₂. Triethyl-

amine (50 ml, 36 mmol) was then injected into this

ﬁltrate and the mixture was stirred under nitrogen for 1

h. The solution was concentrated to about 3 ml and

was chromatographed on silica gel with CH₂Cl₂(R_f=

0.50) to give 151 mg of the title compound as a deep

blue solid in 76% yield. Spectral data for 54: m.p.

1

130°C (dec.); H-NMR (500 MHz, CDCl₃) l 2.16 (d,

3H, J=6.7 Hz), 3.00 (s, 3H), 3.88 (t, 2H, J=8.0 Hz),

3.98 (t, 2H, J=8.0 Hz), 6.67 (d, 1H, J=14.4 Hz), 7.75

(dq, 1H, J=14.4, 7.1 Hz); ¹³C-NMR (500 MHz, ace-

tone-d₆, −50°C) l 20.77, 30.61, 42.75, 48.79,136.80,

159.10, 163.65, 217.20, 231.59, 232.03, 291.83; ¹³C-

NMR (500 MHz, CD₂Cl₂) l 21.06, 31.27, 41.97,

48.74,136.26, 158.23, 163.38, 217.21, 232.07, 232.54,

297.90; IR (neat) 2001 vs, 1879 vs, 1828 vs, 1712 s, 1376

m, 1384 m cm⁻¹; mass spectrum, FAB (3-NBA), m/z

(relative intensity) 316 M⁺(60), 307 (10), 288 (8), 260

(20), 232 (25), 204 (5), 154 (100), 136 (80), 107 (25);

Calc. for C₁₂H₁₂N₂O₅Cr, FAB (3-NBA), m/z 316.0152,

measured 316.0154. Anal. Calc. for C₁₂H₁₂N₂O₅Cr: C,

45.58; H, 3.82; N 8.86. Found: C, 45.62; H, 4.05; N,

8.51%.

1

131°C (dec.); H-NMR (500 MHz, CD₂Cl₂) l 3.02 (s,

3H), 3.90 (t, 2H, J=6.8 Hz), 4.09 (t, 2H, J=7.1 Hz),

7.36 (d, 1H, J=15.0 Hz), 7.46–7.74 (m, 5H), 8.47 (d,

1H, J=15.0 Hz); ¹³C-NMR (500 MHz, CD₂Cl₂) l

31.36, 42.06, 48.83, 129.43, 129.55, 129.76, 130.23,

131.64, 155.58, 160.11, 217.65, 232.42, 233.36, 296.29;

IR (neat) 1997 s, 1873 vs, 1815 s, 1709 s, 1363 m cm⁻¹

;

mass spectrum, FAB (3-NBA), m/z (relative intensity)

378 (42) M⁺, 350 (13), 322 (13), 307 (25), 289 (10), 266

(2), 154 (100). Anal. Calc. for C₁₇H₁₄N₂O₅Cr: C, 53.98;

H, 3.73; N, 7.41. Found: C, 53.98; H, 3.72; N, 7.42%.

4.19. Preparation of [trans-propenyl

[3-(1-methyl-2-imidazolidone)]methylene]

tetracarbonyltungsten (0) (53)

Complex 53 was prepared according to the procedure

described above for complex 52 from the methyl com-

plex 21 (207 mg, 0.49 mmol). After addition of triethyl-

amine, the solution was stirred for 45 min and then the

purple solution was concentrated to ꢀ2 ml and the

crude product was chromatographed with CH₂Cl₂

(R_f=0.41) to give 150 mg of 53 as a reddish–purple

solid in 62% from 21. Spectral data for 53: m.p. 115°C

(dec.): ¹H-NMR (500 MHz, CDCl₃) l 2.04 (d, 3H,

J=7.2 Hz), 3.09 (s, 3H), 3.96–4.02 (m, 4H), 6.53 (d,

1H, J=14.3 Hz), 8.00 (dq, 1H, J=14.2, 6.9 Hz);

¹³C-NMR (75 MHz, acetone-d₆, −50°C) l 20.92,

30.89, 43.08, 48.70, 137.96, 162.80, 166.77, 217.20,

219.79, 225.83, 272.85; IR (neat) 2002 (s), 1902 (vs),

1864 (vs), 1816 (vs), 1702 (s), 1374 (m), 1299 (m), 1224

(m) cm⁻¹; mass spectrum, FAB (3-NBA), m/z (relative

4.21. Preparation of [trans-i-styryl-[3-(1-methyl-2-

imidazolidinone)]methylene] tetracarbonyltungsten (0)

(55)

Complex 55 was prepared from complex 21 (200 mg,

0.47 mmol) according to the procedure described for 54

except that triethylamine was not used. Puriﬁcation of

the product on silca gel (R_f=0.65, CH₂Cl₂) gave 157

mg of the aldol condensation product 55 in 65% yield

as a prussian blue solid. The aldol addition product was

also isolated in 10% yield. Spectral data for 55: m.p.

1

80°C (dec.); H-NMR (500 MHz, CD₂Cl₂) l 3.11 (s,

3H), 4.02 (t, 2H, J=7.7 Hz), 4.09 (t, 2H, J=7.7 Hz),

7.22 (d, 1H, J=14.9 Hz) 7.35–7.56 (m, 3H), 7.80 (d,

2H, J=7.6 Hz), 8.71 (d, 1H, J=15.0 Hz); IR (neat)

1991 (s), 1869 (vs), 1808 (s), 1696 (s) cm⁻¹; mass

spectrum, FAB (3-NBA), m/z (relative intensity) 510

intensity) 448 M^{+ 184}W, 10), 419 (5), 391 (3), 363 (2),

(

341 (5), 327 (2), 154 (100), 136 (80); Calc. for

C₁₂H₁₂N₂O¹₅⁸⁴W, FAB (3-NBA), m/z 448.0256, mea-

sured 448.0238.

M^{+ 184}W, 40), 495 (30), 460 (55), 427 (70), 391 (75),

(

371 (25), 154 (100); Calc. for C₁₇H₁₄N₂O¹₅⁸⁴W, FAB

(3-NBA), m/z 509.9402, measured 510.0403.

4.20. Preparation of [trans-i-styryl-[3-(1-methyl-

2-imidazolidinone)]methylene] tetracarbonylchromium

(0) (54)

4.22. Preparation of [ethyl [3-(1-methyl-2-

imidazolidinone)]methylene] tetracarbonylchromium (0)

(56)

A solution of complex 20 (150 mg, 0.52 mmol) in 5

ml of THF was cooled to −78°C under an atmosphere

of argon. A 1.6 M solution of n-BuLi (0.34 ml, 0.54

mmol) in hexanes was added and the yellow solution

was stirred for 5 min after which freshly distilled benz-

4.22.1. Method A

According to the procedure for the preparation of

complex 20, the carbene complex 56 was prepared from

the ammonium salt 67 and 1-methyl-2-imidazolidinone

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

199

19 in 7% yield as a dark red solid. Spectra data for 56:

m.p. 112°C (dec.); H-NMR (300 MHz, CD₂Cl₂) l 1.44

4.24. Preparation of [iso-propyl [3-(1-methyl-2-imidazo-

lidinone)]methylene] tetracarbonylchromium (0) (57)

1

(t, 3H, J=7.6 Hz), 2.98 (s, 3H), 3.18 (q, 2H, J=7.6

Hz), 3.88–3.97 (m, 4H); ¹³C-NMR (300 MHz, CD₂Cl₂)

l 12.20, 31.16, 40.34, 41.09, 48.85, 162.54, 216.30,

231.85, 231.97, 322.51; IR (neat) 2006 (s), 1875 (vs),

1816 (vs), 1717 (s), 1364 (m), 1300 (m) cm⁻¹; mass

spectrum, m/z (relative intensity) 304 M⁺(10), 276

(25), 220 (25), 192 (10) 154 (100); Calc. for

C₁₁H₁₂N₂O₅Cr, FAB (3-NBA), m/z 304.0151, measured

304.0153. Anal. Calc. for C₁₁H₁₂N₂O₅Cr: C, 43.43; H,

3.98; N, 9.21. Found: C, 43.02; H, 4.21; N, 9.00%.

Complex 56 (300 mg, 0.99 mmol) was dissolved in 8

ml THF and cooled to −78°C under an atmosphere of

argon. A 1.6 M solution of n-BuLi (0.65 ml, 1.04

mmol) in hexane was then added dropwise and the

resulting yellow solution was stirred for 5 min. Methyl

triﬂate (117 ml, 1.04 mmol) was then added via syringe

and the reaction mixture was allowed to warm to

−40°C in 30 min. After stirring at −40°C for 1 h, the

reaction was warmed to r.t. and the solvent was re-

moved on a rotary evaporator. Flash chromatography

on silica gel with CH₂Cl₂(R_f=0.62) gave 298 mg of 57

as a red solid in 95% yield. Spectral data for 57: m.p.

4.22.2. Method D

Complex 20 (280 mg, 0.97 mmol) was dissolved in 8

ml THF and cooled to −78°C under an atmosphere of

argon. A 1.6 M solution of n-BuLi (0.63 ml, 1.01

mmol) in hexanes was then added dropwise and the

resulting yellow solution was then transfered slowly via

cannula to a solution of methyl triﬂate (115 ml, 1.01

mmol) in 1 ml ether at −45°C. After 30 min, the

reaction was warmed to r.t. and the solvent was re-

moved on a rotary evaporator. Flash chromatography

on silica gel with CH₂Cl₂(R_f=0.62) gave 287 mg of

alkylated product which consists of 83 mol% of 56

(81% yield) and 8 mol% of 57 (7% yield) and a 9%

recovery of the starting material 20 as indicated by

¹H-NMR. These three carbene complexes are insepara-

ble on silica gel.

1

111°C (dec.); H-NMR (500 MHz, CDCl₃) l 1.53 (d,

6H, J=6.5 Hz), 2.96 (heptet, 1H, J=6.5 Hz), 3.02 (s,

3H), 3.92 (t, 2H, J=7.1 Hz), 4.00 (t, 2H, J=7.1 Hz);

¹³C-NMR (300 MHz, CD₂Cl₂) l 22.13, 31.28, 41.63,

45.35, 48.42, 162.23, 216.37, 231.74, 232.02, 326.58; IR

(neat) 2006 (s), 1866 (vs), 1807 (vs), 1728 (s), 1514 (m),

1461 (m), 1399 (m), 1306 (m) cm⁻¹; mass spectrum,

m/z (relative intensity) 318 M⁺(27), 290 (8), 262 (5),

234 (23) 206 (98), 191 (15), 164 (24), 164 (24), 151 (99),

139 (67); Calc. for C₁₂H₁₄N₂O₅Cr, m/z 318.0308, mea-

sured 318.0359.

4.25. Preparation of [1-methyl-2-methoxyethyl-

[3-(1-methyl-2-imidazolidinone)]methylene]

4.23. Preparation of [ethyl[3-(1-methyl-2-

imidazolidinone)]methylene] tetracarbonyltungsten (0)

(58)

tetracarbonylchromium (0) (60) and [1-methoxy-

methyl-2-methoxyethyl[3-(1-methyl-2-imidazolidinone)]-

methylene] tetracarbonylchromium (0) (61)

4.23.1. Method A

A 264 mg (0.87 mmol) portion of the slightly impure

56 prepared by method D [20 (9%), 56 (83%) and 57

(8%)] was dissolved in 8 ml of THF and cooled to

−78°C under an atmosphere of argon. A 1.6 M solu-

tion of n-BuLi (0.57 ml, 0.91 mmol) in hexanes was

then added dropwise and the resulting yellow solution

was stirred for 5 min. Bromomethyl methyl ether [29]

(114 ml, 1.04 mmol) was then added via syringe and the

reaction mixture was stirred at −78°C for 2 h. The

reaction was warmed to r.t. over a 1 h period and the

solvent was removed on a rotary evaporator. Flash

chromatography on silica gel with CH₂Cl₂gave 20 mg

of 57 (R_f=0.62, 8% overall yield from 20) and 191 mg

of 60 (R_f=0.10, 62% overall yield from 20), further

eluting with ethyl acetate gave 30 mg of 61 (R_f=0.34,

9% overall yield from 20). Spectral data for 60: red

According to the procedure for complex 20, the

carbene complex 58 was prepared from the ammonium

salt 68 and 1-methyl-2-imidazolidinone 19 in 10% yield

as a dark red solid. Spectral data for 58: m.p. 121°C

(dec.); ¹H-NMR (300 MHz, CD₂Cl₂) l 1.45 (t, 3H,

J=7.5 Hz), 2.82 (q, 2H, J=7.5 Hz), 3.07 (s, 3H),

3.87–4.04 (m, 4H); ¹³C-NMR (300 MHz, CD₂Cl₂) l

13.40, 31.31, 41.46, 41.95, 48.66, 165.40, 204.45, 216.32,

221.41, 301.97; IR (neat) 2006 (s), 1869 (vs), 1810 (vs),

1714 (s), 1389 (m), 1301 (m) cm⁻¹; mass spectrum, m/z

(relative intensity) 436 M⁺(15, ¹⁸⁴W), 352 (50), 322

(45), 296 (30) 268 (65), 240 (35), 212 (35), 165 (35), 140

(90); Calc. for C₁₁H₁₂N₂O¹₅⁸⁴W, m/z 436.0256, mea-

sured 436.0267.

1

4.23.2. Method D

solid, m.p. 110°C (dec.); H-NMR (300 MHz, CD₂Cl₂)

According to the Method D for the preparation of

complex 56, the tungsten carbene complex 58 was pre-

pared from complex 21 by alkylation in 86% yield as a

dark red solid. The ¹H-NMR indicated that trace

amount of the dialkylated product 59 was also present.

l 1.43 (d, 3H, J=7.7 Hz), 2.98 (s, 3H), 3.12–3.19 (m,

1H), 3.31 (s, 3H), 3.69–3.73 (m, 1H), 3.88 (t, 1H,

J=7.7 Hz), 3.95–4.11 (m, 4H); ¹³C-NMR (300 MHz,

CD₂Cl₂) l 16.90, 31.22, 42.25, 48.33, 50.67, 58.79,

78.57, 162.05, 215.87, 216.38, 231.79 (2C), 323.55; IR

200

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

(neat) 2006 (s), 1884 (vs), 1817 (vs), 1721 (s), 1394 (m),

1302 (m), 1106 (m) cm⁻¹; mass spectrum, m/z (relative

intensity) 348 M⁺(34), 303 (35), 289 (10), 264 (15), 236

(100), 220 (20) 204 (63), 191 (55), 151 (75), 125 (44);

Calc. for C₁₃H₁₆N₂O₆Cr, m/z 348.0414, measured

348.0377. Spectral data for 61: red solid, m.p. 93°C

(dec.); ¹H-NMR (300 MHz, CD₂Cl₂) l 2.98 (s, 3H), 3.32

(s, 6H), 3.28–3.42 (m, 1H), 3.87–3.82 (m, 4H), 3.99 (t,

2H, J=8.7 Hz), 4.09 (t, 2H, J=7.8 Hz); ¹³C-NMR (300

MHz, CD₂Cl₂) l 31.20, 42.60, 48.34, 57.17, 58.97, 74.28,

161.99, 215.92 (2C), 231.57, 231.66, 320.51; IR (neat)

2006 (s), 1885 (vs), 1815 (vs), 1720 (s), 1395 (m), 1301

(m), 1106 (m) cm⁻¹; mass spectrum, m/z (relative

intensity) 378 M⁺(15), 266 (75), 234 (18), 220 (50) 204

(25), 191 (40), 167 (22), 151 (38), 108 (60); Calc. for

C₁₄H₁₈N₂O₇Cr, m/z 378.0519, measured 378.0477.

¹H-NMR (300 MHz, CD₂Cl₂) l 2.17 (s, 3H), 2.99 (s,

3H), 3.82–3.96 (m, 4H), 4.69 (s, 1H), 4.97 (s, 1H);

¹³C-NMR (300 MHz, CD₂Cl₂) l 20.77, 31.23, 41.83,

49.02, 105.90, 151.77, 162.44, 216.22, 231.68, 232.92,

314.79; IR (neat) 2007 (s), 1874 (vs), 1823 (vs), 1717 (s),

1375 (m), 1300 (m), 1252 (m) cm⁻¹; mass spectrum, m/z

(relative intensity) 316 M⁺(13), 288 (6), 256 (11), 232

(12), 220 (100), 204 (73), 192 (7), 164 (27), 154 (24);

Calc. for C₁₂H₁₂N₂O₅Cr, m/z 316.0151, measured

316.0149. Anal. Calc. for C₁₂H₁₂N₂O₅Cr: C, 45.58; H,

3.82; N, 8.86. Found: C, 45.20; H, 4.20; N, 8.95.

4.28. Preparation of [iso-propenyl[3-(1-methyl-

2-imidazolidinone)]methylene] tetracarbonyltungsten (0)

(65)

According to the procedure for complex 64, the

tungsten carbene complex 65 was prepared from com-

plex 62 by dehydration and obtained as a dark brown

solid in 85% yield. Spectral data for 65: m.p. 143°C

(dec.); ¹H-NMR (300 MHz, CD₂Cl₂) l 2.15 (s, 3H), 3.08

(s, 3H), 3.86–3.99 (m, 4H), 4.76 (s, 1H), 4.99 (s, 1H);

¹³C-NMR (300 MHz, CD₂Cl₂) l 21.32, 31.39, 42.31,

48.94, 107.62, 152.16, 165.71, 204.50, 216.04, 222.29,

292.90; IR (neat) 2008 (s), 1877 (vs), 1820 (vs), 1709 (s),

1371 (m), 1259 (m) cm⁻¹; mass spectrum, m/z (relative

intensity) 448 M⁺(13, ¹⁸⁴W), 420 (5), 352 (77), 336 (43),

296 (65), 270 (100), 240 (70), 212 (70), 198 (24), 184 (47);

Calc. for C₁₂H₁₂N₂O₅¹⁸⁴W, m/z 448.0256, measured

448.0221. Anal. Calc. for C₁₂H₁₂N₂O₅W: C, 32.17; H,

2.70; N, 6.25. Found: C, 31.80; H, 3.12; N, 6.31%.

4.26. Preparation of [1-methyl-2-methoxyethyl-

[3-(1-methyl-2-imidazolidinone)]methylene]

tetracarbonyltungsten (0) (62)

Carbene complex 62 was prepared from 58 (300 mg,

0.69 mmol) by the procedure described above for the

preparation of complex 60. The product was obtained in

80% yield (263 mg, R_f=0.10) as a red solid. No

dialkylation products could be detected. Spectral data

for 62: m.p. 126°C (dec.); ¹H-NMR (300 MHz, CD₂Cl₂)

l 1.34 (d, 3H, J=6.7 Hz), 2.98–3.06 (m, 1H), 3.07 (s,

3H), 3.28 (s, 3H), 3.65 (dd, 1H, J=13.0, 4.6 Hz),

3.84–4.13 (m, 5H); ¹³C-NMR (300 MHz, CD₂Cl₂) l

17.53, 31.37, 42.68, 48.16, 50.90, 58.81, 79.02, 165.27,

204.00, 204.57, 216.73, 220.94, 303.26; IR (neat) 2005

(s), 1869 (vs), 1806 (vs), 1715 (s), 1450 (m), 1392 (m),

1301 (m), 1258 (m) cm⁻¹; mass spectrum, m/z (relative

intensity) 480 M⁺(30, ¹⁸⁴W), 480 (24), 366 (25), 350

(24), 324 (20), 298 (23), 268 (34), 240 (18), 204 (25), 184

(33), 169 (25), 153 (38); Calc. for C₁₃H₁₆N₂O¹₆⁸⁴W, m/z

480.0518, measured 480.0492. Anal. Calc. for

C₁₃H₁₆N₂O₆W: C, 32.52; H, 3.36; N, 5.84. Found: C,

32.18; H, 3.80; N, 6.11%.

4.29. Preparation of [2-(3-methoxypropene)-

[3-(1-methyl-2-imidazolidinone)]methylene]

tetracarbonylchromium (0) (66)

According to the procedure for complex 64, the

carbene complex 66 was prepared from complex 61 by

dehydration and obtained as a dark brown solid in 85%

1

yield. Spectral data for 66: m.p. 89°C (dec.); H-NMR

(300 MHz, CD₂Cl₂) l 3.01 (s, 3H), 3.41 (s, 3H), 3.88 (t,

2H, J=8.4 Hz), 4.01 (t, 2H, J=8.0 Hz), 4.44 (s, 2H),

4.74 (s, 1H), 5.07 (s, 1H); ¹³C-NMR (300 MHz, CD₂Cl₂)

l 31.22, 42.26, 49.01, 58.89, 75.85, 105.20, 153.44,

162.32, 215.98, 231.77, 232.80, 312.69; IR (neat) 2007

(s), 1884 (vs), 1825 (vs), 1717 (s), 1377 (m), 1300 (m)

cm⁻¹; mass spectrum, m/z (relative intensity) 346 M⁺

(15), 262 (15), 234 (89), 220 (87), 204 (70), 178 (25), 167

(15), 151 (35), 136 (15), 108 (85); Calc. for

C₁₃H₁₄N₂O₆Cr, m/z 346.0257, measured 346.0221.

4.27. Preparation of [iso-propenyl[3-(1-methyl-2-

imidazolidinone)]methylene] tetracarbonylchromium (0)

(64)

Carbene complex 60 (175 mg, 0.50 mmol) was dis-

solved in 3 ml of CH₂Cl₂and 20 ml of Et₂O under an

atmosphere of argon. Alumina (1.54 g, ICN Alumina

B-Super 1) was added in one portion and the mixture

was stirred at r.t. for 3 h, upon which time the TLC

showed that all the starting carbene complex had disap-

peared. The mixture was ﬁltered and washed with

CH₂Cl₂and the solvent removed in vacuo and the dark

residue was chromatographed on silica gel with CH₂Cl₂

to give 127 mg of 64 (R_f=0.66) as a dark purple solid

in 80% yield. Spectral data for 64: m.p. 85°C (dec.);

4.30. Preparation of [methyl[(4R,5S)-1,5-dimethyl-

4-phenyl-2-imidazolidone]methylene] tetracarbonyl-

chromium (0) (72)

Tetramethylammonium(1-hydroxy-ethylidene) penta-

carbonylchromium (0) 15 [25] (1.50 g, 4.85 mmol) was

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

201

dissolved in 15 ml CH₂Cl₂under an atmosphere of

argon and cooled to −70°C. Freshly distilled acetyl

bromide (0.36 ml, 4.85 mmol) was then added dropwise

and the remaining solution was stirred for an additional

60 min upon which time a solution of (4R,5S)-1,5-

dimethyl-4-phenyl-2-imidazolidone 70 [19] (0.92 g, 4.85

mmol) in 10 ml CH₂Cl₂was added dropwise. The

mixture was gradually warmed to −60°C over a 15

min period and was stirred at this temperature for 18 h.

The mixture was quickly warmed to r.t. and concen-

trated on a rotary evaporator to remove two-thirds of

the solvent. The resulting reddish–brown solution was

loaded onto a silica gel column and the product eluted

with CH₂Cl₂(R_f=0.63) to give complex 72 as a red

solid. Further recrystallization from CH₂Cl₂and pen-

tane afforded 0.84 g of 72 as deep-red prisms in 65%

yield. Shorter reaction times (−45°C, 2 h) leads to

reduced yields (44%). Spectral data for 72: m.p. 117°C

(dec.); ¹H-NMR (500 MHz, CDCl₃) l 0.85 (d, 3H,

J=6.7 Hz), 2.78 (s, 3H), 2.94 (s, 3H), 4.40–4.48 (m,

1H), 5.35 (d, 1H, J=8.5 Hz), 7.08 (br s, 3H), 7.41 (t,

2H, J=5.5 Hz); ¹³C-NMR (300 MHz, CDCl₃) l 14.84,

28.43, 34.35, 59.98, 61.79, 126.36, 128.35, 129.24,

133.85, 162.32, 215.21, 215.49, 231.62 (2C), 320.87;

¹³C-NMR (75 MHz, acetone-d₆, −50°C) l 14.73,

28.45, 30.04, 34.14. 60.45, 62.02, 125.65, 129.41, 129.83,

135.56, 163.12, 216.14, 216.21, 213.74, 232.45, 317.35;

IR (neat) 2007 (s), 1982 (shoulder, s), 1900 (vs), 1827

(s), 1711 (s), 1355 (m), 1148 (m) cm⁻¹; mass spectrum,

m/z (relative intensity) 380 M⁺(10), 268 (5), 244 (25),

230 (15), 220 (100), 203 (40), 132 (40), 118 (30), 108

(95), 80 (100). Anal. Calc. for C₁₇H₁₆O₅N₂Cr: C, 53.68;

H, 4.24; N, 7.37. Found: C, 53.31; H 4.24; N, 7.20%.

C₁₇H₁₆N₂O¹₅⁸²W, FAB (3-NBA), m/z 510.0542, mea-

sured 510.0594. Anal. Calc. for C₁₇H₁₆O₅N₂W: C,

39.87; H, 3.15; N, 5.47. Found: C, 39.48; H, 3.50; N,

5.20%.

4.32. Preparation of [methyl[(4R,5S)-1,5-dimethyl-

4-cyclohexyl-2-imidazolidinone]methylene]

tetracarbonylchromium (0) (74)

According to the procedure for complex 72, the

carbene complex 74 was prepared from the ammonium

salt 15 [21] and (4R,5S)-1,5-dimethyl-4-cyclohexyl-2-im-

idazolidinone 71 [19c] and obtained in 10% yield as a

dark red solid. Spectral data for 74: m.p. 77°C (dec.);

¹H-NMR (300 MHz, CDCl₃) l 0.80–1.25 (m, 5H), 1.41

(d, 3H, J=6.6 Hz), 1.56–2.01 (m, 6H), 2.86 (s, 3H),

3.16 (s, 3H), 4.05–4.46 (m, 2H); ¹³C-NMR (300 MHz,

CDCl₃) l 12.61, 25.78, 25.87, 26.61, 27.97, 28.28, 32.29,

35.46, 40.25, 59.66, 63.21, 163.04, 215.24, 215.61,

231.32, 231.74, 318.75; IR (neat) 2934 (m), 2857 (m),

2005 (s), 1882 (vs), 1826 (vs), 1711 (s), 1358 (m), 1141

(m) cm⁻¹; Anal. Calc. for C₁₇H₂₂N₂O₅Cr: C, 52.85; H,

5.74; N, 7.25. Found: C, 52.68; H, 6.38; N, 7.10%.

4.33. Preparation of [methyl[(4R,5S)-1,5-dimethyl-4-

cyclohexyl-2-imidazolidinone]methylene]

tetracarbonyltungsten (0) (75)

According to the procedure for complex 72, the

carbene complex 75 was prepared from the ammonium

salt 16 [26] and (4R,5S)-1,5-dimethyl-4-cyclohexyl-2-im-

idazolidinone 71 [19c] in 25% yield as a dark red solid.

1

Spectral data for 75: m.p. 75°C (dec.); H-NMR (300

MHz, CD₂Cl₂) l 0.86–0.99 (m, 2H), 1.04–1.39 (m,

3H), 1.44 (d, 3H, J=6.5 Hz), 1.51–1.90 (m, 6H), 2.94

(s, 3H), 2.96 (s, 3H), 4.19–4.448 (m, 2H); ¹³C-NMR

(300 MHz, CD₂Cl₂) l 12.98, 26.30, 26.31, 27.03, 28.39,

29.05, 32.85, 37.31, 40.35, 60.08, 64.16, 164.49, 213.44,

206.61, 216.89, 221.10, 297.80; IR (neat) 2933 (m), 2856

(m), 2006 (s), 1874 (vs), 1818 (vs), 1704 (s), 1358 (m)

cm⁻¹. Anal. Calc. for C₁₇H₂₂N₂O₅W: C, 39.40; H, 4.28;

N, 5.41. Found: C, 39.00; H, 4.34; N, 5.41%.

4.31. Preparaton of [methyl[(4R,5S)-1,5-dimethyl-4-

phenyl-2-imidazolidone]methylene] tetracarbonyltungsten

(0) (73)

According to the procedure for complex 72, the

tungsten carbene 73 was prepared the ammonium salt

16 [26] and (4R,5S)-1,5-dimethyl-4-phenyl-2-imida-

zolidone 70 [19] and obtained in 50% yield as deep-red

prisms. Spectral data for 73: m.p. 115°C (dec.); ¹H-

NMR (500 MHz, CDCl₃) l 0.91 (d, 3H, J=6.5 Hz),

2.48 (s, 3H), 3.04 (s, 3H), 4.40–4.55 (m, 1H), 5.33 (d,

1H, J=8.5 Hz), 7.26–7.40 (m, 5H); ¹³C-NMR (300

MHz, CDCl₃) l 15.07, 28.64, 36.16, 60.06, 62.28,

127.97, 128.28, 129.43, 133.36, 165.55, 203.29, 204.30,

216.28, 221.40, 297.68; ¹³C-NMR (75 MHz, acetone-d₆,

−50°C) l 14.84, 28.70, 30.04, 35.72, 60.62, 62.57,

125.86, 129.59, 129.87, 135.03, 166.14, 204.24, 204.98,

216.39, 221.95, 296.51; IR (neat) 2008 (s), 1974 (shoul-

4.34. Preparation of (4S)-phenyl-1-

methyl-2-imidazolidone (79)

Compound 79 was prepared according to the proce-

dure that has been published for the synthesis of imida-

zolidinone 70 [19] The fusion of urea (1.34 g, 22.25

mmol) and (4R)-phenyl-3-methyl-ethylenediamine 78

[30] (1.38 g, 7.41 mmol) to gave 567 mg of 79 in 44%

yield as a white solid after chromatography with 9:1

EtOAc/MeOH (R_f=0.44). Spectral data for 79: m.p.

124–27°C; [h]_D−33.0° (c 1.00, MeOH); ¹H-NMR

(500 MHz, CDCl₃) l 2.77 (s, 3H), 3.17 (t, 1H, J=7.7

Hz), 3.73 (t, 1H, J=8.8 Hz), 4.69 (br t, 1H, J=7.8

der, s), 1909 (vs), 1824 (vs), 1704 (s), 1352 (m) cm⁻¹

;

mass spectrum, FAB (3-NBA), m/z (relative intensity)

512 M⁺(50, ¹⁸⁴W), 484 (38, ¹⁸⁴W), 456 (80, ¹⁸⁴W), 398

(18), 338 (55), 233 (75), 154 (100); Calc. for

202

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

Hz), 4.88 (br s, 1H), 7.25–7.32 (m, 5H); ¹³C-NMR (75

MHz, CDCl₃) l 30.02, 53.01, 55.54, 125.55, 127.34,

128.25, 141.58, 162.42; IR (neat) 3253 (m), 1699 (vs),

1493 (m), 1442 (w), 1254 (w) cm⁻¹; mass spectrum, m/z

(relative intensity) 176 M⁺(100), 132 (15), 118 (7), 104

(35), 9 (12), 91 (14), 77 (17). Anal. calc for C₁₀H₁₂N₂O:

C, 68.15; H, 6.87; N, 15.90. Found: C, 67.38; H, 7.13;

N, 16.50%.

though a plug of Celite. The solution was concentrated

on a rotary evaporator and the remaining residue was

chomatographed with CH₂Cl₂to give 0.93 g of complex

86-E (65%, R_f=0.51) and 0.13 g of complex 86--Z (9%,

R_f=0.42) as yellow solids in 74% combined yield.

Complex 86--E was isomerized as described in the

general procedure to give a 80:20 ratio of 86--Z to

86--E, respectively, in 87% combined yield after chro-

1

matography. The OH signal was not located by H-

4.35. Preparation of [methyl[(4R)-phenyl-2-

imidazolidone]methylene] tetracarbonylchromium (0)

(80)

NMR for either 86--E or 86--Z. Spectral data for 86--E:

m.p. 110–113°C; H-NMR (500 MHz, CDCl₃) l 1.17

1

(d, 3H, J=6.6 Hz), 1.96 (d, 3H, J=6.5 Hz), 4.26–4.28

(m, 1H), 4.87 (br s, 1H), 6.10 (dq, 1H, J=15.4, 6.7

Hz), 6.52 (d,1H, J=15.4 Hz), 7.40–7.30 (m, 5H), 8.82

(br s, 1H, NH); ¹³C-NMR (75 MHz, CDCl₃) l 15.44,

19.86, 59.87, 76.36, 126.46, 126.77, 129.37, 129.60,

137.37, 140.02, 218.77, 224.01, 271.80; IR (neat), 2053

The ammonium salt 15 [25] (352 mg, 1.14 mmol) was

dissolved in 7 ml CH₂Cl₂under an atmosphere of argon

and cooled to −60°C. Freshly distilled acetyl bromide

(84 ml, 1.14 mmol) was then added dropwise and the

remaining solution was stirred for an additional 30 min

upon which a solution of imidazolidone 79 (150 mg,

1.14 mmol) in 5 ml CH₂Cl₂was added dropwise. The

mixture was gradually warmed to −40°C over a 15

min period and was stirred at this temperature for 6 h.

The mixture was quickly warmed to r.t., ﬁltered

through a plug of Celite, and concentrated on a rotary

evaporator. The resulting reddish–brown residue was

chromatographed silica gel with CH₂Cl₂(R_f=0.64) to

give complex 80 as a red solid. Further recrystallization

from CH₂Cl₂and pentane afforded 271 mg of 80 as

deep-red prisms in 65% yield. Spectral data for 80: m.p.

(vs), 1970 (shoulder, vs), 1908 (vs), 1507 (s) cm⁻¹

.

Spectral data for 86--Z: m.p. 105–108°C; ¹H-NMR

(500 MHz, CDCl₃) l 1.23 (d, 3H, J=6.6 Hz), 1.87 (d,

3H, J=6.5 Hz), 4.66–4.68 (m, 1H), 5.16 (br s, 1H),

6.10 (dq, 1H, J=15.2, 6.7 Hz), 6.90 (d, 1H, J=15.1

Hz), 7.34–7.42 (m, 5H), 9.07 (br s, 1H, NH); ¹³C-NMR

(75 MHz, CDCl₃) l 13.04, 17.59, 62.98, 75.23, 123.17,

125.64, 128.24, 128.74, 139.86, 146.14, 217.84, 223.43,

262.54; IR (neat) 2054 (w), 1972 (shoulder, vs), 1917

(vs), 1529 (s), 1450 (m), 1394 (w) cm⁻¹; mass spectrum,

(mixture of rotamers), m/z (relative intensity) 395 M⁺

(15), 367 (25), 283 (45), 255 (100), 237 (15), 220 (10),

188 (15), 170 (25), 160 (35); Calc. for C₁₈H₁₇NO₆Cr,

FAB (3-NBA), m/z 395.0461, measured 395.0465.

1

94°C (dec.); H-NMR (500 MHz, CD₂Cl₂) l 2.79 (s,

3H), 2.99 (s, 3H), 3.59 (dd, 1H, J=10.0, 3.4 Hz), 4.29

(t, 1H, J=9.6 Hz), 5.28–5.32 (m, 1H), 7.14 (d, 2H,

J=7.1 Hz), 7.37–7.41 (m, 3H); ¹³C-NMR (75 MHz,

acetone-d₆, −50°C) l 30.66, 34.05, 57.51, 58.41,

126.40, 129.32, 130.11, 140.13, 162.98, 216.29, 218.30,

231.73, 237.46, 317.30; IR (neat) 2008 (s), 1879 (vs),

1825 (vs), 1717 (s), 1363 (m), 1251 (w) cm⁻¹; mass

spectrum, FAB (3-NBA), m/z (relative intensity) 366

M⁺(20), 307 (15), 289 (10), 154 (100), 136 (72), 107

(25); Calc. for C₁₆H₁₄O₅N₂Cr, FAB (3-NBA), m/z

366.0307, measured 366.0300.

4.37. Preparation of [trans-propenyl[(2R,1S)-

phenylmethyl-2-aminoethanol]methylene]

pentacarbonyltungsten (0) (87-E) and (87-Z)

Carbene complex 87 was prepared from the ammo-

nium salt 82 (1.00 g, 2.14 mmol) according to the

procedure above for the preparation of complex 86.

The product was puriﬁed by chromatograpy on silica

gel with CH₂Cl₂:Et₂O:hexane (1:1:2) to give 0.63 g of

complex 87-E (56%, R_f=0.54) and 0.16 g of complex

87-Z (14%, R_f=0.46) as yellow solids in 70% combined

yield. Complex 87-E was isomerized as described in the

general procedure to give a 80:20 ratio of 87-Z to 87-E,

respectively, in 85% combined yield after chromatogra-

4.36. Preparation of [trans-propenyl[(2R,1S)-

phenylmethyl-2-aminoethanol]methylene]

pentacarbonylchromium (0) (86-E) and (86-Z)

1

The ammonium salt 81 (1.00 g, 3.62 mmol) was

dissolved in 10 ml of CH₂Cl₂and cooled to −60°C

under an atmosphere of argon. Acetyl bromide (267 ml,

3.62 mmol) was injected dropwise over a 5 min period

and the resulting deep purple solution was stirred for

an additional 45 min. A solution of (1R,2S)-(−)-

norephedrine (0.55 g, 3.62 mmol) in 5 ml of CH₂Cl₂

was then added dropwise and the solution was warmed

to −40°C and stirred an additional 10 h. The yellow–

brown solution was quickly warmed to r.t. and ﬁltered

phy. The OH signal was not located by H-NMR for

either 87-E or 87-Z. Spectral data for 87-E: m.p. 116–

119°C; ¹H-NMR (500 MHz, CDCl₃) l 1.20 (d, 3H,

J=6.6 Hz), 2.01 (d, 3H, J=5.4 Hz), 4.22 (dq, 1H,

J=6.0, 3.2 Hz), 4.88 (br s, 1H), 6.50–6.53 (m, 2H),

7.34–7.42 (m, 5H), 8.60 (br s, 1H, NH); ¹³C-NMR (75

MHz, CDCl₃) l 14.68, 19.48, 58.82, 75.45, 125.72,

126.04, 128.70, 128.90, 136.84, 147.02, 199.19, 203.20,

248.84; IR (neat) 3351 (w), 2061 (vs), 1968 (shoulder,

vs), 1905 (vs), 1504 (s), 1452 (m) cm⁻¹. Spectral data

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

203

for 87-Z: m.p. 82–85°C; ¹H-NMR (500 MHz, CDCl₃) l

1.21 (d, 3H, J=6.7 Hz), 1.93 (d, 3H, J=6.5 Hz),

4.60–4.62 (m, 2H), 5.89 (dq, 1H, J=15.0, 6.7 Hz), 6.81

(d, 1H, J=15.2 Hz), 7.34–7.42 (m, 5H), 8.90 (br s, 1H,

NH); ¹³C-NMR (75 MHz, CDCl₃) l 13.13, 19.46, 58.82,

75.43, 125.72, 126.04, 128.82, 128.88, 139.83, 146.99,

198.38, 203.29, 242.70; IR (neat) 3280 (w), 2061 (vs),

cinol (0.31 g, 2.25 mmol) according to the procedure

above for the preparation of complex 86. The product

was puriﬁed by chromatography on silica gel with

CH₂Cl₂–Et₂O–hexane (1:1:2) to give 0.72 g of complex

89-E (57%, R_f=0.30) and 87 mg of complex 89-Z (14%,

R_f=0.21) as yellow–orange oils in 71% combined yield.

Complex 88-E was isomerized as described in the general

procedure to give a 67:33 ratio of 89-Z to 89-E, respec-

tively, in 87% combined yield after chromatography.

1969 (shoulder, vs), 1909 (vs), 1534 (s), 1451 (m) cm⁻¹

;

mass spectrum (mixture of rotamers), m/z (relative

intensity) 527 M⁺(20, ¹⁸⁴W), 499 (15), 443 (40), 415 (40),

1

The OH signal was not located by H-NMR for either

387 (75), 267 (40), 117 (100); Calc. for C₁₈H₁₇NO₆¹⁸⁴

W

1

89-E or 89-Z. Spectral data for 89-E: H-NMR (500

(mixture of rotamers) m/z 527.0569, measured 527.0545.

MHz, CDCl₃) l 1.94 (d, 3H, J=6.8 Hz), 4.00 (dd, 1H,

J=11.5, 4.5 Hz), 4.11 (dd, 1H, J=11.3, 2.9 Hz),

4.96–4.99 (m, 1H), 6.39 (d, 1H, J=15.4 Hz), 6.66 (dq,

1H, J=15.0, 6.6 Hz), 7.28–7.47 (m, 5H), 9.16 (br s, 1H,

NH); ¹³C-NMR (75 MHz, CDCl₃) l 19.08, 63.59, 65.59,

126.37, 128.61, 129.46, 136.95, 137.94, 147.10, 199.17,

202.96, 253.07; IR (neat), 3358 (w), 2061 (vs), 1968

4.38. Preparation of [trans-propenyl[(2R)-

phenyl-2-aminoethanol]methylene]

pentacarbonylchromium (0) (88-E) and (88-Z)

Carbene complex 88 was prepared from the ammo-

nium salt 81 (0.69 g, 2.05 mmol) and (R)-(−)-phenylgly-

cinol (0.28 g, 2.05 mmol) according to the procedure

above for the preparation of complex 86. The product

was puriﬁed by chromatography on silica gel with

CH₂Cl₂–Et₂O–hexane (1:1:2) to give 0.50 g of complex

88-E (64%, R_f=0.33) and 70 mg of complex 88-Z (9%,

R_f=0.21) as orange oils in 73% combined yield. Com-

plex 88-E was isomerized as described in the general

procedure to give a 75:25 ratio of 88-Z to 88-E, respec-

tively, in 85% combined yield after chromatography.

(shoulder, m), 1909 (vs), 1497 (s), 1064 (m) cm⁻¹

.

1

Spectral data for 89-Z: H-NMR (500 MHz, CDCl₃) l

1.89 (d, 3H, J=6.4 Hz), 4.11–4.15 (m, 2H), 5.46–5.49

(m, 1H), 5.88 (dq, 1H, J=15.0, 6.8 Hz), 6.92 (d, 1H,

J=15.1, Hz), 7.32–7.44 (m, 5H), 9.20 (br s, 1H, NH);

¹³C-NMR (75 MHz, CDCl₃) l 17.49, 65.39, 68.43,

126.70, 127.82, 128.51, 129.20, 136.72, 147.74, 198.12,

202.88, 249.07; IR (neat) 3400 (w), 2061 (s), 1970

(shoulder, m), 1908 (vs), 1531 (m) cm⁻¹; mass spectrum,

m/z (relative intensity) 513 M⁺(75, ¹⁸⁴W), 485 (30), 446

(20), 429 (95), 390 (40), 375 (90), 304 (40), 269 (100), 242

(90); Calc. for C₁₇H₁₅NO¹₆⁸⁴W m/z 513.0409, measured

513.0448.

1

The OH signal was not located by H-NMR for either

1

88-E or 88-Z. Spectral data for 88-E: H-NMR (500

MHz, CDCl₃) l 1.85 (d, 3H, J=7.0 Hz), 3.97 (br d, 1H,

J=10.4 Hz), 4.06 (br d, J=10.1 Hz, 1H), 4.97–5.00 (m,

1H), 6.24 (dq, 1H, J=15.2, 6.7 Hz), 6.43 (d, 1H,

J=14.3 Hz), 7.25–7.43 (m, 5H), 9.32 (br s, 1H, NH);

¹³C-NMR (75 MHz, CDCl₃) l 19.84, 64.06, 66.34,

126.92, 127.16, 129.25, 130.10, 137.88, 141.34, 218.80,

223.92, 275.08; IR (neat), 3360 (w), 2053 (s), 1971

4.40. Preparation of [trans-propenyl[(2S)-amino-

3-phenyl-propanol]methylene] pentacarbonyltungsten (0)

(90-E) and (90-Z)

(shoulder, vs), 1913 (vs), 1496 (m), 1062 (w) cm⁻¹

.

Carbene complex 90 was prepared from the ammo-

nium salt 82 (3.80 g, 8.31 mmol) and (S)-(−)-2-amino-

3-phenyl-1-propanol (1.23 g, 8.31 mmol) according to

the procedure above for the preparation of complex 86.

The product was puriﬁed by chromatography on silica

gel with CH₂Cl₂–Et₂O–hexane (1:1:2, R_f=0.23) to

give 3.34 g of complexes 90-E and 90-Z as an insepara-

ble mixture of rotamers (7:1, respectively) as a yellow

solid in 78% combined yield. This 7:1 mixture of 90-E

and 90-Z was isomerized as described in the general

procedure to give a 80:20 ratio of 90-Z to 90-E, respec-

tively, in 85% combined yield after chromatography.

1

Spectral data for 88-Z: H-NMR (500 MHz, CDCl₃) l

1.87 (d, 3H, J=6.6 Hz), 4.18–5.29 (m, 2H), 5.58–5.64

(m, 2H), 6.99 (d, 1H, J=15.6, Hz), 7.34–7.44 (m, 5H),

9.35 (br s, 1H, NH); ¹³C-NMR (75 MHz, CDCl₃) l

17.56, 65.67, 66.31, 122.90, 126.50, 128.44, 129.15,

136.70, 146.41, 217.42, 223.35, 268.57; IR (neat) 3275

(w), 2054 (s), 1973 (shoulder, vs), 1910 (vs), 1521 (m),

1054 (w) cm⁻¹; mass spectrum, m/z (relative intensity)

381 M⁺(10), 353 (15), 269 (30), 241 (35), 137 (40), 104

(100), 77 (30); Calc. for C₁₇H₁₅NO₆Cr m/z 381.0304,

measured 381.0257.

1

The OH signal was not located by H-NMR for either

4.39. Preparation of [trans-propenyl[(2R)-

phenyl-2-aminoethanol]methylene]

1

90-E or 90-Z. Spectral data for 90-E: H-NMR (500

MHz, CDCl₃) l 1.94 (d, 3H, J=6.4 Hz), 3.00 (dd, 1H,

J=13.8, 5.8 Hz), 3.08 (dd, 1H, J=13.9, 5.9 Hz),

3.84–3.92 (m, 2H), 4.27–4.29 (m, 1H), 6.21 (d, 1H,

J=15.1 Hz), 6.33 (dq, 1H, J=15.1, 6.7 Hz), 7.23–7.40

pentacarbonyltungsten (0) (89-E) and (89-Z)

Carbene complex 89 was prepared from the ammo-

nium salt 82 (1.00 g, 2.14 mmol) and (R)-(−)-phenylgly-

204

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

(m, 5H), 8.62 (br s, 1H, NH); ¹³C-NMR (75 MHz,

CDCl₃) l 18.88, 37.31, 61.31, 63.27, 127.26, 128.98,

129.32, 129.44, 137.39, 143.21, 199.15, 203.08, 252.18.

217.26, 220.60, 280.64; IR (neat) 2012 (vs), 1897 (vs),

1824 (vs), 1699 (s), 1393 (s), 1224 (s) cm⁻¹; mass

spectrum, FAB (3-NBA), m/z (relative intensity) 525

M⁺(20, ¹⁸⁴W), 469 (10), 367 (45), 307 (35), 230 (40),

154 (100); Calc. for C₁₈H₁₅NO¹₆⁸²W, FAB (3-NBA), m/z

523.0382, measured 523.0372.

1

Spectral data for 90-Z: H-NMR (500 MHz, CDCl₃) l

1.89 (d, 3H, J=6.7 Hz), 3.13 (d, 2H, J=7.6 Hz),

3.77–3.81 (m, 2H), 4.56–4.61 (m, 1H), 5.77 (dq, 1H,

J=15.2, 8.4 Hz), 6.79 (d, 1H, J=15.1 Hz), 7.26–7.35

(m, 5H), 8.70 (br s, 1H, NH); ¹³C-NMR (75 MHz,

CDCl₃) l 17.58, 36.77, 62.44, 65.82, 127.28, 127.82,

128.99, 129.46, 135.97, 147.66, 198.41, 202.82, 246.40;

IR (neat) 3400 (w), 2061 (s), 1970 (shoulder, m), 1908

(vs), 1531 (m) cm⁻¹; mass spectrum (mixture of ro-

tamers), m/z (relative intensity) 527 M⁺(12, ¹⁸⁴W), 499

(10), 443 (20), 415 (20), 387 (40), 270 (27), 162 (20), 114

(100); Calc. for C₁₈H₁₇NO¹₆⁸²W (mixture of rotamers)

m/z 525.0539, measured 525.0529.

4.43. Preparation of [trans-propenyl[(4R)-phenyl-

2-oxazolidinone]methylene] tetracarbonylchromium (0)

(93)

The oxazolidinone complex 93 was prepared accord-

ing to procedure starting with 200 mg (0.52 mmol) of

88-Z to give 135 mg (68%) of 93 as a reddish–purple

solid after puriﬁcation by chromatography on silica gel

with EtOAc–hexane (1:1, R_f=0.19). Spectral data for

1

93: m.p. 70°C (sub.); H-NMR (500 MHz, CD₂Cl₂) l

4.41. Preparation of [trans-propenyl[(4R)-

methyl-(5S)-phenyl-2-oxazolidinone]methylene]

tetracarbonylchromium (0) (91)

1.96 (d, 3H, J=7.2 Hz), 4.86 (dd, 1H, J=9.4, 4.3 Hz),

5.27 (t, 1H, J=10.0 Hz), 5.52 (dd, 1H, J=9.1, 4.2 Hz),

6.62 (d, 1H, J=14.9 Hz), 7.16–7.21 (m, 2H), 7.40–7.49

(m, 3H), 7.71 (dq, 1H, J=14.6, 6.4 Hz); ¹³C-NMR (75

MHz, acetone-d₆, −50°C) l 21.09, 60.19, 79.95,

126.71, 129.44, 130.07, 138.78, 139.26, 160.18, 216.55,

216.70, 231.98, 233.32, 305.30; IR (neat) 2011 (vs), 1909

The oxazolidinone complex 91 was prepared as de-

scribed in the general procedure with phosgene starting

with 0.68 g (1.42 mmol) of 86-Z to give 0.47 g of 91

after chromatography using EtOAc–hexane (1:1, R_f=

0.43) in 70% yield as a deep purple solid. Spectral data

(vs), 1835 (vs), 1713 (m), 1409 (m), 1205 (m) cm⁻¹

.

1

for 91: m.p. 68°C (dec.); H-NMR (500 MHz, CD₂Cl₂)

4.44. Preparation of [trans-propenyl[(4R)-phenyl-

2-oxazolidinone]methylene] tetracarbonyltungsten (0)

(94)

l 0.97 (d, 3H, J=6.2 Hz), 2.17 (d, 3H, J=5.9 Hz),

4.81–4.83 (m, 1H), 6.17 (d, 1H, J=6.2 Hz), 6.83 (d,

1H, J=14.0 Hz), 7.26–7.49 (m, 5H), 7.85 (dq, 1H,

J=13.8, 6.9 Hz); ¹³C-NMR (75 MHz, acetone-d₆,

−50°C) l 16.08, 21.09, 57.55, 87.95, 126.78, 129.32,

129.77, 133.47, 138.26, 160.01, 163.56, 212.55, 216.68,

232.27, 233.34, 305.07; IR (neat) 2010 (vs), 1907 (s),

1835 (s), 1714 (w), 1388 (s), 1239 (s) cm⁻¹; mass

spectrum, FAB (3-NBA), m/z (relative intensity) 393

M⁺(3), 337 (10), 309 (23), 281 (20), 255 (3), 219 (10),

186 (12), 154 (100); Calc. for C₁₈H₁₅NO₆Cr, FAB (3-

NBA), m/z 393.0305, measured 393.0290.

The oxazolidinone complex 94 was prepared accord-

ing to procedure from the Z-rotamer of 89 (140 mg,

0.27 mmol). The product was puriﬁed by rapid chro-

matography on silica gel with EtOAc–hexane (1:1,

R_f=0.26) to give 94 (89 mg, 68% yield) as a deep

purple solid. The isolated chelated complex 94 was

dissolved in a small amount of CH₂Cl₂and was slowly

crystallized by the dropwise addition of pentane. The

deep-red micro-crystalline solid obtained though this

procedure can be stored at −30°C under argon for

weeks with only slight decomposition. However, this

complex is best used immediately following its prepara-

4.42. Preparation of [trans-propenyl[(4R)-

methyl-(5S)-phenyl-2-oxazolidinone]methylene]

tetracarbonyltungsten (0) (92)

1

tion. Spectral data for 94: m.p. 73°C (dec.); H-NMR

(500 MHz, CD₂Cl₂) l 1.74 (d, 3H, J=7.0 Hz), 4.82

(dd, 1H, J=8.9, 4.0 Hz), 5.36 (t, 1H, J=8.8 Hz), 5.54

(dd, 1H, J=8.8, 5.0 Hz), 6.49 (d, 1H, J=14.9 Hz),

7.16 (d, 2H, J=7.1 Hz), 7.42–7.49 (m, 3H), 8.05 (dq,

1H, J=14.4, 7.1 Hz); ¹³C-NMR (75 MHz, acetone-d₆,

−50°C) l 21.47, 60.73, 79.91, 126.76, 129.63, 130.08,

138.08, 138.72, 140.18, 169.34, 204.32, 204.75, 216.98,

220.79, 280.78; IR (neat) 2013 (vs), 1898 (vs), 1824 (vs),

1698 (m), 1413 (m), 1217 (s) cm⁻¹; mass spectrum,

FAB (3-NBA), m/z (relative intensity) 511 M⁺

(35,¹⁸⁴W), 460 (20), 367 (5), 307 (75), 273 (5), 230 (5),

154 (100); Calc. for C₁₇H₁₃NO⁽₆¹⁸²⁾W, FAB (3-NBA),

m/z 509.0226, measured 509.0214.

The oxazolidinone complex 92 was prepared as de-

scribed in the general procedure starting with 0.75 g

(1.42 mmol) of 87-Z to give 0.51 g of 92 after chro-

matography using EtOAc–hexane (1:1, R_f=0.43) in

68% yield as a deep purple solid. Spectral data for 92:

1

m.p. 78–81°C (dec.); H-NMR (500 MHz, CD₂Cl₂) l

1.07 (d, 3H, J=6.9 Hz), 2.04 (d, 3H, J=6.7 Hz),

4.91–4.94 (m, 1H), 6.33 (d, 1H, J=7.3 Hz), 6.77 (d,

1H, J=14.6 Hz), 7.35–7.53 (m, 5H), 8.23 (dq, 1H,

J=14.1, 7.0 Hz); ¹³C-NMR (75 MHz, acetone-d₆,

−50°C) l 16.01, 21.45, 57.97, 88.05, 126.88, 129.30,

129.83, 133.45, 139.48, 163.91, 168.34, 204.64, 204.88,

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

205

4.45. Preparation of [trans-propenyl[(4S)-methylphenyl-

2-oxazolidinone]methylene] tetracarbonyltungsten (0)

(95)

7.37 (t, 2H, J=7.3 Hz), 9.41 (brs, 1H); ¹³C-NMR

(CDCl₃) l 21.7, 21.8, 23.9, 25.8, 63.7, 65.7, 114.8, 126.2,

128.5, 129.3, 137.7, 147.5, 217.8, 223.1, 285.9; IR (neat)

cm⁻¹3345w, 2935w, 2885w, 2861w, 2053s, 1972s,

1914s, 1502m, 1456w, 1056w, 755w; mass spectrum

(EI): m/z (relative intensity) 421 (3) M⁺, 393 (16), 365

(4), 337 (8), 321 (1), 309 (48), 303 (1), 292 (1), 281 (100),

274 (2), 263 (4), 257 (2), 249 (23), 241 (6), 227 (44), 220

(7), 213 (16); m/e calc. for C₂₀H₁₉CrNO₆421.0617,

measured 421.0619. Spectral data for 98-Z: R_f=0.22

The oxazolidinone complex 95 was prepared as de-

scribed in the general procedure starting with a 4:1

mixture(1.00 g, 1.89 mmol) of 90-Z to 90-E, respec-

tively, to give 0.45 g of 95 after chromatography using

EtOAc–hexane (1:1, R_f=0.26) in 45% yield (based on

starting amount of 90-Z) as a deep purple solid. Spec-

1

tral data for 95: m.p. 58°C (dec.); H-NMR (500 MHz,

(CH₂Cl₂); H-NMR (CDCl₃) l 1.72 (m, 2H), 1.80 (m,

CD₂Cl₂) l 1.95 (d, 3H, J=6.4 Hz), 3.05 (dd, 1H,

J=10.9, 3.0 Hz), 3.21 (dd, 1H, J=9.0, 5.3 Hz), 4.81–

4.93 (m, 3H), 6.72 (d, 1H, J=14.2 Hz), 7.10–7.41 (m,

5H), 8.21 (dq, 1H, J=14.3, 6.9 Hz); ¹³C-NMR (75

MHz, acetone-d₆, −50°C) l 21.53, 29.78, 58.13, 75.89,

128.23, 129.49, 130.52, 134.66, 139.64, 164.05, 168.96,

204.54, 205.08, 217.06, 220.31, 281.00; IR (neat) 2011

(vs), 1896 (vs), 1825 (vs), 1700 (s), 1415 (s), 1349 (s),

1249 (s), 1222 (s) cm⁻¹; mass spectrum, FAB (3-NBA),

m/z (relative intensity) 525 M⁺(35, ¹⁸⁴W), 460 (15), 367

(5), 307 (80), 273 (5), 230 (5), 154 (100); Calc. for

C₁₈H₁₅NO¹₆⁸²W, FAB (3-NBA), m/z 523.0382, mea-

sured 523.0380.

2H), 2.14 (m, 2H), 2.35 (m, 2H), 4.16 (m, 2H), 5.26 (m,

1H), 5.51 (m, 1H), 7.20 (d, 2H, J=8.2 Hz), 7.29–7.43

(m, 3H), 9.20 (brs, 1H); ¹³C-NMR (CD₂Cl₂) l 22.2,

22.8, 25.0, 28.3, 66.2, 67.1, 117.5, 127.3, 128.9, 129.6,

137.6, 142.2, 218.3, 224.1, 285.8; IR (neat) cm⁻¹

3343w, 2935m, 2053s, 1972s, 1915s, 1506m, 1499m,

1456w, 1449w, 1437w, 1072w, 1060w, 1056w, 756w.

4.46.2. Method C

A solution of the ammonium salt 96 (187.7 mg, 0.50

mmol) was dissolved in 5 ml CH₂Cl₂under an atmo-

sphere of argon and cooled to −70°C. Freshly distilled

acetyl bromide (one equivalent) was then added drop-

wise and the remaining solution was stirred for an

additional 60 min. to give a deep red solution. A

prechilled (at −100°C) solution of 68.6 mg of (−)-

(1R)-1-phenyl-1-amino-2-hydroxyethane) [(R)-(−)-2-

phenyl glycinol] (0.50 mmol, 1.0 eq) in 2 ml of CH₂Cl₂

was added dropwise via a cannula to the acetoxy

solution at −78°C. After stirring at −50°C for 3 h,

the reaction mixture was concentrated under reduced

pressure and chromatographed on a silica gel column

(size: 1.5×30 cm, gradient eluent: 0–100% CH₂Cl₂in

hexane) to provide 72.5 mg of 98 (34%) as a yellow oil

with a E:Z ratio of 13.0:1. When the reaction time was

extended to 17 h instead of 3h, 98 was obtained in 26%

yield with a E:Z ratio of 11.4:1.

4.46. Preparation of

[1-cyclohexenyl[(2R)-phenyl-2-aminoethanol]methylene]

pentacarbonylchromium (0) (98-E) and (98-Z)

4.46.1. Method C

A solution of 97 [31] (0.60–0.90 mmol) in 40 ml of

CH₂Cl₂was cooled to −78°C and transferred to a

solution of 1.0 eq of (R)-(−)-2-phenyl glycinol in 20 ml

of CH₂Cl₂at −78°C. The reaction mixture was stirred

at −78°C for 1 h, −40°C for 1h, and at 25°C for 1 h,

and was closely monitored with TLC analysis (CH₂Cl₂,

PMA). After the TLC analysis showed the complete

consumption of the starting material, the reaction mix-

ture was concentrated under reduced pressure, and the

residue was chromatographed on a silica gel column

(size: 1.5×30 cm, gradient eluent: 0–80% CH₂Cl₂in

hexane) to provide the desired amino complex 98 as a

yellow oil in 50–60% yield with E:Z ratio ]80:1.

When the reaction was carried out in the presence 10

drops of Et₃N, the yield and ratio remained the same.

When the reaction was carried out with 97 (0.20–1.1

mmol) in 2–3 ml THF at r.t., 98 was obtained in 79%

yield with a E:Z ratio of 19:1. At −10°C, the yield was

80–84% and the ratio was 21:1. At −78°C, the yield

was 91% and the ratio was ]50:1. At −100°C, the

yield was 90% and the ratio was ]50:1. Spectral data

4.46.3. Isomerizations of (98-E) to (98-Z)

A solution of 98 (E:Z 20–50:1) (0.12–0.43 mmol)

and 1.0 eq of the base in THF (0.20 M in 98) was

deoxygenated using freeze-pump-thaw method (3 cy-

cles, at −196/25°C), and was sealed under a blanket of

argon at the end of the last cycle. The mixture was

heated at 70°C for 24–72 h. After evaporation of the

solvent, the residue was chromatographed on a silica

gel column (size: 1.5×30 cm, eluent: CH₂Cl₂) to

provide the pure 98. The ratios were determined from

¹H-NMR analysis. In the presence of DMAP, 98 was

recovered in 44–51% yield with new E:Z ratios of

3.1–3.4:1. Also isolated was Cr(CO)₅-DMAP in 37–

40% yield: yellow solid, decomposition at 106–108°C,

1

for 98-E: R_f=0.43 (CH₂Cl₂); H-NMR (CDCl₃) l 1.56

1

(m, 3H), 1.62 (t, 1H, J=5.8 Hz), 1.81 (t, 1H, J=5.4

Hz), 2.04 (m, 3H), 3.97 (m, 2H), 4.86 (m, 1H), 5.00 (m,

1H), 7.20 (d, 2H, J=8.2 Hz), 7.30 (t, 1H, J=6.8 Hz),

R_f=0.90 (CH₂Cl₂); H-NMR (CDCl₃) l 2.99 (s, 6H),

6.31 (d, 2H, J=6.6 Hz), 7.96 (d, 2H, J=6.6 Hz);

¹³C-NMR (CDCl₃) l 39.2, 107.4, 153.9, 154.5, 214.8,

206

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

220.9; IR (neat) cm⁻¹2922w, 2917w, 1916s, 807m;

mass spectrum (EI): m/z (relative intensity) 314 (56)

M⁺, 286 (19), 281 (13), 270 (6), 258 (24), 253 (8), 243

(44), 229 (83), 218 (16), 211 (18), 202 (100), 192 (28),

187 (26). In the presence of DABCO at 38 h, the yield

was 62% and the ratio was 3.5:1, and at 72h, the yield

was 75% and the ratio was 5.0:1. In the presence of

4-pyrrolidine-pyridine at 48 h, the yield was 23% and

the ratio was 1.96:1, and at 24 h, the yield was 68% and

the ratio was 2.3:1.

dure described above for complex 52 from the methyl

complex 72 (715 mg, 1.88 mmol). The crude product

was puriﬁed on a silica gel column and eluted with

EtOAc/hexane (1:1, R_f=0.37) to give 488 mg of 101 as

a reddish–purple solid in 64% yield from 72. Spectral

data for 101: m.p. 73–74°C; ¹H-NMR (500 MHz,

CDCl₃) l 0.87 (d, 3H, J=6.7 Hz), 1.90 (d, 3H, J=6.7

Hz), 2.94 (s, 3H), 4.41 (br t, 1H, J=7.4 Hz), 5.39 (d,

1H, J=8.4 Hz), 6.49 (d, 1H, J=14.5 Hz), 7.03 (br s,

2H), 7.36–7.38 (m, 3H), 7.58 (dq, 1H, J=14.4, 7.3

Hz); ¹³C-NMR (75 MHz, acetone-d₆, −50°C) l 14.65,

20.85, 28.55, 60.05, 62.21, 125.93, 129.32, 129.60,

136.37, 137.27, 159.08, 164.44, 213.81, 217.24, 231.48,

232.65, 296.31; IR (neat) 2003 (vs), 1886 (vs), 1819 (vs),

1708 (vs), 1358 (s), 1287 (s), 1225 (m) cm⁻¹; mass

spectrum, FAB (3-NBA), m/z (relative intensity) 406

M⁺(20), 378 (10), 322 (100), 294 (55), 241 (22), 154

(70); Calc. for C₁₉H₁₈N₂O₅Cr, FAB (3-NBA), m/z

406.0621, measured 406.0617. Anal. Calc. for

C₁₉H₁₈N₂O₅Cr: C, 56.16; H, 4.47; N, 6.89. Found: C,

56.52; H, 4.74; N, 7.00%.

4.47. Preparation of [1-cyclohexenyl[(4R)-phenyl-

2-oxazolidinone]methylene] tetracarbonylchromium (0)

(100)

The oxazolidinone complex 100 was prepared as

described in the general procedure starting with 107.5

mg of 98 (0.255 mmol, E:Z 2.3:1) to give 17.7 mg of 100

(51% based on the amount of 98-Z isomer) as a dark

red ﬁlm after chromatography on a silica gel column

(size: 3×18cm, gradient eluent: 0–50% CH₂Cl₂–hex-

ane). Spectral data for 100: R_f=0.20 (50% CH₂Cl₂–

1

hexane); H-NMR (CDCl₃) l 1.12 (m, 1H), 1.33 (m,

1H), 1.42 (brt, 2H, J=5.2 Hz), 2.02 (m, 2H), 2.12 (m,

1H), 2.56 (m, 1H), 4.70 (dd, 1H, J=4.6, 9.1 Hz), 5.20

(t, 1H, J=9.0 Hz), 5.29 (m, 1H), 5.51 (dd, 1H, J=4.6,

8.8 Hz), 7.06 (d, 2H, J=7.5 Hz), 7.20–7.46 (m, 3H);

¹³C-NMR was not obtained due to the rapid decompo-

sition in all deuterated solvents; IR (neat) cm⁻¹2935w,

2931w, 2053s, 2017s, 1910s, 1848s, 1713m, 1408w,

1181m; mass spectrum (EI): m/z (relative intensity) 419

(7) M⁺, 393 (2), 363 (3), 335 (8), 307 (76), 281 (40), 271

(47), 257 (100), 249 (5), 227 (10), 220 (13), 213 (6), 198

(20), 184 (21), 177 (7); m/z calc. for C₂₀H₁₇CrNO₆

419.0461, measured 419.0457.When the E:Z ratio of the

starting complex was 3.0:1, the yield of 100 was 64%

(based on Z-isomer). When the ratio was \20:1, only

the chloroformate 99 was found in 30–68% yield. Spec-

tral data for 99: yellow oil, R_f=0.76 (CH₂Cl₂); ¹H-

NMR (CDCl₃) l 1.63 (m, 4H), 2.11 (m, 4H), 4.50 (dd,

1H, J=4.1, 11.7 Hz), 4.65 (dd, 1H, J=2.6, 11.7 Hz),

4.97 (brs, 1H), 5.29 (brt, 1H, J=5.0 Hz), 7.21 (d, 2H,

J=7.1 Hz), 7.42 (m, 3H), 9.00 (brs, 1H); ¹³C-NMR

(CDCl₃) l 21.7, 21.8, 23.9, 26.0, 61.3, 71.5, 115.6, 126.0,

129.4, 129.8, 134.8, 147.1, 198.2, 217.3, 224.7, 286.1; IR

(neat) cm⁻¹3342w, 2933w, 2054s, 1974s, 1919s, 1773m,

1497m, 1457w, 1139m; mass spectrum (EI): m/z (rela-

tive intensity) 483 (18) M⁺, 455 (66), 399 (27), 381 (27),

371 (100), 354 (11), 343 (54), 335 (13), 318 (4), 307 (51),

292 (9), 281 (38); m/z calc. for C₂₁H₁₈ClCrNO₇

483.0177, measured 483.0172.

4.49. Preparation of [trans-propenyl[(4R,5S)-1,5-

dimethyl-4-phenyl-2-imidazolidone]methylene]

tetracarbonyltungsten (0) (102)

Complex 102 was prepared according to the proce-

dure described above for complex 52 from the methyl

complex 73 (146 mg, 0.29 mmol). The product was

puriﬁed on a silica gel column and eluted with CH₂Cl₂

(R_f=0.53) to give 118 mg of 102 as a reddish–purple

solid in 81% yield from 73. Spectral data for 102: m.p.

1

115°C (dec.): H-NMR (500 MHz, CDCl₃) l 0.90 (d,

3H, J=6.8 Hz), 1.80 (d, 3H, J=7.0 Hz), 3.02 (s, 3H),

4.48–4.51 (m, 1H), 5.35 (d, 1H, J=8.9 Hz), 6.35 (d,

1H, J=14.5 Hz), 6.99 (br s, 2H), 7.33–7.38 (m, 3H),

7.83 (dq, 1H, J=14.3, 7.0 Hz); ¹³C-NMR (75 MHz,

acetone-d₆, −50°C) l 14.72, 21.08, 28.76, 60.06, 62.78,

126.05, 129.47, 129.57, 129.71, 135.94, 138.50, 163.72,

204.92, 205.75, 217.03, 220.18, 275.62; IR (neat) 2003

(vs), 1875 (vs), 1808 (vs), 1700 (s), 1360 (m), 1287 (m),

1228 (m) cm⁻¹; mass spectrum, FAB (3-NBA), m/z

(relative intensity) 538 M⁺(10, ¹⁸⁴W), 510 (5), 482 (8),

460 (3), 426 (5), 307 (20), 154 (100); Calc. for

C₁₉H₁₈N₂O¹₅⁸²W, FAB (3-NBA), m/z 536.0698, mea-

sured 536.0710.

4.50. Preparation of [phenyl[(4R,5S)-1,5-dimethyl-

4-phenyl-2-imidazolidinone]methylene]

tetracarbonylchromium(0) (106)

4.48. Preparation of [trans-propenyl[(4R,5S)-1,5-

dimethyl-4-phenyl-2-imidazolidone]methylene]

tetracarbonylchromium (0) (101)

A 100 ml ﬂask was charged with 400 mg (2.1 mmol)

(4R,5S)-1,5-dimethyl-4-phenyl-2-imidazolidinone

70

and dissolved in 20 ml THF at −78°C. A solution of

Complex 101 was prepared according to the proce-

n-BuLi (2.5 M in hexane, 0.84 ml, 2.1 mmol) was

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

207

Table 3

Crystallographic data for 45, 107, 35 and 106

(a) Crystal Parameters

Compound

45

107

35

106

Empirical formula

Formula weight

Crystal system

Space group

C₁₄H₁₁CrNO₆

341.24

Triclinic

C₁₄H₁₅CrNO₇

361.3

Monoclinic

P21/c

16.928(3)

8.447(l)

12.746(2)

C₁₁H₁₁CrNO₆

305.21

Triclinic

C₂₂H₁₈CrN₂O₅

442.38

Orthorhombic

P2₁2₁2₁

9.3248(7)

13.1515(12)

17.098(2)

(

P1

,

a (A)

7.9192(11)

8.4451(10)

12.185(2)

99.375(13)

97.677(10)

99.656(10)

781.7(2)

2

8.026(l)

9.257(7)

10.538(l)

70.082(9)

69.473(8)

70.298(8)

667.96(12)

2

,

b (A)

,

c (A)

h (°)

i (°)

105.45(l)

k (°)

3

,

V A

Z

1756.8(6)

4

2096.8(4)

4

Crystal color

Yellow

1.450

7.58

Yellow–green

1.366

6.82

Yellow

1.517

8.77

Dark red

1.401

5.81

D_calc(g cm⁻³

)

v(Mo−K_a), cm⁻¹

Temperature (K)

296

298

297

298

(b) Data Collection

Diffractometer

Siemens P4

Monochromator

graphite

,

Radiation (A)

2q scan range (°)

Mo−K_a(u=0.71073)

5–50

3389

2745

3/197

7-45

4-60

Reﬂections collected

Independent reﬂections

Standard/reﬂections

2900

2148

3/1 97

3314

2644

3/197

4324

4108

3/197

a

(c) Reﬁnement

R(F) %

4.01 ^a

11.06

0.03

0.28

14.7

7.89 ^b

9.98

0.00

0.53

6.4

3.82 ^a

11.69

0.03

0.41

15.3

5.05 ^b

10.47

0.04

0.35

15.1

R(wF²) %

D/d (max)

−3

,

D(r) eA

N_o/N_v

^aQuantity minimized=S wD₂; R=S D/S (F_o); R(w)=S wD^1/2/S (F_o·w^1/2), D=ꢀ(F_o−F_c)ꢀ

^bQuantity minimized=R(wF²)=S[w(F_o²−F_c²)²]/S[(wF²_o)²]^1/2; R=S D/S (F_o), D=ꢀ(F_o−F_c)ꢀ

cm⁻¹. Anal. Calc. for C₂₂H₁₈N₂O₅Cr: C, 59.72; H,

4.10; N, 6.33; Cr, 11.75. Found: C, 58.95; H, 4.21; N,

6.40; Cr, 12.59. m.p. 140°C (dec.); R_f=0.85 (CH₂Cl₂),

0.15 (1:1:4 CH₂Cl₂:Et₂O:hexane); black needles.

added via syringe, and the yellow solution of anion was

stirred for 10 min. A solution of phenylmethoxy pen-

tacarbonyl chromium(0) 40 [28] (624 mg, 2.0 mmol) in

20 ml THF was then added via cannula. The reaction

was stirred for an additional 20 min at −78°C, then

allowed to warm to r.t. while stirring for 15 h. The

product was obtained by concentrating the solution to

a black oil on the rotovap, then purifying the oil by

ﬂash chromatography on silica gel (CH₂Cl₂eluent). The

black band was collected and concentrated to a black

powder. The powder was recrystallized from CH₂Cl₂–

pentane to give the product as black needle-like crys-

tals. The structure of this complex was conﬁrmed by

X-ray diffraction. Yield: 479 mg (54%). Spectral data

5. Crystallograghic structural determination for

compounds 45, 107 (acetate of 43), 35 and 106

Crystallographic data for 45, 107, 35 and 106 have

been collected in Table 3. Crystals of 107 were very

weakly diffracting which considerably reduced

availability of data. Crystals were photographically

characterized and those of 45 and 35 were found to be

triclinic, those of 107 were monoclinic and those of 106

were orthorhombic. The two triclinic samples were

shown to be centrosymmetric by the successful solution

1

for 106: H-NMR (300 MHz, CD₂Cl₂): l 0.83 (d, 3H,

J=6.7 Hz), 3.00 (s, 3H), 4.46 (quintet, 1H, J=6.9 Hz),

5.35 (d, 1H, J=8.4 Hz), 7.18–7.24 (m, 10H); ¹³C-

NMR (75 MHz, CD₂Cl₂): l 14.34, 28.15, 59.64, 62.34,

121.50, 127.09, 127.45, 127.98, 128.24, 128.36, 134.35,

146.72, 163.07, 215.35, 216.12, 230.45, 233.97, 316.08;

IR (thin ﬁlm on NaCl): 2007 (m), 1892 (s), 1833 (s),

1707 (m), 1351 (m), 1220 (w), 698 (w), 671 (w), 607 (w)

(

and reﬁnement of the structure in P1; the monoclinic

and orthorhomibic space groups were uniquely deter-

mined from the systematic absences. No absorption

corrections were performed as the transmission ratio

was less than 1.15 in all cases. All non-hydrogen atoms

208

T.S. Powers et al. / Journal of Organometallic Chemistry 617–618 (2001) 182–208

[11] The barrier to rotation about the carbene carbonꢀnitrogen bond

in alkyl amino carbene complexes of the type 5 is normally quite

high (]25 Kcal mole⁻¹) and thus both degrees of freedom

present in alkoxy complex is absent in amino complexes. How-

ever, this barrier to rotation may not be present in reactive

intermediates formed in the reactions of alkyl amino carbene

complexes [5c].

were anisotropically reﬁned except for C(1) to C(5) in

107 to conserve data. Hydrogens atoms were treated as

idealized contributions. Various versions of ^SHELXTL

4

and 5 were used in the solution and reﬁnement (G.

Sheldrick, Siemens XRD, Madison, WI).

[12] For previous work on the synthetic utility of these complexes,

see Ref. [3] and: (a) T.S. Powers, Y. Shi, K.J. Wilson, W.D.

Wulff, J. Org. Chem. 59 (1994) 6882. (b) Y. Shi, W.D. Wulff, J.

Org. Chem. 59 (1994) 5122. (c) Y. Shi, W.D. Wulff, G.P.A. Yap,

A.L. Rheingold, J. Chem. Soc. Chem. Commun. (1996) 2601. (d)

T.S. Powers, W. Jiang, J. Su, W.D. Wulff, B.E. Waltermire, A.L.

Rheingold, J. Am. Chem. Soc. 119 (1997) 6438. (e) M.P. Parisi,

A. Solo, W.D. Wulff, I. Guzei, A.L. Rheingold, Organometallics

(1998) 17, 3696.

[13] J.A. Connor, E.M. Jones, J. Chem. Soc. A (1971) 3368.

[14] J. Montgomery, G.M. Wieber, L.S. Hegedus, J. Am. Chem. Soc.

112 (1990) 6255.

[15] It should be noted that the terms Z and E used here to describe

the stereochemistry of the two rotamers about the carbene

carbonꢀnitrogen bond are reversed from the usage employed by

Fischer for this same purpose. (a) E. Moser, E.O. Fischer, J.

Organomet. Chem. 16 (1969) 275. (b) E.O. Fischer, M. Leupold,

Chem. Ber. 105 (1972) 599.

6. Supplementary material

Crystallographic data for the atomic coordinates,

thermal parameters, bond distances and bond angles

has been deposited with the Cambridge Crystallo-

graphic Data Centre, CCDC. Copies of this informa-

tion may be obtained free of charge from: The

Director, CCDC, 12 Union Road, Cambridge, CB2

1EZ, UK (Fax: +44-1223-336033; e-mail: deposit@

ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).

Acknowledgements

[16] E. Moser, E.O. Fischer, J. Organomet. Chem. 13 (1968) 387.

[17] (a) F.R. Kreissl, E.O. Fischer, C.G. Kreiter, K. Weiss, Angew.

Chem. Int. Ed. Engl. 12 (1973) 563. (b) F.R. Kreissl, E.O.

Fischer, Chem. Ber. 107 (1974) 183.

[18] (a) E.O. Fischer, F.R. Kreissl, J. Organomet. Chem. 35 (1972)

C47. (b) E.O. Fischer, H.J. Kalder, J. Organomet. Chem. 131

(1977) 57.

[19] (a) W.J. Close, J. Org. Chem. 15 (1950) 1131. (b) G. Cardillo, A.

D’Amico, M. Orena, S. Sandri, J. Org. Chem. 53 (1988) 2354. (c)

S.E. Drewes, D.G.S. Malissar, G.H.P. Roos, Chem. Ber. 126

(1993) 2663.

This work was supported by the National Institutes

of Health (PHS-GM 33589). This was performed in the

Chemistry Department at the University of Chicago.

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