Synthesis of chromium aminocarbene complexes of diterpenoids

Journal of Organometallic Chemistry 626 (2001) 199–220

www.elsevier.nl/locate/jorganchem

Paul D. Woodgate *, Hamish S. Sutherland, Clifton E.F. Rickard

Department of Chemistry, The Uni6ersity of Auckland, Pri6ate Bag 92019, Auckland, New Zealand

Received 4 January 2001; received in revised form 19 January 2001

Abstract

Chromium aminocarbene complexes of podocarpane diterpenoids have been synthesised in good to excellent yields, either by

aminolysis of the corresponding alkoxycarbene, or by treatment of the morpholino amide with disodium pentacarbonylchromium

Keywords: Chromium; Aminocarbene; Diterpenoid

1. Introduction

of 13- and 14-phenyldienyl products in 90% yield. With

the aim of minimising the number of products [7] we

attempted to complex a 7b-OR diterpenoid (R=H,

TBDMS) using the Sweigart procedure, the expectation

being that a benzylic hydroxy or alkoxy group would

direct the Mn(CO)₃moiety to the b face of the arene,

by analogy with the Cr(CO)₃work. In the event, the

only identiﬁable product was the non-complexed sty-

rene analogue resulting from elimination promoted by

either AgBF₄or a cationic manganese species. The use

of Mn(CO)₃(h⁶-naphthalene)⁺in an attempt to transfer

the Mn(CO)⁺₃moiety to a 7b-OCH₂OMe podocarpic

acid derivative gave only a trace of the desired (h⁶-

diterpenoidarene)tricarbonylmanganese complex. We

have synthesised the analogous cationic (h⁶-diter-

The use of organotransition metal mediated chem-

istry in the transformation of podocarpic acid (1; R¹=

R²=H) derivatives in earlier work by us has been

directed generally towards the modiﬁcation of the aro-

matic ring-C by the construction of a fused pentacyclic

ring (D ring), leading to molecules possessing a

steroidal skeleton 2 (Scheme 1).

During the course of this work we have investigated

nucleophile

addition

to

(h⁶-diterpenoidarene)-

tricarbonylchromium complexes [1–5] (generally lim-

ited to carbanions derived from carbon acids with a

pK_a\22). Sweigart et al. [6] have prepared the

analogous cationic (h⁶-arene)tricarbonylmanganese

diterpenoid complexes as a 1.1:1 mixture of a and b

diastereoisomers. Reaction of these complexes with

phenylmagnesium bromide gave an inseparable mixture

penoidarene)(cyclopentadienyl)ruthenium

complexes

(a/b, 5:1) in good yield using the transfer reagent

(MeCN)₃RuCp⁺[8]. However, nucleophile addition to

simple (h⁶-arene)RuCp⁺complexes is limited [9] to

either hydride or phenyllithium, although the related

h⁶-arene (pyrazolylborate)ruthenium [10] complexes

will also react with hydroxide and cyanide to give

h⁵-cyclopentadienyl complexes [11]. Since a much wider

range of nucleophiles [12–17] undergo addition to

cationic tricarbonyl(h⁵-pentadienyl)iron complexes,

preparation of some diterpenoid congeners was also

studied [18]. The yields of the b 8(9),10(11) and a

8(14),12(13) h⁴-dienyliron intermediates, and of the

derived cationic h⁵-cyclopentadienyl complex(es), were

too low, however, to warrant investigation of reactions

of the latter.

Scheme 1.

* Corresponding author. Tel.: +64-9-3737599 ext. 8262; fax: +64-

9-3737422.

E-mail address: p.woodgate@auckland.ac.nz (P.D. Woodgate).

PII: S0022-328X(01)00700-8

200

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

Scheme 2.

In contrast to exploration of the above options for

1954 cm⁻¹in the IR spectrum (hexanes). A broad

singlet at 4.16 ppm in the ¹H-NMR spectrum was

assigned to the carbene methoxy group, and the singlets

at 6.42 and 6.74 ppm were assigned to H(14) and

H(11), respectively [19]. Resonances at 216.1 and 225.3

ppm in the ¹³C-NMR spectrum were characteristic of

the cis- and trans-carbonyl ligands, respectively, and

the signal due to the carbene carbon was observed at

355.4 ppm. The NMR spectra of the minor product 8

conﬁrmed the presence of the ligated 12-methoxy group

(l_H(OMe)4.85, l_C(OMe)64.5 ppm: l_CCr333.8; l_CO232.0,

231.3 and 213.9 ppm). For a related series of com-

pounds, it has been shown that the lower the carbonyl

force constant, the longer the CꢀO bond and the higher

the l_CO[22]. The X-ray structural data [23] for the

benzenoid analogue, pentacarbonyl[(methoxy)(h-2-

methoxyphenyl)carbene]chromium, indicates that the

CO ligand which is trans to the 2-methoxy group has

the longest CꢀO bond. Consequently, it has the car-

bonyl signal at lowest ﬁeld in the ¹³C-NMR spectrum,

followed (decreasing l) by the CO ligand which is trans

to the carbene carbon and then the carbonyls which are

trans to each other. Therefore, the signal at 232.0 ppm

in the ¹³C-NMR spectrum of the diterpenoid carbene 8

was assigned to the carbonyl ligand trans to the O-

donor, the signal at 231.3 ppm was assigned to the

carbonyl ligand trans to the carbene, and the signal at

213.9 ppm was assigned to the carbonyl ligands which

are trans to each other. High-resolution mass spec-

troscopy gave the molecular ion at 494.1408

(C₂₅H₃₀CrO₇), and the base peak at m/z 382 corre-

sponded to the loss of four carbonyl ligands.

attaching carbon nucleophiles to h⁶-arene transition

metal complexes, chromium alkoxycarbenes offer a dif-

ferent mode of preparation and reaction. Initial investi-

gations showed that reaction of phenylacetylene with

the pentacarbonylchromium ethoxycarbene complex of

the diterpenoid 3 led to the ring-C aromatic steroidal

analogues 4/5 (Scheme 2) [19]. Since our initial study,

greater understanding has been accumulated with re-

gard to potential control of the benzannulation versus

cyclopentaannulation pathways [20] during reaction of

an alkyne with a chromium carbene complex. In partic-

ular, chromium aminocarbenes offer the opportunity

for the cyclopentaannulation route to dominate. These

ﬁndings provided the impetus to extend our earlier

work by investigating the preparation of chromium

aminocarbenes derived from podocarpic acid, and their

reactions with alkenes and alkynes, as a route to ring-C

aromatic steroidal analogues.

2. Discussion

Preparation of the diterpenoid aminocarbenes re-

quired the synthesis of the corresponding precursor

alkoxycarbenes. In order to avoid reaction of a 19-car-

bonyl group with BuLi, the diterpenoid alkoxycarbene

chosen as the synthesis target was the 19-ether, pen-

tacarbonyl[methoxy(13 - (12,19 - dimethoxypodocarpa-

8,11,13-triene))carbene]chromium (7) (Scheme 3). The

aryl bromide 6 [21] underwent metal–halogen exchange

with BuLi in THF at −78°C; after 3 min the solution

of the 13-lithioarene was transferred into a slurry of

Cr(CO)₆(1.05 equivalents) in diethyl ether at 0°C. After

3 h at room temperature the resulting lithio acylate was

treated at 0°C with methyl triﬂate. This sequence gave

7

(76%) and tetracarbonyl [(methoxy)(13-(12,19-

dimethoxypodocarpa-8,11,13-triene-C¹³,O¹²))carbene]-

chromium (8) (2%; a higher percentage was isolated

from some runs due to the variable length of time

needed for removal of solvent under vacuum). The

pentacarbonyl carbene complex 7 showed a weak

molecular ion in the mass spectrum at m/z 522.1349

(C₂₆H₃₀CrO₈), and the base peak at m/z 382 corre-

sponded to expulsion of all ﬁve carbonyl ligands. Peaks

due to carbonyl ligands occurred at 2063, 1989 and

Scheme 3.

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

201

Scheme 4.

Small amounts (B5%) of 12,19-dimethoxypodo-

carpa-8,11,13-triene were also isolated, due to deproto-

nation of the solvent (THF [24] or diethyl ether) by the

intermediate 13-lithio diterpenoid. The use of THF as

the solvent in the metal–halogen exchange, and of

diethyl ether for reaction of the ensuing aryllithium

with Cr(CO)₆, was crucial to the success of the diter-

penoid alkoxycarbene synthesis. The insolubility of the

13-bromo diterpenoid 6 in diethyl ether at −78°C

precluded use of the latter as the solvent for the metal–

halogen exchange reaction. When THF was used as the

solvent for both the metal–bromide exchange and the

subsequent reactions with Cr(CO)₆and methyl triﬂate,

a polymer ([CH₂(CH₂)₂CH₂O]_n; l_H1.62, 3.41 ppm)

formed which was impossible to separate from the

desired carbene complex.

In order to convert the diterpenoid derivatives even-

tually into the more common (e.g. 3-oxo) steroidal

analogues, modiﬁcation of the diterpenoid A-ring into

an exocyclic 4(18)-alkene was desirable, since further

functionalisation could be achieved using the exo meth-

ylene group as a handle. The alkoxycarbene 9 was

synthesised (Scheme 4) in four steps from 13-bromo-12-

methoxypodocarpa-8,11,13-trien-19-oate (10). Treat-

ment of the acid chloride 11 with the sodium salt of

1-hydroxy-2-pyridinethione gave the sulﬁde 12 in quan-

titative yield; an X-ray crystallographic analysis (Fig. 1)

showed that inversion had occurred at C(4) [25]. Since

formation of 12 was 100% stereoselective it is suggested

that the pyridyl ester derived from 11 reacts via a

near-concerted pathway, involving attack of thione sul-

fur at the least hindered a face of the diterpenoid

concomitant with decarboxylation. The sulﬁde was oxi-

dised to the sulfoxide with m-CPBA, and subsequent

thermally promoted cycloelimination gave the desired

4(18)-alkene 13. Formation of the carbene complex 9

was achieved (72%) using the methodology developed

for 7; small amounts of the tetracarbonyl carbene com-

plex 14 were also isolated.

Four routes have been devised for the synthesis of

chromium aminocarbenes [26,27]. Aminolysis of the

corresponding alkoxycarbene is restricted to primary

amines or non-hindered secondary amines. Sterically

demanding amine groups can be introduced by aminol-

ysis of acyloxycarbenes, which are highly reactive spe-

cies available from the corresponding tetra-

alkylammonium acylate and acetyl bromide [28].

Aminocarbene complexes having hydrogen on the car-

bene carbon cannot be prepared by aminolysis of either

an alkoxycarbene or an acyloxycarbene, since the corre-

sponding formyl complexes are strong hydride donors

which cannot be O-alkylated or O-acylated. Such

aminocarbene complexes can, however, be synthesised

by reacting Na₂Cr(CO)₅with (chloromethylene)-

dialkylammonium chlorides [29,30]. A better route in-

volves reaction of alkyl and aryl N,N-dialkylamides,

Fig. 1. The atomic arrangement in 12.

202

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

while the signal due to the carbene carbon occurred at

270.2 ppm.

Reaction of pentacarbonyl[(methoxy)(2-methoxy-

phenyl)carbene]chromium (15) with ammonia in THF at

room temperature gave pentacarbonyl[(dihydroamino)-

(2-methoxyphenyl)carbene]chromium (17) (99%). As-

signment of the signals due to the NH hydrogens in the

¹H-NMR spectrum of 17 (Z-NH, 8.46; E-NH, 9.01 ppm)

was based upon the positions of the signals due to the

E and Z NH protons in the NMR spectrum of the

aminocarbene (18) (92%; E/Z, 2:1), prepared similarly

from reaction of the methoxycarbene 15 with methyl-

amine. In the ¹H-NMR spectrum of 18, the methyl

groups appeared as doublets at 2.94 (J=4.8 Hz) and 3.73

ppm (J=5 Hz) and were assigned to NCH₃(E) and

NCH₃(Z) on the basis of their respective Dl values. The

E-NH signal at 9.12 was broad, as was the Z-NH signal

at 8.78 ppm [35]. The E and Z isomers also showed

different chemical shifts for the aromatic protons, the

relative intensity of each signal being used to aid assign-

ments. Different chemical shifts [except for C(2)] were

also observed for each isomer in the ¹³C-NMR spectrum.

Aminolysis of 15 with dimethylamine gave the

(dimethylamino)carbene 19 (92%) [31]. The singlets at

3.06 and 3.97 ppm were assigned to NCH₃(E) and

NCH₃(Z), respectively, by comparison with those from

the carbene 18, as were the N-methyl groups in the

¹³C-NMR spectrum [NCH₃(E), 45.3; CH₃(Z), 50.9 ppm].

Reaction of pyrrolidine with 15 gave pentacarbonyl[(2-

Scheme 5.

lactams or tertiary formamides with Na₂Cr(CO)₅[31,32]

or K₂Cr(CO)₅[33] to give a dianionic intermediate which

undergoes O-silylation with chlorotrimethylsilane to give

the monoanionic intermediate. Alumina-promoted elim-

ination of trimethylsilyloxide then affords the aminocar-

bene in good to excellent yields.

In the present work, a number of benzenoid aminocar-

bene model compounds were synthesised in order to

allow assignments derived from the spectroscopic data of

the simple compounds to be applied to the diterpenoid

aminocarbenes.

Aminolysis

of

pentacarbonyl-

(15)

[(methoxy)(2-methoxyphenyl)carbene]chromium

with aziridine gave pentacarbonyl[(aziridinyl)(2-

methoxyphenyl)carbene]chromium (16) (86%) (Scheme

5). The molecular ion at m/z 352.9968 (C₁₅H₁₁CrNO₆) in

the mass spectrum underwent sequential loss of ﬁve

carbonyl ligands and then of ethene from the aziridine

group to give an odd electron fragment ion at m/z 185.

A NOESY spectrum of the aziridinyl carbene showed a

weak nOe between a doublet at 6.91 ppm (J=8.3 Hz)

and the methoxy group (3.78 ppm), and therefore the

signal at 6.91 ppm was assigned to H(3). A ddd splitting

pattern at 7.24 ppm (J=8.3, 7.5, 1.6 Hz) was assigned

to H(4), a triplet at 6.99 ppm (J=7.5 Hz) to H(5) and

the doublet of doublets at 6.83 ppm (J=7.5, 1.6 Hz) to

H(6). Strong overlap of the nitrogen p-orbital with the

metal p-orbitals results in signiﬁcant carbene carbon–ni-

trogen double bond character. That is, restricted rotation

around the CꢁN bond results in E and Z aziridinyl

methylene groups. For an N,N-diethylaminocarbene

derivative the solvent induced chemical shift difference

[Dl(CHCl₃-dꢂC₆H₆-d₆) 1.00] for an E-CH₂group is

larger than for a Z-CH₂group (Dl 0.54) [34]. The triplet

at l_H2.58 in the spectrum of the aziridinyl complex 16

in C₆H₆-d₆was therefore assigned to NCH₂(E)

[Dl(CHCl₃-dꢂC₆H₆-d₆)=1.20] while that at 3.24 ppm

was assigned to NCH₂(Z) (Dl 1.04). A ¹³C–¹H correla-

tion spectrum then showed that the signal at l_C27.6

represented CH₂(Z), while that at 28.4 ppm represented

CH₂(E). The ¹³C-NMR spectrum included signals for the

cis CO ligands at 217.5 and the trans CO ligand at 224.0,

methoxyphenyl)(pyrrolidinyl)carbene]chromium

(20)

(96%). The COSY NMR spectrum showed that the

signals due to CH₂CH₂N at 1.98 ppm correlated with

those due to NCH₂at 3.19 and 3.35 ppm, while those due

to CH₂CH₂N at 2.19 ppm correlated with those due to

1

NCH₂at 4.24 and 4.30 ppm. Signals in the H-NMR

spectrum were assigned to either the E or Z isomer on

the basis of Dl values, and assignments of signals to

either axial or equatorial hydrogens were made by

comparison with those in the morpholino aminocarbene

complex (see later). The ¹³C-NMR data was assigned

from ¹³C–¹H correlation spectra.

Reaction of morpholine with the methoxycarbene 15

did not afford the expected aminocarbene, but gave

(morpholino)pentacarbonylchromium (21) (37%) [36].

Repeating the reaction using 20 molar equivalents of

morpholine again gave (21) (28%). Although the parent

pentacarbonyl[(morpholino)(phenylcarbene]chromium

(22) has been synthesised (76%) from treatment of the

corresponding phenylmethoxy carbene with an excess of

morpholine [37], the increase in steric hindrance due to

the presence of an ortho methoxy group in (15) is

apparently enough to inhibit the desired substitution.

The failure of morpholine to give an aminocarbene

complex contrasts with the successful reaction with

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

203

pyrrolidine, and emphasizes that aminolysis of the

methoxycarbene 15 is highly dependent on the steric

bulk of the amine.

naphthalenide and Cr(CO)₆[32,39], followed by O-sily-

lation with chlorotrimethylsilane and then alumina-me-

diated elimination, gave 22 (48%). Mass spectroscopy

(DEI) gave the molecular ion at m/z 367.0148

(C₁₆H₁₃CrNO₆) and the base peak at m/z 227, corre-

sponding to the sequential loss of ﬁve carbon monoxide

ligands. A weak peak at m/z 350 analysed correctly for

C₂₂H₂₆N₂O₂and is due to the dimerisation of two

metal-free carbene units. Pleasingly, reaction of (N-

morpholino)2-methoxyphenylamide (24) (from 2-

methoxybenzoyl chloride and SOCl₂, then morpholine)

with Na₂Cr(CO)₅, followed by O-silylation and silylox-

ide elimination, gave pentacarbonyl[(morpholino)(2-

methoxyphenyl)carbene]chromium (25) (79%). The

molecular ion occurred at m/z 397.0240 (C₁₇H₁₅CrNO₇)

in the mass spectrum, and the carbene ‘‘dimer’’ was

detected as a weak peak at m/z 410.2198 (C₂₄H₃₀N₂O₄).

The COSY and ¹³C–¹H-NMR spectra of 25 in CHCl₃-d

led to the assignments in Table 1. Solvent induced

chemical shifts were studied in an attempt to determine

the E/Z assignments for 25, but no reliable information

could be obtained as the signals due to the axial and

equatorial hydrogens on a particular carbon did not

show the same chemical shift differences on changing

the solvent from CHCl₃-d to C₆H₆-d₆. However, Dl

values could be determined for the phenyl complex 22

(Table 2; assignments were conﬁrmed by selective de-

coupling experiments), and this information was then

applied to the chemical shifts for the 2-methoxyphenyl

derivative 25. Since the distinction between the CH₂

signals as either axial or equatorial for the aminocar-

bene derivative 25 could not be made from the NMR

spectra, tentative assignments were made by compari-

son with those for a related trans-2,6-dimethylmor-

pholino aminocarbene [40].

The

non-aromatic

carbene,

pentacarbonyl-

[(methyl)(morpholino)carbene]chromium has been syn-

thesised (78%) by treatment of N-acetylmorpholine

with Na₂Cr(CO)₅, followed by O-silylation then elimi-

nation of trimethylsiloxide [33]. In the present work,

pentacarbonyl[(morpholino)(phenyl)carbene]chromium

(22) was chosen as a model system to explore this route.

Treatment of N-(morpholino)phenylamide [38] (23) in

THF with Na₂Cr(CO)₅freshly prepared from sodium

Table 1

CꢂH correlations for (morpholino)(2-methoxyphenyl)carbene) 25

l_H(CHCl₃-d, ppm)

l_C(CHCl₃-d, ppm)

Assignment

3.42–3.57

3.57–3.68

4.02

4.09

4.43

55.1

67.2

67.9

60.1

NCH_2(E)

OCH_2(E)

OCH_(Z)axial

OCH_{(Z)equatorial}

NCH_(Z)axial

NCH_{(Z)equatorial}

4.71

Table 2

Solvent induced shifts for (morpholino)(phenyl)carbene 22

With the practical experience and spectroscopic in-

formation garnered from the model aminocarbenes in

hand, syntheses of the diterpenoid analogues were in-

vestigated, following the particular method developed

for the corresponding benzenoid aminocarbene. Thus,

treatment of the methoxy carbene 7 with ammonia in

THF gave pentacarbonyl[(dihydroamino)(13-(12,19-

dimethoxypodocarpa-8,11,13-triene)carbene]chromium

l

Dl

Assignment

(CHCl₃-d, ppm) (CHCl₃-d, ppm) (CHCl₃-d–C₆H₆-d₆)

4.58

4.08

3.62

3.50

3.93

3.40

2.72

2.56

0.65

0.68

0.90

0.94

NCH₂(Z)

OCH₂(Z)

OCH₂(E)

NCH₂(E)

1

(26) (89%) (Scheme 6). Broad signals in the H-NMR

spectrum at 8.65 and 8.94 ppm were assigned to NH(Z)

and NH(E), respectively. Two singlets at 6.74 [H(14)]

and 7.77 ppm [H(11)] were observed in the aromatic

region. Reaction of methylamine with 7 gave pentacar-

bonyl[(methylamino)(13 - (12,19 - dimethoxypodocarpa-

1

8,11,13-triene) carbenechromium (27) (82%). In the H-

NMR spectrum (CHCl₃-d, 298 K, 400 MHz) the pairs

of doublets (J=4.6 Hz; two rotamers) at 2.93 and 2.94

were assigned to N-methyl (E) and the doublet at 3.69

ppm (J=5.0 Hz) was assigned to N-methyl (Z) (E/

Z=3:2). There were three singlets for H(14), each

isomer as well as each rotamer of the E isomer (Scheme

Scheme 6.

204

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

[CH_eq(Z)]. COSY, ¹³C–¹H and long range ¹³C–¹H-

NMR spectra conﬁrmed that the relative assignments

for H(11) and H(14) in the diterpenoid alkoxycarbene 3

[19] are also applicable to the aminocarbenes.

In contrast to the successful aminolyses describe

above, the morpholino carbene 31 could not be synthe-

sised from the methoxy carbene, but was available from

an acyloxycarbene (Scheme 8). Thus, lithium–halogen

exchange (t-BuLi, −100°C) of the 13-bromoarene 6

followed by reaction of the aryl carbanion with

Cr(CO)₆gave a lithium acylate which was converted

into the tetramethylammonium acylate. Reaction of

this salt with acetyl bromide gave the acetyloxycarbene,

treatment of which with morpholine afforded the mor-

pholino carbene 31 (37%). A better route to 31 pro-

ceeded via N-morpholino-12,19-dimethoxypodocarpa-

8,11,13-triene-13-carboxamide (32), prepared (90%)

from the 13-lithio diterpenoid and 4-morpholinocar-

bamoyl chloride (Scheme 9). Addition of the amide 32

to a solution of disodium pentacarbonylchromium, fol-

lowed by O-silylation and alumina-mediated silyloxide

Scheme 7.

Scheme 8.

7) (atropisomers are also possible) having a distinct

chemical shift; the E/Z assignments for H(14) were

made by comparison with the integral areas of the

signals due to NH(E) and NH(Z) (9.08 and 8.75 ppm,

respectively). The isomer/rotamer mixture was also in-

dicated by the ¹³C-NMR spectrum, in which there were

three signals due to a carbene carbon (268.6, 280.7 and

281.4) and two [223.6, (CꢀO_(E)); 224.2 ppm, (CꢀO_(Z))]

for a trans carbonyl ligand.

Reaction of dimethylamine with 7 in THF at room

temperature gave pentacarbonyl[(dimethylamino)(13-

(12,19 - dimethoxypodocarpa - 8,11,13 - triene)carbene]-

chromium (28) (89%). The carbene moiety was evident

elimination

gave

pentacarbonyl[(morpholino)(13-

(12,19 - dimethoxypodocarpa - 8,11,13 - triene)carbene]-

chromium (31) (76%) (M⁺577.1803, C₂₉H₃₅CrNO₈).

The ¹³C-NMR spectrum showed peaks at 217.3

(CꢀO_cis), 224.0 (CꢀO_trans) and 271.6 ppm (C_carbene) while

the infrared spectrum showed absorptions due to car-

bonyl ligands at 2052, 1971 and 1926 cm⁻¹. As with

the pyrrolidino carbene, high concentrations of the

morpholino carbene in CHCl₃-d caused the signal due

to H(14) to double, due to the detection of rotamers.

Increasing the temperature (CHCl₃-d or C₆H₆-d₆) re-

sulted in broadening of the NMR signals due to partial

decomposition of the carbene, and therefore the rota-

tional energy barriers could not be measured. A single

crystal of the aminocarbene 31 suitable for X-ray dif-

fraction analysis (Fig. 2) was grown from a solution in

hexanes at 0°C. The morpholino substituent is a good

1

by H-NMR signals due to the N-methyl protons as

singlets at 3.06 [NCH₃(E)] and 3.94 ppm [NCH₃(Z)].

Pentacarbonyl[(aziridinyl)(13 - (12,19 - dimethoxypodo-

carpa-8,11,13-triene))carbene]chromium (29) (81%)

(M⁺533.1500, C₂₇H₃₁CrNO₇) was synthesised by

aminolysis of the alkoxycarbene 10 with aziridine. The

presence of an aziridinyl group was conﬁrmed by the

doublets (J=5.5 Hz) at 2.59 [NCH₂(E)] and 3.20 ppm

,

p-donor, and therefore the NꢂC_carbenebond [1.315(4) A]

1

[NCH₂(Z)] in the H-NMR spectrum, a COSY spec-

shows signiﬁcant double bond character. Increasing the

p-donor capacity of the carbene heteroatom decreases

the amount of back-bonding, and consequently the

trum showing that these doublets were coupled only

with each other. Pentacarbonyl[(pyrrolidinyl)(13-(12,19-

dimethoxypodocarpa-8,11,13-triene))carbene]chromium

,

CrꢂC_aminocarbenebond [2.111(3) A] is longer than the

(30) (M⁺561.1833, C₂₉H₃₅CrNO₇) was prepared (91%)

CrꢂC_{alkoxycarbene}bond (1.97–2.05 A) [23]. The cis CO

,

similarly. The pyrrolidinyl N-methylene protons were

observed as doublets of doublets of doublets at 3.21

[CH_ax(E)], 3.37 [CH_eq(E)], 4.20 [CH_ax(Z)], and 4.26 ppm

bonds are longer CrꢂC [1.884(5)–1.891(5) A] than the

,

trans CO bond [1.857(4) A]; the carbene is a poorer

p-acceptor than a carbonyl ligand, and therefore the

Scheme 9.

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

205

Fig. 2. The atomic arrangement in 31.

trans CO can accept more of the p-electron density

from the chromium relative to the cis CO ligands,

which have to compete with each other.

oxy-19-norpodocarpa-4(18),8,11,13-tetraene))carbene]-

chromium (38) could not be synthesised from treatment

of 9 with morpholine, it was available in good yield

(77%) by adding the amide 39 to a solution of

Na₂Cr(CO)₅at −78°C, followed by O-silylation of the

dianion and then alumina-mediated elimination of

trimethylsilyloxide (Scheme 11). ¹H-NMR spectra

showed that 38 existed as a mixture (1:1) of rotamers

(298 K, 400 MHz), signals due to H(14) being observed

at 6.35 and 6.40 ppm.

Condensation of ammonia gas into a solution of

the alkoxycarbene

9 gave pentacarbonyl[(dihydro-

amino)(13-(12-methoxy-19-norpodocarpa-4(18),8,11,13-

tetraene))carbene]chromium (33) (Scheme 10). Recrys-

tallisation of 33 from hexanes gave yellow ﬂaky crystals

suitable for X-ray crystallographic analysis (Fig. 3).

,

The CrꢂC_carbene[2.105(4) A] and NꢂC_carbene[1.302(5) A]

bond lengths were similar to those of the morpholino

analogue 31.

In order to ascertain whether steric or electronic

effects were responsible for the variation in yields of

insertion products (to be published), trans-2,6-

dimethylmorpholino carbene complexes (Scheme 12)

were synthesised to compare with the yields from the

morpholino complexes. 12-Methoxy-19-norpodocarpa-

4(18),8,11,13-tetraen-13-oic acid (41) was prepared by

metal–halogen exchange on the 13-bromo diterpenoid

13 followed by quenching of the lithioarene with solid

carbon dioxide. Reaction of racemic trans-2,6-

dimethylmorpholine [40] with the derived acid chloride

41 gave 12-methoxy-N-(trans-2,6-dimethylmorpholino)-

19 - norpodocarpa - 4(18),8,11,13 - tetraene - 13 - carboxa-

Similar reaction of 9 with methylamine gave pen-

tacarbonyl[(methylamino)(13-(12-methoxy-19-norpodo-

carpa-4(18),8,11,13-tetraene)carbene]chromium

(34)

(92%), as a mixture (5:1) of E and Z isomers (cf.

Scheme 7). The E isomer existed as a pair of rotamers

at 298 K (¹H-NMR, 400 MHz). Both E and Z isomers

had different chemical shifts for a particular hydrogen

or carbon. For example, signals due to the carbene

carbon were observed at 280.7 (C_carbene(Z)) and 281.3

ppm (C_carbene(E)). The signals due to the N-methyl hy-

drogens were observed as doublets at 2.95 (E isomer,

J=4.9 Hz) and 3.70 ppm (Z isomer, J=5.1 Hz), and

broad signals at 8.77 and 9.10 ppm were assigned to

1

mide (43). Signals in the H-NMR spectrum (400 MHz)

at 6.72, 6.79, 6.80 and 6.84 ppm were assigned to

H(11), indicating that the amide was a mixture of four

rotamers (two from each diastereoisomer) at 298 K.

Addition of the amide 43 to Na₂Cr(CO)₅in THF at

−78°C followed by quenching with chlorotrimethylsi-

NH_(Z)and NH_(E), respectively. Surprisingly, the

analogous dimethylaminocarbene 35 was relatively un-

stable. Signals in the ¹³C-NMR spectrum at 45.2(5) and

45.3 ppm were assigned to NCH_3(Z)and that at 50.8

ppm was assigned to NCH_3(E). Reaction of aziridine

with the alkoxycarbene

9

gave pentacarbonyl-

[(aziridinyl)(13-(12-methoxy-19-norpodocarpa-4(18),8,

11,13-tetraene))carbene]-chromium (36). Signals due to

the aziridinyl group appeared at 28.7 (NCH_2(Z)) and

29.1(5) ppm (NCH_2(E)) in the ¹³C-NMR spectrum. Pen-

tacarbonyl[(pyrrolidinyl)(13-(12-methoxy-19-norpodo-

carpa-4(18),8,11,13-tetraene))carbene]chromium

(37)

(89%) was shown to be a mixture (7:3) of rotamers by

¹H-NMR analysis (298 K, 400 MHz). Singlets due to

H(14) at 6.33 and 6.37 ppm were assigned to the major

and minor rotamers, respectively.

Although pentacarbonyl[(morpholino)(13-(12-meth-

Scheme 10.

206

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

Fig. 3. The atomic arrangement in 33.

Scheme 11.

Scheme 12.

lane and alumina-mediated silyloxide elimination gave

pentacarbonyl[(trans-2,6-dimethylmorpholino)(13-(12-

methoxy - 19 - norpodocarpa - 4(18),8,11,13 - tetraene)-

carbene] chromium (40) (57%) (Scheme 12). The NMR

spectra of 40 were complicated, three carbene carbon

signals being observed in the ¹³C spectrum, at 272.1,

272.2 and 272.3 ppm. The molecular ion was observed

at m/z 559.1668 (C₂₉H₃₃CrNO₇) in the mass spectrum,

the base peak at m/z 419 corresponding to the loss of

ﬁve carbonyl ligands from the molecular ion. The 19-

methyl ether analogue, pentacarbonyl[(trans-2,6-

dimethylmorpholino)(13 - (12,19 - dimethoxypodocarpa-

8,11,13-triene))carbene]chromium (44), was synthesised

(645464744) by the route developed for the

4(18)-alkene aminocarbene (40). Again, the NMR spec-

tra were complicated by the presence of rotamers.

Thus, four signals due to the carbene carbon were

observed in the ¹³C-NMR spectrum (272.0, 272.2, 273.9

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

207

and 274.1 ppm), and four singlets assigned to H(14)

2.2. Summary

were observed in the ¹H-NMR spectrum (6.22, 6.25,

6.32 and 6.35 ppm).

We have shown that aminocarbene complexes of

diterpenoids can be synthesised in excellent yield either

by the aminolysis of the corresponding alkoxycarbene

or by treatment of the morpholino amide with dis-

odium pentacarbonylchromium and subsequent elimi-

nation of silyloxide. Reactions of these complexes with

alkenes and alkynes will be reported in due course.

2.1. X-ray crystal structures of 12, 31, and 33

Data were collected on a Siemens SMART area

detector diffractometer using 0.3° frames and proﬁle

ﬁtting. Lorentz, polarisation and absorption corrections

[41] were applied and equivalent reﬂections averaged to

give 4554 unique data for 12, 5078 unique data for 31,

and 4631 unique data for 33. Unit cell parameters were

obtained by least-squares ﬁt to all data with I\10|(I).

The structures were solved by direct methods [42] and

reﬁned by full-matrix least-squares on F²[43]. Hydro-

gen atoms were placed geometrically and reﬁned with a

riding model, including free rotation for methyl groups,

with thermal parameter 20% (50% for methyl groups)

greater than U_isoof the carrier atom. All non-hydrogen

atoms were reﬁned with anisotropic thermal parame-

ters. Reﬁnement converged to R₁(observed data)

0.0204 for 12, 0.0467 for 31, and 0.0514 for 33. Crystal

data and reﬁnement parameters are given in Table 3

and the structures, including the absolute conﬁguration,

are shown in Figs. 1–3.

3. Experimental

3.1. Pentacarbonyl[(methoxy)(13-(12,19-

dimethoxypodocarpa-8,11,13-triene))carbene]-chromium

(7)

Butyllithium (1.30 ml, 2.09 mol l⁻¹) was added to a

solution

of

13-bromo-12,19-dimethoxypodocarpa-

8,11,13-triene (6) (0.996 g, 2.71 mmol) [21] in THF (7

ml) at −78°C. The solution was stirred at −78°C for

4 min and then, transferred into a slurry of Cr(CO)₆

(0.73 g, 3.31 mmol) in ether (10 ml) at 0°C. The

solution was warmed to room temperature and stirred

for 3 h. Methyl triﬂate (0.45 ml, 3.97 mmol) was added,

Table 3

X-ray data collection and processing parameters

12

31

33

Formula

Molecular weight

Temperature (K)

C

432.41

203

₂₂H₂₆BrNOS

C₂₉H₃₅CrNO₈

577.58

293

C₂₃H₂₃CrNO₆

461.42

293

,

Wavelength (A)

0.71073

Orthorhombic

P2₁2₁2₁

0.71073

Monoclinic

C2

0.71073

Orthorhombic

P2₁2₁2₁

Crystal system

Space group

,

a (A)

7.3691(1)

12.3346(2)

22.0360(1)

24.6901(8)

7.6247(2)

15.6622(5)

97.257(1)

2924.86(15)

4

1.312

1216

0.44

7.1376(1)

8.8489(2)

36.3063(3)

,

b (A)

,

c (A)

i (°)

V (A )

3

,

2002.96(5)

4

1.434

896

2.17

2293.10(6)

4

1.337

960

0.54

Z

D_calc(g cm⁻³

F(000)

)

v (mm⁻¹

)

Crystal size (mm)

2q Range (°)

Reﬂections collected

Independent reﬂections

Observed data

0.40×0.38×0.36

1.8–28.3

12481

4554 [R_int0.0185]

4325

0.25×0.20×0.06

1.3–26.0

17241

5078 [R_int0.0298]

3896

0.43×0.22×0.04

1.2–26.4

13353

4631 [R_int0.0416]

3486

A (min/max)

0.478, 0.509

ꢀw(F²_o–F²_c)²

0.017(5)

1.011

0.0204

0.0.0536

+0.21, −0.42

0.898, 0.974

ꢀw(F²_o–F²_c)²

0.02(2)

1.101

0.0467

0.802, 0.978

ꢀw(F²_o–F²_c)²

0.04(3)

1.110

0.0514

Function minimised

Absolute structure parameter

Goodness-of-ﬁt on F²

R₁(observed data)

wR₂(all data)

0.0929

0.1067

+0.21,−0.27

−3

,

Difference map (min/max) (e A

R₁=ꢀꢁꢁF_oꢁ−ꢁF_cꢁꢁ/ꢀꢁF_oꢁ

)

+0.19, −0.27

wR₂={ꢀ[w(F²_o−F²_c)²]/ꢀ[w(F_o²)²]}^1/2

Weight=1.0/[|²(F²_o)+a*P²+b*P]

P=(F²_o+2F²_c)/3

208

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

producing a red solution which was stirred for 1 h. The

solution was diluted with ether (50 ml), washed with

water, and dried. Column chromatography (hexanes/

ether, 9:1) gave: (i) pentacarbonyl[(methoxy)(13-(12,19-

dimethoxypodocarpa-8,11,13-triene))carbene]chromium

(7) (1.08 g, 76%) as a red solid, m.p. 94–96°C. Found:

3.2. 13-Bromo-12-methoxypodocarpa-8,11,13-

triene-19-carboxylic acid (10)

A solution of bromine (3.48 g, 21.8 mmol) in CH₂Cl₂

(10 ml) was added dropwise to a solution of 12-

methoxypodocarpa-8,11,13-triene-19-carboxylic

acid

M⁺522.1349. Calc. for C₂₆H₃₀CrO₈: 522.1346. u_max

[44] (6.120 g, 21.1 mmol) in dichloromethane (75 ml) at

0 °C. The solution was stirred at 0°C for 2 h, washed

with aqueous sodium dithionite, and brine, and dried.

Removal of solvent gave 13-bromo-12-methoxypodo-

carpa-8,11,13-triene-carboxylic acid (10) (7.53 g, 97%)

as ﬂaky white crystals, m.p. 227–228°C (MeOH). w_max

(log₁₀m): 402 nm (3.94). w_max(cm⁻¹): 2060 (s, CꢀO),

1

2015 (sh, CꢀO), 1943, (br, CꢀO), 1849 (s, CꢀO). H-

NMR (l ppm): 1.03 (b, H(3ax)); 1.05 (s, H(18)); 1.20 (s,

H(20)); 1.42 (dd, J=12.8, 1.6 Hz, H(5)); 1.44 (ddd,

J=13.0, 3.6 Hz, H(1ax)); 1.60–1.80 (m, H(2ax),

H(2eq), H(6ax)); 1.88 (bd, J=13.5 Hz, H(3eq)); 1.99

(bdd, J=13.4, 6.8 Hz, H(6eq)); 2.26 (bd, J=12.7 Hz,

H(1eq)); 2.77 (m, H(7ax)); 2.85 (bdd, J=16.9, 6.3 Hz,

H(7eq)); 3.25 (d, J=9.1 Hz, H(19)); 3.33 (s, 19-OMe);

3.52 (d, J=9.1 Hz, H(19)); 3.76 (s, 12-OMe); 4.16 (bs,

OMe_(carbene)); 6.42 (s, H(14)); 6.74 (s, H(11)). ¹³C-NMR

(l ppm): 19.1, C(2); 19.2, C(6); 25.6, C(20); 27.6, C(18);

30.3, C(7); 35.9, C(3); 38.0, C(10); 38.2, C(4); 39.0,

C(1); 51.1, C(5); 55.2, 12-OMe; 59.4, 19-OMe; 67.3,

OMe_(carbene); 75.9, C(19); 106.7, C(11); 121.7, C(14);

127.1, C(13), 139.0, C(8); 146.9, C(12); 151.6, C(9);

216.0, CꢀO_cis; 225.3, CꢀO_trans; 355.4, C_carbene. Mass

spectroscopy: m/z 522 [M⁺, 2], 494 (3, M−CO), 466

(2, M−2CO), 438 (2, M−3CO), 410 (21, M−4CO),

382 (100, M−5CO); and (ii) tetracarbonyl-

[(methoxy)(13 - (12,19 - dimethoxypodocarpa - 8,11,13-

triene-C¹³,O¹²))carbene]chromium (8) (0.05 g, 3%) as a

(cm⁻¹): 3300–2600 (v. br, OH), 1690 (CꢁO). H-NMR

1

(l ppm): 1.10 (ddd, J=13.6, 13.6, 4.2 Hz, H(3ax)); 1.12

(s, H(20)); 1.34 (s, H(18)); 1.40 (ddd, J=13.2, 13.2, 3.8

Hz, H(1ax)); 1.53 (dd, J=12.0, 1.4 Hz, H(5)); 1.63 (bd,

J=14.2 Hz, H(2eq)); 1.95–2.07 (m, H(2ax), H(6ax));

2.14–2.27 (m, H(1eq), H(3eq), H(6eq)); 2.70 (ddd, J=

16.5, 12.4, 6.0 Hz, H(7ax)); 2.81 (bdd, J=16.5, 5.4 Hz,

H(7eq)); 6.76 (s, H(11)); 7.20 (s, H(14)); 11.54 (b,

COOH). ¹³C-NMR (l ppm): 19.8, C(2); 20.7, C(6);

23.0, C(20); 28.6, C(18); 30.8, C(7); 37.1, C(3); 38.9,

C(10); 39.3, C(1); 43.8(5), C(4); 52.5, C(5); 56.2, 12-

OMe; 108.9, C(13); 109.2, C(11); 129.4, C(8); 133.2,

C(14); 148.4, C(9); 153.9, C(12); 184.2, C(19).

3.3. 13-Bromo-12-methoxypodocarpa-8,11,13-

trien-19-oyl chloride (11)

Thionyl chloride and 10 (0.999 g, 2.72 mmol) (0.60

ml, 8.2 mmol) were reﬂuxed in benzene (10 ml) for 18.5

h. Removal of excess thionyl chloride gave 13-bromo-

12-methoxypodocarpa-8,11,13-trien-19-oyl chloride (11)

(1.040, 99%) as a white solid. w_max(cm⁻¹): 1814 (CꢁO).

Mass spectroscopy: m/z 388 [M⁺, 27], 386 (100, M⁺),

384 (76, M⁺).

black oil. Found: M⁺

,

494.1408. Calc. for

C₂₅H₃₀CrO₇: 494.1397. w_max(cm⁻¹): 2015 (s, CꢀO),

1911 (br, CꢀO), 1843 (br, CꢀO). ¹H-NMR (l ppm):

1.00 (ddd, J=13.5, 4.2 Hz, H(3ax)); 1.04 (s, H(18));

1.18 (s, H(20)); 1.39 (dd, J=12.8, 2.0 Hz, H(5)); 1.43

(ddd, J=12.8, 3.8 Hz, H(1ax)); 1.60–1.80 (m, H(2ax),

H(2eq), H(6eq)); 1.87 (bd, J=13.6 Hz, H(3eq)); 2.01

(ddt, J=13.5, 7.4, 1.7 Hz, H(6eq)); 2.23 (bd, J=12.4

Hz, H(1eq)); 2.78 (ddd, J=17.1, 11.3, 7.2 Hz, H(7ax));

2.91 (bdd, J=17.0, 6.0 Hz, H(7eq)); 3.25 (d, J=9.1

Hz, H(19)); 3.33 (s, 19-OMe); 3.48 (d, J=9.1 Hz,

H(19)); 4.19 (s, OMe_carbene); 4.85 (s, 12-OMe); 6.85 (s,

H(14)); 7.22 (s, H(11)). ¹³C-NMR (l ppm): 19.0, C(2);

19.1, C(6); 25.3, C(20); 27.7, C(18); 30.1, C(7); 35.8,

C(3); 38.0(5), C(10); 38.7, C(4); 38.9, C(1); 50.8, C(5);

59.4, 19-OMe; 64.5, 12-OMe; 67.8; OMe_carbene; 75.9,

C(19); 106.6, C(11); 118.0, C(14); 128.9, C(13); 130.3,

3.4. 13-Bromo-12-methoxy-4h-(2%-pyridylthio)-

18-norpodocarpa-8,11,13-triene (12)

13-Bromo-12-methoxypodocarpa-8,11,13-trien-19-oyl

chloride (11) (7.791 g, 20.2 mmol) in benzene (80 ml)

was added to the sodium salt of 1-hydroxy-2-

pyridinethione (3.282 g, 22.0 mmol) and 4-N,N-

dimethylaminopyridine (0.259 g, 2.12 mmol) and the

mixture was reﬂuxed for 1.75 h under a nitrogen atmo-

sphere. The lemon coloured mixture was ﬁltered

through Celite. Column chromatography (hexanes/

C(8); 156.8, C(12); 163.8; C(9); 213.9, CꢀO_{(trans to carbonyl)}

;

231.2, CꢀO_{(trans to carbene)}; 232.1, CꢀO_{(trans to OMe)}; 333.9,

C_carbene. Mass spectroscopy: m/z 494 [M⁺, 2], 466 (2,

M−CO), 410 (17, M−3CO), 382, (100, M−4CO),

ether,

8:2)

gave

13-bromo-12-methoxy-4a-(2%-

pyridylthio)-18-norpodocarpa-8,11,13-triene (12) (8.705

g, 100%) as colourless crystals, m.p. 145–146.5°C.

26

Found: M⁺433.0894. Calc. for C₂₂H BrNOS:

81

367, (10, 382−Me ).

433.0898.

26

Found:

M⁺

431.0913.

Calc.

for

When this reaction was performed using a slurry of

Cr(CO)₆in THF instead of ether, a polymeric product

formed upon methylation with methyl triﬂate. ¹H-

NMR (l ppm): 1.62 (b, [CH₂(CH₂)₂CH₂O]_n), 3.41 (b,

[CH₂(CH₂)₂CH₂O]_n).

C₂₂H BrNOS: 431.0918. w_max(cm⁻¹): 1592 (CꢁC),

79

1569 (CꢁC), 1251 (CꢂOꢂC_anti), 774, 731, 722 (CH).

¹H-NMR (l ppm): 1.23 (s, H(20)); 1.40 (ddd, J=12.8,

4.0 Hz, H(1ax)); 1.45 (s, H(19)); 1.71–1.85 (m, H(2ax),

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

209

H(2eq), H(6ax)); 1.97 (bd, J=12.1 Hz, H(5)); 2.09 (bd,

J=13.2 Hz, H(3eq)); 2.20 (bd, J=12.0 Hz, H(1eq));

2.24 (ddd, J=13.2, 4.7 Hz, H(3ax)); 2.54 (dd, J=13.0,

7.0 Hz, H(6eq)); 2.72 (ddd, J=16.8, 11.6, 7.2 Hz,

H(7ax)); 2.83 (bdd, J=16.8, 6.2 Hz, H(7eq)); 3.86 (s,

12-OMe); 6.73 (s, H(11)); 7.09 (dd, J=7.4, 4.9 Hz,

H(4%)); 7.18 (s, H(14)); 7.40 (d, J=7.8 Hz, H(6%)); 7.52

(td, J=7.7, 1.6 Hz, H(5%)); 8.50 (dd, J=4.8, 0.8 Hz,

H(3%)). ¹³C-NMR (l ppm): 20.3, C(2); 20.4, C(6); 22.1,

C(20); 25.8, C(19); 29.6, C(7); 38.4, C(3); 40.2, C(10);

40.7, C(1); 47.7(5), C(5); 56.7, 12-OMe; 58.1, C(4);

108.7, C(11); 109.1, C(13); 122.2, C(4%); 129.7, C(8);

130.2, C(6%); 133.7, C(14); 136.6, C(5%); 150.2(3), C(3%);

150.2(9), C(9); 154.2, C(1%); 157.4, C(12). Mass spec-

troscopy: m/z 433 [M⁺, 2], 431 (2, M⁺), 322 (10,

added to a solution of 13 (0.999 g, 3.11 mmol) in THF

(6 ml) cooled to −78°C. After 4 min the solution was

added to Cr(CO)₆(3.69 mmol) in ether (10 ml) at 0°C.

After 40 min methyl triﬂate (0.6 ml, 5.3 mmol) was

added, producing a deep red solution which was stirred

at room temperature for 40 min. The solution was

diluted with ether, washed with aqueous sodium hydro-

gencarbonate and dried. Radial chromatography (hex-

anes/ether, 9:1) gave: (i) pentacarbonyl[(methoxy)-

(13 - (12 - methoxy - 19 - norpodocarpa - 4(18),8,11,13-

tetraene)carbene]chromium (9) (1.068 g, 72%) as a red

solid, m.p. 79–81°C. Found: M⁺476.0942. Calc. for

C₂₄H₂₄CrO₇: 476.0327. w_max(cm⁻¹): 2060 (CꢀO), 2015

1

(CꢀO), 1943 (CꢀO). u_max(log₁₀m): 403 nm (3.94). H-

NMR (l ppm): 1.02 (s, H(20)); 1.60 (ddd, J=12.8,

12.8, 4.3 Hz, H(1ax)); 1.68−1.89 (m, H(2ax), H(2eq),

H(6ax), H(6eq)); 2.08 (ddd, J=12.9, 12.9, 5.4 Hz,

H(3ax)); 2.21 (bd, J=10.6 Hz, H(5)); 2.23 (bd, J=12.3

Hz, H(1eq)); 2.39 (ddd, J=13.1, 3.8, 2.2 Hz, H(3eq));

2.83–2.85 (m, H(7ax), H(7eq)); 3.78 (s, 12-OMe); 4.18

(bs, OMe_carbene); 4.62 (d, J=1.2 Hz, H(18)); 4.87 (d,

J=1.2 Hz, H(18)); 6.49 (s, H(14)); 6.78 (s, H(11)).

¹³C-NMR (l ppm): 21.2, C(6); 22.8, C(20); 23.6, C(2);

29.2, C(7); 36.2, C(3); 38.4, C(1); 39.8, C(10); 47.5(5),

C(5); 55.2, 12-OMe; 65.4, OMe_carbene; 106.8, C(18);

107.5, C(11); 122.0, C(14); 127.2, C(13); 148.9, C(9),

C(12); 150.1, C(4); 216.1, CꢀO_cis; 225.3, CꢀO_trans; 355.4,

C_carbene; (C(8) not observed). Mass spectroscopy: m/z

433−C₅H₅NS ), 320 (10, 431−C₅H₅NS ), 307 (18,

+

322−Me ), 305 (18, 320−Me ), 112 (100, C₅H₆NS ).

3.5. 13-Bromo-12-methoxypodocarpa-4(18),8,11,13-

tetraene (13)

A solution of m-chloroperoxybenzoic acid (0.542 g,

2.67 mmol) in dichloromethane (15 ml) was added to a

stirred solution of 12 (1.076 g, 2.67 mmol) in

dichloromethane (10 ml) at −78 °C under a nitrogen

atmosphere. After 1 h the solution was allowed to

warm to room temperature and added to sodium-dried

benzene (100 ml) at reﬂux. After 3 h the solution was

cooled to room temperature. Flash chromatography

(hexanes/ether, 9:1) gave 13-bromo-12-methoxy-19-nor-

podocarpa-4(18),8,11,13-tetraene (13) (0.697 g, 87%) as

+

446 [M , 10], 431 (10, M−Me ), 418 (4, M−CO), 390

(5, M−2CO), 362 (3, M−3CO), 334 (20, M−4CO),

306 (100, M−5CO), 263 (34), 52 (56, Cr); and (ii)

[(methoxy)(13-(h-12-methoxy-19-norpodocarpa4(18),

8,11,13-tetraene))carbene-C¹³,O¹²]chromium (14) (65

mg, 5%) as a black solid, m.p. 155°C (dec.). Found:

M^+.448.0991. Calc. for C₂₃H₂₄CrO₆: 448.0978. w_max

(cm⁻¹): 2015 (s, CꢀO), 1909 (sh, CꢀO), 1845 (br, CꢀO).

¹H-NMR (l ppm): 1.00 (s, H(20)); 1.57 (ddd, J=12.8,

12.8, 4.3 Hz, H(1ax)); 1.67–1.90 (m, H(2ax), H(2eq),

H(6ax), H(6eq)); 2.05 (ddd, J=13.1, 13.1, 5.1 Hz,

H(3ax)); 2.15–2.21 (m, H(5), H(1ax)); 2.39 (ddd, J=

13.1, 4.1, 2.2 Hz, H(3eq)); 2.85 (ddd, J=16.7, 11.6, 5.4

Hz, H(7ax)); 2.92 (ddd, J=16.7, 6.5, 1.8 Hz, H(7eq));

4.20 (s, 12-OMe); 4.62 (d, J=1.1 Hz, H(18)); 4.86 (s,

OMe_carbene); 4.89 (d, J=1.2 Hz, H(18)); 6.88 (s, H(14));

7.27 (s, H(11)). ¹³C-NMR (l ppm): 21.1, C(6);

22.6, C(20); 23.4, C(2); 29.1, C(7); 36.0, C(3); 38.2,

C(1); 40.4, C(10); 47.3, C(5); 64.5, 12-OMe; 67.8,

colourless needles, m.p. 120–122°C. Found: M⁺

,

322.0754. Calc. for C₁₇H₂₁BrO: 322.0755. Found: M⁺

81

22

320.0771. Calc. for C₁₇H BrO: 320.776. w_max(cm⁻¹):

79

1647 (CꢁC_alkene), 1595 (CꢁC), 1257 (CꢂOꢂC_assym), 882

1

(CH). H-NMR (l ppm): 1.01 (s, H(20)); 1.57 (ddd,

J=12.9, 4.7 Hz, H(1ax)); 1.67–1.87 (m, H(2ax),

H(2eq), H(6ax), H(6eq)); 2.06 (ddd, J=13.1, 4.5 Hz,

H(3ax)); 2.17 (bd, J=12.1 Hz, H(5)); 2.23 (bd, J=12.7

Hz, H(1eq)); 2.38 (ddd, J=13.0, 4.3, 2.2 Hz, H(3eq));

2.81 (4 lines, H(7ax), H(7eq)); 4.60 (d, J=1.5 Hz,

H(18)); 4.86 (d, J=1.5 Hz, H(18)); 3.86 (s, 12-OMe);

6.82 (s, H(11)); 7.24 (s, H(14)). ¹³C-NMR (l ppm):

21.2, C(6); 22.7, C(20); 23.6, C(2); 28.8, C(7); 36.2,

C(3); 38.4, C(1); 39.6, C(10); 47.6, C(5); 56.3, 12-OMe;

106.8, C(18); 108.8, C(13); 109.3, C(11); 129.1, C(8);

133.4, C(14); 147.7, C(4); 150.0, C(9); 153.8, C(12).

Mass spectroscopy: m/z 322 [M⁺, 45], 320 (45, M⁺),

.

305 (11, 322−Me ), 303 (11, 320−Me ), 226 (100,

M−Me −Br ).

OMe_carbene

C(14); 129.0, C(13); 130.5, C(8); 149.4, C(4); 154.1(5),

C(9); 163.6, C(12); 213.9, CꢀO_(trans_CO); 231.2(5),

;

107.3, C(18), 107.4, C(11); 118.2,

3.6. Pentacarbonyl[(methoxy)(13-(12-methoxy-

19-norpodocarpa-4(18),8,11,13-tetraene))carbene]-

chromium (9)

to

CꢀO_{(trans to carbene)}; 232.1, CꢀO_{(trans to OMe)}; 333.9, C_carbene

.

Mass spectroscopy: m/z 448 [M⁺, 5], 420 (5,

M−CO), 392 (1, M−2CO), 364 (20, M−3CO), 336

(100, M−4CO), 52 (35, Cr).

Butyllithium (1.49 ml, 2.09 mol l⁻¹, 3.11 mmol) was

210

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

3.9. Pentacarbonyl[(methylamino)(2-methoxyphenyl)-

carbene]chromium (18)

3.7. Pentacarbonyl[(aziridinyl)(2-methoxyphenyl)-

carbene]chromium (16)

Methylamine gas (from KOH, 8 g, and methylamine

hydrochloride, 10 g) was added to a solution of 15 (0.53

g, 1.55 mmol) in THF (15 ml) at −78°C, causing a

colour change from red to yellow. Column chromatog-

raphy (hexanes/ether, 1:1) gave pentacarbonyl[(methyl-

amino)-(methoxyphenyl)carbene]chromium (18) (0.493

Aziridine (0.50 ml, 9.65 mmol) was added to a so-

lution of 15 [45] (0.39 g, 1.15 mmol) in THF (8 ml).

The solution was stirred for 17.5 h under nitrogen,

the colour changing from red to yellow-orange. The

solvent was removed and column chromatography

(hexanes/ether, 1:1) gave pentacarbonyl[(aziridinyl)(2-

methoxyphenyl)carbene]chromium (16) (0.35 g, 86%)

as bright yellow crystals, m.p. 132–133°C. Found:

M⁺352.9968. Calc. for C₁₅H₁₁Cr NO₆: 352.9991. w_max

(CHCl₃, cm⁻¹): 2055 (s, CꢀO), 1975 (sh, CꢀO), 1930

(br, CꢀO). ¹H-NMR (CHCl₃-d, l ppm): 2.58 (dd,

Jꢁ5.6 Hz, CH_2(E)); 3.24 (dd, J=5.6 Hz, CH_2(Z)); 3.78

(s, OMe); 6.83 (dd, J=7.5, 1.5 Hz, H(6)); 6.91 (d,

J=8.3 Hz, H(3)); 6.99 (t, J=7.5 Hz, H(5)); 7.24

g, 94%) as a yellow oil. Found: M⁺340.9984. Calc. for

C₁₄H₁₁CrNO₆: 340.9991. w_max(CHCl₃, cm⁻¹): 2056 (s,

CꢀO), 1976 (sh, CꢀO), 1929 (br, CꢀO). ¹H-NMR

(CHCl₃-d, l ppm): 2.94 (d, J=4.8 Hz, NCH_3(E)); 3.73

(d, J=5.0 Hz, NCH_3(Z)); 3.78 (s, OCH_3(Z)); 3.82 (s,

OCH_3(E)); 6.73 (dd, J=7.5, 1.6 Hz, H(6)_(E)); 6.77 (dd,

J=7.5, 1.7 Hz, H(6)_(Z)); 6.88 (d, J=8.3 Hz, H(3)_(Z));

6.92 (d, J=8.3 Hz, H(3)_(E)); 6.96 (td, J=7.5, 0.8 Hz,

H(5)_(Z)); 7.02 (td, J=7.5, 0.9 Hz, H(5)_(E)); 7.20–7.25

1

(ddd, J=8.3, 7.5, 1.6 Hz, H(4)). H-NMR (C₆H₆-d₆,

(m, H(4)); 8.78 (bs, NH_(Z)); 9.12 (bs, NH_(E)). H-NMR

(C₆H₆-d₆, l ppm): 1.83 (d, J=4.9 Hz, NCH_3(E)); 2.77

(d, J=5.0 Hz, NCH_3(Z)); 3.06 (s, OCH₃); 3.27 (s,

OCH₃); 6.38 (bd, J=8.3 Hz, H(3)); 6.53 (bd, J=7.2

Hz, H(6)); 6.75 (bt, J=7.2 Hz, H(5)); 6.90 (bt, J=7.5

Hz, H(4)); 7.43 (bs, NH_(Z)); 8.39 (bs, NH_(E)). ¹³C-NMR

(CHCl₃-d, l ppm): 37.4, NCH_3(E); 39.8, NCH_3(Z); 55.1,

l ppm): 1.38 (dd, J=5.3 Hz, CH_2(E)); 2.20 (dd, J=

5.3 Hz, CH_2(Z)); 3.26 (s, OMe); 6.46 (d, J=8.0 Hz,

H(3)); 6.74 (dd, J=7.5, 2.1 Hz, H(6)); 6.79 (t, J=7.5

Hz, H(5)); 6.95 (ddd, J=8.0, 7.5, 2.1 Hz, H(4)). ¹³C-

NMR (CHCl₃-d, l ppm): 27.6, CH_2(Z); 28.4, CH_2(E)

;

55.4, OMe; 111.1, C(3); 120.5, C(5); 122.3, C(6);

128.5, C(4); 140.8, C(1); 150.1, C(2); 217.5, CꢀO_cis;

224.1, CꢀO_trans; 270.2, C_carbene. Mass spectroscopy: m/z

353 [M⁺, 7], 325 (10, M−CO), 297 (9, M−2CO), 269

(12, M−3CO), 241 (29, M−4CO), 213 (31,

M−5CO), 185 (83, 213−CH₂CH₂), 170 (40), 133

(35,185−Cr), 52 (100, Cr).

OCH_3(Z); 55.3, OCH_3(E); 110.8,C(3)_(E); 110.9, C(3)_(Z)

;

120.3, C(5)_(Z); 120.7, C(5)_(E); 120.9, C(6)_(E); 121.6,

C(6)_(Z); 128.3, C(4)_(E); 128.5, C(4)_(Z); 137.7, C(1); 148.7,

C(2)_(E); 150.3, C(2)_(Z); 217.3, CꢀO_cis; 223.4, CꢀO_trans(E)

;

.

224.0, CꢀO_trans(Z); 280.8, C_carbene(Z); 281.3, C_carbene(E)

Mass spectroscopy: m/z 341 [M⁺, 3], 313 (14, M−

CO), 285 (7, M−2CO), 257 (10, M−3CO), 229 (20,

M−4CO), 201 (100, M−5CO), 186 (53, 201−Me^.),

52 (47, Cr).

3.8. Pentacarbonyl[(dihydroamino)(2-methoxyphenyl)-

carbene]chromium (17)

3.10. Pentacarbonyl[(dimethylamino)(2-methoxyphenyl)-

carbene]chromium (19)

Liquid ammonia was condensed into a solution of

15 (0.22 g, 6.45 mmol) in THF (10 ml) at 0°C until

the solution colour changed from red to yellow.

Column chromatography (hexanes/ether, 1:1) gave

pentacarbonyl[(dihydroamino)(methoxyphenyl)car-

bene]chromium (17) (0.21 g, 99%) as yellow crystals,

Dimethylamine (0.90 ml, 13.6 mmol) was added to

a solution of 15 (0.59 g, 1.73 mmol). The solution

was stirred for 16.5 h under nitrogen. Column chro-

matography (hexanes/ether, 1:1) gave pentacar-

bonyl[(dimethylamino)(2

-

methoxyphenyl)carbene]-

m.p. 73–75°C. Found: M⁺326.9835. Calc. for

chromium (19) (0.57 g, 92%) [32] as a yellow solid,

m.p. 70.5–71°C. Found: M⁺355.0138. Calc. for

C₁₃H₉O₆CrN: M 326.9835. w_max(cm⁻¹): 2058 (s,

C₁₅H₁₃CrNO₆: 355.0148. w_max(cm⁻¹): 2054 (s, CꢀO),

1973 (sh, CꢀO), 1926 (br, CꢀO). ¹H-NMR (l ppm):

3.06 (s, NCH_3(E)); 3.79 (s, OMe); 3.97 (s, NCH_3(Z));

6.67 (dd, J=7.5 (1.6 Hz, H(6)); 6.87 (d, J=8.2 Hz,

H(3)); 6.99 (t, J=7.5 Hz, H(5)); 7.16 (td, J=8.3, 7.5,

1.6 Hz, H(4)). ¹³C-NMR (l ppm): 45.3, CH_3(Z); 50.9,

CH_3(E); 55.1, OCH₃; 110.8, C(3); 120.4, C(5); 120.7,

C(6); 127.4, C(4); 141.1, C(1); 148.1, C(2); 217.4,

CꢀO_cis; 224.0, CꢀO_trans; 272.6, C_carbene. Mass spec-

troscopy: m/z 355 [M⁺, 2], 327 (7, M−CO), 299 (12,

M−2CO), 271 (8, M−3CO), 243 (25, M−4CO),

215 (100, M−5CO), 200 (48, 215−Me), 52 (45, Cr).

1

CꢀO), 1979 (sh, CꢀO), 1934 (br, CꢀO). H-NMR (l

ppm): 3.82 (s, OCH₃); 6.90–6.93 (m, H(3), H(6)); 7.00

(td, J=7.5, 1.0 Hz, H(5)); 7.27 (ddd, J=8.7, 7.1, 1.7

Hz, H(4)); 8.46 (bs, NH_Z); 9.01 (bs, NH_E). ¹³C-NMR

(l ppm): 55.2, OMe; 111.1, C(3); 120.5(5), C(5);

122.4(5), C(6); 129.6, C(4); 141.1(5), C(1); 150.8, C(2);

217.1, CꢀO_cis; 223.5, CꢀO_trans; 290.9, C_carbene. Mass

spectroscopy: m/z 327 [M⁺, 8], 299 (13, M−CO),

271 (10, M−2CO), 243 (13, M−3CO), 215, (23,

M−4CO), 187 (100, M−5CO), 172 (187−Me ), 52

(58, Cr).

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

211

3.11. Pentacarbonyl[(pyrrolidinyl)(2-methoxyphenyl)-

carbene]chromium (20)

(ii) Morpholine (2.4 ml, 28 mmol) was added to a

solution of 15 (0.48 g, 1.39 mmol) in THF (12 ml) at

room temperature in a foil-covered ﬂask. The solu-

tion was stirred under nitrogen for 20 h. Workup

gave morpholine(pentacarbonyl)chromium (21) (0.11 g,

28%).

Pyrrolidine (1.0 ml, 12 mmol) was added to a solution

of 15 in THF (10 ml). The solution was stirred for 19 h

under nitrogen, the colour changing from red to yellow.

Column chromatography (hexanes/ether, 1:1) gave pen-

tacarbonyl[(pyrrolidinyl)(2-methoxyphenyl)carbene]-

chromium (20) (0.67 g, 96%) as pale yellow crystals, m.p.

111–112.5°C. Found: M⁺381.0298. Calc. for

C₁₇H₁₅CrNO₆: M, 381.0304. w_max(CHCl₃, cm⁻¹): 2052

3.13. Pentacarbonyl[(morpholino)phenylcarbene]-

chromium (22)

Sodium naphthalenide (from sodium, 70 mg, and

naphthalene, 0.29 g) was added to Cr(CO)₆(0.23 g, 1.05

mmol) in THF (6 ml) at −78°C; the mixture was warmed

slowly to 0°C and stirred for 20 min. The reddish-yellow

solution of Na₂Cr(CO)₅was cooled to −78°C, and a

solution of 23 [38] (0.10 g, 0.533 mmol) in THF (2 ml)

was added rapidly. After 40 min the solution was warmed

to 0°C for 45 min and then cooled to −78 °C. Me₃SiCl

(0.20 ml, 1.58 mmol) was added rapidly and the solution

was stirred for 1.5 h. Alumina (2 g) was added and the

brownish yellow slurry was warmed to room tempera-

ture. Column chromatography (1:1, hexanes/ether eluted

pentacarbonyl[(morpholino)phenylcarbene]chromium

(22) (94 mg, 48%) as yellow crystals, m.p. 98–101°C.

1

(s, CꢀO), 1971 (sh, CꢀO), 1932 (br, CꢀO). H-NMR

(CHCl₃-d, l ppm): 1.98 (m, CH₂CH₂N_(E)); 2.19 (5 lines,

J=13.8, 7.1, 7.0 Hz, CH₂CH₂N_(Z)); 3.19 (ddd, J=13.3,

7.5, 6.9 Hz, CH_axN_(E)); 3.35 (ddd, CH_eqN_(E)); 3.80 (s,

OCH₃); 4.24 (5 lines, J=13.3, 7.3, 6.8 Hz, CH_axN_(Z));

4.30 (5 lines, J=13.3, 7.0, 6.6 Hz, CH_eqN_(Z)); 6.68 (dd,

J=7.5, 1.6 Hz, H(6)); 6.88 (d, J=8.3 Hz, H(3)); 6.99 (td,

J=7.4, 0.7 Hz, H(5)); 7.16 (td, J=8.3, 1.6 Hz, H(4)).

¹H-NMR (C₆H₆-d₆, l ppm): 1.00, m, CH₂CH₂N); 1.16

(5 lines, J=13.8, 6.8, 6.7 Hz, CH₂CH₂N); 2.64 (m,

CH₂N_(E)); 3.33 (s, OCH₃); 3.77 (5 lines, J=13.1, 7.5, 6.9

Hz, CH_axN_(Z)); 3.91 (5 lines, J=13.2, 6.9, 6.7 Hz,

CH_eqN_(Z)); 6.50 (d, J=8.2 Hz, H(3)); 6.56 (dd, J=7.4,

1.3 Hz, H(6)); 6.84 (t, J=7.4 Hz, H(5)); 6.93 (ddd,

J=8.2, 7.4, 1.2 Hz, H(4)). ¹³C-NMR (CHCl₃-d, l ppm):

25.3(0), CH₂CH₂N_(E); 25.3(3), CH₂CH₂N_(Z); 55.16,

OCH₃; 55.19, CH₂N_(E); 59.0, CH₂N_(Z); 110.9(5), C(3);

119.9(5), C(5); 120.8(5), C(6); 127.2, C(4); 142.2, C(1);

Found M⁺367.0145. Calc. for C₁₆H₁₃CrNO₆: 367.0148.

w_max(cm⁻¹): 2055 (s, CꢀO), 1973 (sh, CꢀO), 1928 (br,

CꢀO). ¹H-NMR (CHCl₃-d, l ppm): 3.50 (3 lines, J=5.2,

4.4 Hz, NCH_2(E)); 3.62 (3 lines, J=5.2, 4.5 Hz, OCH_2(E));

4.08, 3 lines, J=4.9 Hz, OCH_2(Z)); 4.58 (3 lines, J=4.9

Hz, NCH_2(Z)); 6.71 (dd, J=8.3, 1.2 Hz, H_ortho); 7.18 (tt,

J=7.5, 1.2 Hz, H_para); 7.02 (tt, J=8.3, 7.5, 1.7 Hz,

H_meta). ¹H-NMR (C₆H₆-d₆, l ppm): 2.56, (3 lines, J=4.9

Hz, NCH_2(E)); 2.72 (3 lines, J=5.1, 4.0 Hz, OCH_2(E));

3.40 (3 lines, J=4.9 Hz, OCH_2(Z)); 3.93 (3 lines, J=4.9

Hz, NCH_2(Z)); 6.31 (dd, J=7.8, 1.4 Hz, H_ortho); 6.82 (tt,

J=7.4, 1.2 Hz, H_para); 7.02 (bt, J=7.8, 7.4 Hz, H_meta).

¹³C-NMR (CHCl₃-d, l ppm): 55.3, NCH_2(Z); 60.4,

147.9, C(2); 217.7, CꢀO_cis; 224.0, CꢀO_trans; 266.9, C_carbene

.

Mass spectroscopy: m/z 381 [M⁺, 2], 353 (10, M−CO),

325 (8, M−2CO), 297 (8, M−3CO), 267 (18, M−

4CO), 241 (100, M−5CO), 226 (38, 241−Me ), 121

(45), 91 (45), 52 (42, Cr).

3.12. Pentacarbonyl[(morpholino)(2-methoxyphenyl)-

carbene]chromium: attempted synthesis

(i) Morpholine (0.40 ml, 4.6 mmol) was added to a

solution of 15 (0.20 g, 5.75 mmol) in THF (10 ml) at room

temperature. The solution was stirred under nitrogen for

25 h. Column chromatography gave: (i) a mixture of 15

and tetracarbonyl[(methoxy)(2-methoxyphenyl)carbene-

C¹,O²]chromium (27 mg); and (ii) (morpho-

line)pentacarbonylchromium (21) (59 mg, 37%) as yellow

crystals, m.p. 111–112°C (lit. [36] m.p. 112°C). Found:

NCH_2(E); 67.8, OCH_2(E); 68.1, OCH_2(Z); 119.1, C_ortho

;

126.1, C_para; 128.6, C_meta; 151.2, C_ipso; 217.0, CꢀO_cis;

223.6, CꢀO_trans; 274.6, C_carbene. Mass spectroscopy: m/z

367 [M⁺, 1], 350 [5, ((morpholine)PhC)₂Found: M⁺

350.1990. Calc. for C₂₂H₂₆N₂O₂: 350.1994)], 339 (8,

M−CO), 311 (7, M−2CO), 283 (5, M−3CO), 264 (10,

350−C₄H₈NO ), 255 (8, M−4CO), 227 (100, M−

5CO) 105 (50), 91 (68), 77 (29, Ph⁺), 52 (45, Cr).

M⁺, 278.9841. Calc. for C₉H₉CrNO₆: M, 278.9835. w_max

(cm⁻¹): 2067 (s, CꢀO), 1980 (sh, CꢀO), 1932 (br, CꢀO).

¹H-NMR (l ppm): 2.22, bs, NH); 2.87–2.99 (m, CH₂N

(4H)); 3.43 (ddd, J=12.0, 11.6, 3.3 Hz); CHO (2H)); 3.80

(bd, J=12.7 Hz, CHO (2H)). ¹³C-NMR (l ppm): 56.6,

CH₂N; 68.3, CH₂O; 213.7, CꢀO_cis; 219.6, CꢀO_trans. Mass

spectroscopy: m/z 279 [M⁺, 7], 251 (2, M−CO), 223 (4,

M−2CO), 195 (1, M−3CO), 167 (10, M−4CO), 139

(40, M−5CO), 87 (73, C₄H₉NO⁺), 57 (100, C₃H₇N⁺),

52 (43, Cr).

3.14. (N-Morpholino)-2-methoxyphenylamide (24)

A solution of 2-methoxybenzoic acid (2.09 g, 13.7

mmol) in thionyl chloride (4.0 g, 34 mmol) was heated

to 50°C for 30 min. The excess thionyl chloride was

removed in vacuo, and the residue was dissolved in

CH₂Cl₂(10 ml). Morpholine (5.0 ml, 57 mmol) was

added dropwise to the solution at 0°C and the white

212

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

m/z 410 (1,(MeOPh(morpholino)C)₂), 397 [M⁺, 2], 369

slurry was stirred for 1 h. The suspension was diluted

with CH₂Cl₂(50 ml). Workup gave (N-morpholino)-2-

methoxyphenylamide (24) (2.75 g, 91%) as a waxy,

(9, M−CO), 341 (8, 369−CO), 313 (8, 341−CO), 285

(22, 313−CO), 257 (100, 285−CO), 242 (23, 257−

Me), 52 (46, Cr).

white solid, m.p. 50–52°C. Found: M⁺221.1047. Calc.

for C₁₂H₁₅NO₃: 221.1052. w_max(cm⁻¹): 1634 (CꢁO).

¹H-NMR (l ppm): 3.26 (dt, J=16.9, 4.4 Hz, NCH_2(E));

3.60 (dq, J=16.6, 3.7 Hz, OCH_2(E)); 3.74–3.88 (m,

NCH_2(Z), OCH_2(Z)); 3.84 (s, OMe); 6.91 (d, J=8.3 Hz,

H(3)); 7.00 (td, J=7.4, 0.7 Hz, H(5)); 7.25 (dd, J=7.5,

1.7 Hz, H(6)); 7.36 (ddd, J=8.3, 7.4, 1.7 Hz, H(4)).

3.16. Pentacarbonyl[(dihydroamino)-

(13-(12,19-dimethoxypodocarpa-8,11,13-triene))

carbene]chromium (26)

Ammonia gas was condensed into a solution of 7

(0.42 g, 0.80 mmol) in THF (10 ml) until the solution

colour changed from red to orange-yellow. Radial

chromatography (hexanes/ether, 1:1) gave pentacar-

bonyl[(dihydroamino)(13-(12,19-dimethoxypodocarpa-

8,11,13-triene))carbene]chromium (26) (0.36 g, 89%) as

yellow crystals, m.p. 133–136°C. Found: C, 59.23; H,

5.81; N, 2.79.Calc. for C₂₅H₂₉CrNO₇: C, 59.17; H, 5.76;

¹³C-NMR (l ppm): 42.0(5), NCH_2(Z); 47.2, NCH_2(E)

;

55.5, OCH₃; 66.8, OCH_2(E); 66.9, OCH_2(Z); 110.8, C(3);

120.9(5), C(5); 125.2, C(1); 128.0, C(6); 130.5, C(4);

155.2, C(2); 167.8, CꢁO. Mass spectroscopy: m/z 221

+

[M , 11], 220 (13, M−H), 135 (100, M−C₄H₈NO ),

77 (18, Ph).

N, 2.76%. Found: M⁺

507.1382. Calc. for

3.15. Pentacarbonyl[(morpholino)(2-methoxyphenyl)-

carbene]chromium (25)

C₂₅H₂₉CrNO₇: 507.1349%. w_max(cm⁻¹): 2052 (s, CꢀO),

1971 (sh, CꢀO), 1926 (br, CꢀO). ¹H-NMR (l ppm):

1.02 (ddd, J=13.5, 4.1 Hz, H(3ax)); 1.05 (s, H(18));

1.21 (s, H(20)); 1.42 (dd, J=12.7, 1.8 Hz, H(5)); 1.43

(ddd, J=13.0, 3.8 Hz, H(1ax)); 1.61–1.80 (m, H(2ax),

H(2eq), H(6ax)); 1.88 (bd, J=13.5 Hz, H(3eq)); 1.99

(bdd, J=13.4, 7.2 Hz, H(6eq)); 2.27 (bd, J=12.4 Hz,

H(1eq)); 2.77 (ddd, J=16.9, 11.3, 7.2 Hz, H(7ax)); 2.87

(bdd, J=16.9, 5.6 Hz, H(7eq)); 3.25 (d, J=9.1, H(19));

3.33 (s, 19-OMe); 3.52 (d, J=9.1 Hz, H(19)); 3.80 (s,

12-OMe); 6.74 (s, H(14)); 6.77 (s, H(11)); 8.65 (bs,

NH_(Z)); 8.94 (bs, NH_(E)). ¹³C-NMR (l ppm): 19.1, C(2);

19.2, C(6); 25.5, C(20); 27.6, C(18); 30.1, C(7); 35.9,

C(3); 38.0, C(10); 38.2, C(4); 39.0, C(1); 51.1, C(5);

55.3, 12-OMe; 59.4, 19-OMe; 75.9, C(19); 107.1, C(11);

125.5, C(14); 127.2, C(13); 137.7, C(8); 149.8, C(12);

155.2, C(9); 217.4, CꢀO_cis; 223.6, CꢀO_trans; 288.1,

Sodium naphthalenide (from sodium, 0.29 g, and

naphthalene, 1.557 g) was added to Cr(CO)₆(1.25 g,

5.56 mmol) in THF (15 ml) at −78°C, and the mixture

was slowly warmed to 0°C, and stirred for 10 min. The

red-orange solution of Na₂Cr(CO)₅was cooled to

−78°C, and a solution of 24 (0.79 g, 3.59 mmol) in

THF (5 ml) was added rapidly. After 30 min the

solution was then warmed to 0°C for 1 h then cooled to

−78°C, followed by the addition of Me₃SiCl (1.60 ml,

12.6 mmol). The mixture was stirred at −78°C for 1 h,

oven-dried alumina (10 g) was added, and the yellow

slurry was warmed to room temperature. Column chro-

matography (hexanes/ether, 1:1) gave pentacarbonyl-

[(morpholino)(2-methoxyphenyl)carbene]chromium (25)

(1.13 g, 79%) as a yellow crystalline solid, m.p. 94–

96°C. Found: M⁺397.0240. Calc. for C₁₇H₁₅CrNO₇:

C

_carbene. Mass spectroscopy: m/z 507 [M⁺, 1], 479 (3.

397.0254. w_max(cm⁻¹): 2055 (s, CꢀO), 1973 (sh, CꢀO),

M−CO), 451 (2, M−2CO), 423 (1, M−3CO), 395

(18, M−4CO), 367 (100, M−5CO), 352 (24, 367−

Me^.), 186 (93), 52 (53, Cr).

1

1928 (br, CꢀO). H-NMR (CHCl₃-d, l ppm): 3.42–3.57

(m, NCH_2(E)); 3.57–3.68 (m, OCH_2(E)); 3.80 (s, OMe);

4.02 (7 lines, J=12.0, 8.4, 3.0 Hz, CH_axO_(Z)); 4.09 (8

lines, J=12.0, 8.6, 3.0 Hz, CH_eqO_(Z)); 4.43 (8 lines,

J=13.1, 7.8, 3.2 Hz, CH_axN_(Z)); 4.71 (10 lines, J=

13.0, 7.8, 3.2 Hz, CH_eqN_(Z)); 6.69 (dd, J=7.5, 1.5 Hz,

H(6)); 6.88 (d, J=8.2 Hz, H(3)); 7.00 (td, J=7.6, 0.5

3.17. Pentacarbonyl[(methylamino)-

(13-(12,19-dimethoxypodocarpa-8,11,13-triene))-

carbene]chromium (27)

1

Hz, H(5)); 7.18 (ddd, J=8.2, 7.6, 1.5 Hz, H(4)). H-

Methylamine gas (from KOH, 22 g, and methyl-

amine hydrochloride, 19 g) was added to a solution of

7 (0.42 g, 0.79 mmol) until the colour changed from red

to yellow. Radial chromatography (hexanes/ether, 1:1)

gave pentacarbonyl[(methylamino)(13-(12,19-dimeth-

NMR (C₆H₆-d₆, l ppm): 2.65 (b, NCH_(E)); 2.82 (b,

NCH_(E)); 2.85 (b, OCH_(E)); 2.99 (b, OCH_(E)); 3.22 (s,

OMe); 3.44 (b, OCH_ax(Z)); 3.48 (2 lines, J=5.7 Hz,

OCH_eq(Z)); 3.85 (b, NCH_ax(Z)); 4.17 (2 lines, J=9.3 Hz,

NCH_eq(Z)); 6.40 (bd, J=7.8 Hz, H(3)); 6.46 (bd, J=6.8

Hz, H(6)); 6.79 (bt, J=6.8 Hz, H(5)); 6.87 (bt, J=7.0

Hz, H(4)). ¹³C-NMR (CHCl₃-d, l ppm): 55.0, OCH₃;

55.1, NCH_2(E); 60.0(5), NCH_2(Z); 67.2, OCH_2(E); 67.9,

OCH_2(Z); 110.7, C(3); 120.6(7), C(5); 120.7(2), C(6);

127.6, C(4); 139.6, C(1); 148.2, C(2); 217.2, CꢀO_cis;

223.8, CꢁO_trans; 270.9(5), C_carbene. Mass spectroscopy:

oxypodocarpa-8,11,13-triene)carbene]chromium

(27)

(0.34 g, 82%) as a pale yellow solid, m.p. 117–119°C

(hexanes). The E/Z isomer ratio is 3:2, the E isomer

being a mixture (1:1) of rotamers. Found: C,59.82; H,

6.00; N, 2.59. Calc. for C₂₆H₃₁CrNO₇: C, 59.92; H,

6.00; N, 2.69%. Found: M^+.521.1507. Calc. for

C₂₆H₃₁CrNO₇: 521.1506%. w_max(CH₂Cl₂, cm⁻¹):

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

213

1

2052 (s, CꢀO), 1971 (sh, CꢀO), 1926 (br, CꢀO). H-

NMR (l ppm): 1.00 (b, H(3ax)); 1.04 (s, H(18)_(E)); 1.05

(s, H(18)_(Z)); 1.19 (s, H(20)_(E)); 1.20 (s, H(20)_(Z)); 1.21 (s,

H(20)_(E)); 1.40–1.47 (m, H(1ax), H(5)); 1.60–1.80

(H(2ax), H(2eq), H(6ax)); 1.87 (bd, J=10.9 Hz,

H(3eq)); 1.97 (bdd, J=13.1, 7.5 Hz, H(6eq)); 2.26 (bd,

J=11.5 Hz, H(1eq)); 2.66–2.80 (m, H(7ax)); 2.89 (bdd,

J=11.5, 6.4 Hz, H(7eq)); 2.93 (d, J=4.7 Hz,

NCH_3(E)); 2.94 (d, J=4.6 Hz, NCH_3(E)); 3.24 (d, J=

9.0 Hz, H(19)); 3.34 (s, 19-OMe); 3.52 (d, J=9.0 Hz,

H(19)_(E)); 3.54 (d, J=9.0 Hz, H(19)_(Z)); 3.69 (d, J=5.0

Hz, NCH_3(Z)); 3.73 (s, 12-OMe_(Z)); 3.76 (s, 12-OMe_(E));

6.33 (s, H(14)_(E)); 6.36 (s, H(14)_(E)); 6.42 (s, H(14)_(Z));

6.72 (s, H(11)_(Z)); 6.74 (s, H(11)_(E)); 8.75 (bs, NH_(Z));

9.08 (bs, NH_(E)). ¹³C-NMR (l ppm): 19.2, C(2); 19.3,

C(6); 25.6, C(20)_(E); 25.7, C(20)_(Z); 27.6, C(18); 30.2,

C(7)_(E); 30.4, C(7)_(Z); 35.9, C(3); 37.5, NCH_3(E); 38.0,

C(10); 38.0(6), C(4); 39.1, C(1); 45.3, NCH_3(Z); 50.8,

NCH_3(E); 51.5, C(5); 55.0, 12-OMe; 59.4, 19-OMe; 75.7,

C(19); 106.3, C(11); 120.7, C(14); 126.9, C(13); 139.12,

C(8); 146.4, C(12); 148.9(5), C(9); 217.5, CꢀO_cis; 224.2,

CꢀO_trans; 272.8, C_carbene. Mass spectroscopy: m/z 535

[M⁺, 1], 507 (5, M−CO), 479 (4, M−2CO), 451

(1,M−3CO), 423 (78, M−4CO), 395 (100, M−5CO),

380 (395−Me ).

3.19. Pentacarbonyl[(aziridinyl)(13-(12,19-

dimethoxypodocarpa-8,11,13-triene))carbene]chromium

(29)

Aziridine (0.40 ml, 7.7 mmol) was added to a solu-

tion of (7) (0.451 g, 0.863 mmol) in THF (8 ml). The

solution was stirred at room temperature for 3.5 h.

Radial chromatography (hexanes/ether, 1:1) gave pen-

tacarbonyl[(aziridinyl)(13-(12,19-dimethoxypodocarpa-

8,11,13-triene))carbene]chromium (29) (0.37 g, 81%) as

yellow crystals, m.p. 108–109°C (decomp.). Anal.

Found: C, 61.28; H, 5.93; N, 2.57. Calc. for

C₂₇H₃₁CrNO₇: C, 60.78; H, 5.86; N, 2.63%. Found

C(10), C(4); 39.1, C(1); 39.8, NCH_3(Z); 51.0, C(5)_(E)

51.2, C(5)_(Z); 51.4, C(5)_(E); 55.0(5), 12-OMe_(Z); 55.2,

12-OMe_(E); 59.4, 19-OMe; 75.8, C(19)_(E); 75.9, C(19)_(Z)

;

76.0, C(19)_(E); 106.5, C(11); 106.6(8), C(11); 106.7(4),

C(11); 121.0, C(14); 121.1, C(14); 122.1, C(14); 126.6,

M⁺533.1500. Calc. for C₂₇H₃₁CrNO₇: 533.1506. w_max

C(13); 127.1(5), C(13); 127.2(2), C(13); 135.3, C(8)_(Z)

135.5, C(8)_(E); 147.9(7), C(12)_(E); 147.0(5), C(12)_(Z)

;

(CH₂Cl₂, cm⁻¹): 2054 (s,CꢀO), 1973 (sh, CꢀO), 1929

1

148.7, C(9); 149.9, C(9); 217.4(5), CꢀO_cis; 223.6,

CꢀO_trans(E); 224.2, CꢀO_trans(Z); 268.6, C_carbene; 280.7,

(br, CꢀO). H-NMR (l ppm): 1.03 (ddd, J=13.6, 4.1

Hz, H(3ax)); 1.05 (s, H(18)); 1.21 (s, H(20)); 1.44 (dd,

J=12.7, 2.0 Hz, H(5)); 1.46 (ddd, J=13.0, 3.8 Hz,

H(1ax)); 1.59–1.80 (m, H(2ax), H(2eq), H(6ax)); 1.88

(bdd, J=13.4, 1.1 Hz, H(3eq)); 1.96 (ddt, J=13.5, 7.0,

2.1 Hz, H(6eq)); 2.27 (bd, J=12.2 Hz, H(1eq)); 2.59

(dd, J=5.5, 5.5 Hz, NCH_2(E)); 2.74 (ddd, J=16.8,

11.3, 7.3 Hz, H(7ax)); 2.84 (bdd, J=16.8, 5.6 Hz,

H(7eq)); 3.20 (dd, J=5.2, 5.2 Hz, NCH_(Z)); 3.21 (dd,

J=5.2, 5.2 Hz, NCH_(Z)); 3.25 (d, J=9.1 Hz, H(19));

3.34 (s, 19-OMe); 3.54 (d, J=9.1 Hz, H(19)); 3.73 (s,

12-OMe); 6.48 (s, H(14)); 6.74 (s, H(11)). ¹³C-NMR (l

ppm): 19.1(5), C(2); 19.3, C(6); 25.6, C(20); 26.6, C(18),

CH_2(Z); 28.7, CH_2(E); 30.3, C(7); 35.9, C(3); 38.0(5),

C(4), C(10); 39.0, C(1); 51.1(5), C(5); 55.4, 12-OMe;

59.4, 19-OMe; 75.9, C(19); 106.98, C(11); 122.8(5),

C(14); 126.8, C(13); 138.5, C(8); 148.6, C(12); 150.1(5);

C

_carbene; 281.4, C_carbene. Mass spectroscopy: m/z 521

[M⁺, 2], 493 (4, M−CO), 465 (M−2CO), 437 (2,

M−3CO), 409 (20, M−4CO), 381 (100, M−5CO),

366 (381−Me ), 52 (14, Cr).

3.18. Pentacarbonyl[(dimethylamino)(13-(12,19-

dimethoxypodocarpa-8,11,13-triene)-carbene]chromium

(28)

Dimethylamine (1.0 ml, 15 mmol) was added to a

solution of 7 (0.30 g, 0.574 mmol) in THF (10 ml). The

solution was stirred for 2 h at room temperature.

Radial chromatography (hexanes/ether, 1:1) gave pen-

tacarbonyl[(dimethylamino)(13-(12,19-dimethoxypodo-

carpa-8,11,13-triene))carbene (28) (0.27 g, 89%) as a

yellow solid, m.p. 115 °C (decomp.). Found: M⁺

C(9); 217.6, CꢀO_cis; 224.2, CꢀO_trans; 270.6, C_carbene.

535.1677. Calc. for C₂₇H₃₃CrNO₇: 535.1662. w_max

Mass spectroscopy: m/z 533 [M⁺, 1], 505, (5, M−CO),

477 (1, M−2CO), 449 (1, M−3CO), 421 (25, M−

4CO), 393 (25, M−5CO), 365 (100, 393−C₂H₄), 313

(20, 365−Cr), 180 (53), 52 (42, Cr).

(CH₂Cl₂, cm⁻¹): 2053 (s, CꢀO), 1973 (sh, CꢀO), 1928

1

(br, CꢀO). H-NMR (l ppm): 1.00 (ddd, J=13.3, 3.9

Hz, H(3ax)); 1.04 (s, H(18)); 1.20 (s, H(20)); 1.40 (ddd,

J=13.0, 3.8 Hz, H(1ax)); 1.41 (bd, J=12.3 Hz, H(5));

1.55–1.75 (m, H(2ax), H(2eq), H(6ax)); 1.89 (bd, J=

13.8 Hz, H(3eq)); 1.96 (bdd, J=13.5, 6.9 Hz, H(6eq));

2.27 (bd, J=12.0 Hz, H(1eq)); 2.68 (ddd, J=16.5,

11.8, 7.3 Hz, H(7ax)); 2.87 (bdd, J=16.5, 5.6 Hz,

H(7eq)); 3.06 (s, NCH_3(E)); 3.24 (d, J=9.0 Hz, H(19));

3.34 (s, 19-OMe); 3.55 (d, J=9.0 Hz, H(19)); 3.73 (s,

12-OMe); 3.94 (s, NCH_3(Z)); 6.31 (s, H(14)); 6.69

(H(11)). ¹³C-NMR (l ppm): 19.2, C(2); 19.3, C(6); 25.7,

C(20); 27.6, C(18); 30.4, C(7); 35.9(5), C(3); 38.0(1),

3.20. Pentacarbonyl[(pyrrolidinyl)(13-(12,19-

dimethoxypodocarpa-8,11,13-triene))carbene]chromium

(30)

A solution of pyrrolidine (0.40 ml, 4.8 mmol) and 7

(0.50 g, 0.951 mmol) was stirred at room temperature

for 4 h. Radial chromatography (hexanes/ether, 1:1)

gave pentacarbonyl[(pyrrolidinyl)(13-(12,19-dimethoxy-

podocarpa-8,11,13-triene))carbene]chromium (30) (0.48

214

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

38.7, C(1); 41.8, NCH_2(Z); 47.0, NCH_2(E); 50.9, C(5);

55.3, 12-OMe; 59.0(5), 19-OMe; 66.6, OCH_2(E); 66.7,

OCH_2(Z); 75.5, C(19); 106.7, C(11); 122.4, C(14); 127.4,

C(13); 128.2, C(8); 152.0(5), C(9); 153.0, C(12); 167.8,

CꢁO. Mass spectroscopy: m/z 355 [M⁺, 22], 340 (2,

g, 91%) as a pale yellow solid, m.p. 120°C (decomp.)

(hexanes). Anal. Found: C, 62.51; H, 6.65; N, 2.52.

Calc. for C₂₉H₃₅CrNO₇: C, 62.07; H, 6.29; N, 2.50%.

Found: M⁺561.1833. Calc. for C₂₉H₃₅CrNO₇:

561.1819. w_max(CH₂Cl₂, cm⁻¹): 2052 (s, CꢀO), 1971

(sh, CꢀO), 1925 (br, CꢀO). ¹H-NMR (l ppm): 1.00

(ddd, J=13.5, 4.3 Hz, H(3ax)); 1.04 (s, H(18)); 1.20 (s,

H(20)); 1.40 (ddd, J=12.8, 3.9 Hz, H(1ax)); 1.41 (bd,

J=12.6 Hz, H(5)); 1.60–1.78 (m, H(2ax), H(2eq),

H(6eq)); 1.89 (bd, J=12.6 Hz, H(3eq)); 1.89–2.00 (m,

H(6eq), CH_2(E)CH₂N); 2.17 (ddd, J=13.9, 7.0 Hz,

CH_2(Z)CH₂N); 2.27 (bd, J=12.4 Hz, H(1eq)); 2.68

(ddd, J=16.7, 11.6, 7.1 Hz, H(7ax)); 2.86 (bdd, J=

16.7, 5.9 Hz, H(7eq)); 3.21 (ddd, CH_ax(E)); 3.23 (d,

J=9.1 Hz, H(19)); 3.34 (s, 19-OMe); 3.37 (ddd, J=

13.4, 7.7, 6.8 Hz, CH_eq(E)); 3.55 (d, J=9.1 Hz, H(19));

3.74 (s, 12-OMe); 4.20 (ddd, J=13.2, 7.4, 6.7 Hz,

CH_ax(Z)); 4.26 (ddd, J=13.2, 7.0, 6.7 Hz, CH_eq(Z)); 6.31

(H(14)); 6.70 (H(11)). ¹³C-NMR (l ppm): 19.2, C(2);

19.3, C(6); 25.3, CH_2(E)CH₂N; 25.4, CH_2(Z)CH₂N; 25.7,

C(20); 27.6, C(18); 30.5, C(7); 35.9, C(3); 37.9(8), C(10);

38.0(6), C(4), 39.1, C(1); 51.5, C(5); 55.0(6), 12-OMe;

55.1(2), CH_2(E)N; 58.9, 19-OMe; 59.4, CH_2(Z)N; 75.7,

C(19); 106.5, C(11); 120.1, C(14); 127.0, C(13); 140.2,

C(8); 146.2, C(12); 148.7(5), C(9); 217.8, CꢀO_cis; 224.2,

CꢀO_trans; 267.3, C_carbene. Mass spectroscopy: m/z 561

[M⁺, 8], 533 (14, M−CO), 505 (5, M−2CO), 449

(100, M−4CO), 421 (100, M−5CO), 370 (20, 421−

M−Me ), 269 (100, M−C₄H₈NO).

3.22. Pentacarbonyl[(morpholino)(13-(12,19-

dimethoxypodocarpa-8,11,13-triene))carbene]chromium

(31)

Sodium naphthalenide (from sodium, 0.28 g, and

naphthalene, 1.17 g) was added to Cr(CO)₆(0.23 g, 1.05

mmol) in THF (8 ml) at −78°C. The yellow red

solution of Na₂Cr(CO)₅was cooled to −78°C and a

solution of 32 (0.80 g, 2.07 mmol) in THF (6 ml) was

added rapidly. After 1 h the solution was warmed to

0°C for 1 h, followed by cooling to −78°C. Me₃SiCl

(1.0 ml, 7.9 mmol) was added and the solution was

stirred for 30 min. Alumina (9.5 g) was added and the

yellow-orange slurry was warmed to room temperature.

Column chromatography (hexanes/ether, 1:1) gave pen-

tacarbonyl[(morpholino)(13 - (12,19 - dimethoxypodo-

carpa-8,11,13-triene))carbene]chromium (31) (0.91 g,

76%) as ﬁne yellow plates, m.p. 115–116°C (hexanes).

Anal. Found: C, 60.50; H, 6.05; N, 2.33. Calc. for

C₂₉H₃₅CrNO₈: C, 60.35; H, 6.11; N, 2.43%. Found:

M⁺577.1803. Calc. for C₂₉H₃₅CrNO₈: 577.1768. w_max

Cr−H ).

(cm⁻¹): 2052 (s, CꢀO), 1971 (sh, CꢀO), 1926 (br, CꢀO).

¹H-NMR (l ppm): 0.99 (ddd, J=13.1, 3.2 Hz, H(3ax));

1.04 (s, H(18)); 1.21 (s, H(20), 1.39 (ddd, J=13.0, 3.7

Hz, H(1ax)); 1.40 (dd, J=12.6, 1.8 Hz, H(5)); 1.60–

1.80 (m, H(2ax), H(2eq), H(6ax)); 1.89 (bd, J=13.5

Hz, H(3eq)); 1.96 (bdd, J=13.4, 7.4 Hz, H(6eq)); 2.26

(bd, J=12.4 Hz, H(1eq)); 2.67 (ddd, J=16.8, 11.5, 7.2

Hz, H(7ax)); 2.86 (bdd, J=16.8, 5.9 Hz, H(7eq)); 3.24

(d, J=9.1 Hz, H(19)); 3.34 (s, 19-OMe); 3.40–3.50 (m,

NCH_2(E)); 3.54 (d, J=9.1 Hz, H(19)); 3.63 (m,

OCH_2(E)); 3.74 (s, 12-OMe); 4.00 (ddd, J=12.0, 8.3, 3.0

Hz, OCH_ax(Z)); 4.07 (ddd, J=12.0, 8.6, 3.4 Hz,

OCH_eq(Z)); 4.39 (ddd, J=13.1, 7.6, 3.3 Hz, NCH_ax(Z));

4.68 (ddd, J=13.0, 7.8, 3.2 Hz, NCH_eq(Z)); 6.34 (s,

H(11), 6.69 (s, H(14)). ¹³C-NMR (l ppm): 19.1(5), C(2);

19.3, C(6); 25.7, C(20); 27.5, C(18); 27.6, C(18); 30.4,

C(7); 35.8(7), C(3); 35.9(5), C(3); 37.9, C(10); 38.0,

C(4); 39.1, C(1); 51.0, C(5); 51.4, C(5); 54.9, 12-OMe,

3.21. N-Morpholino-12,19-dimethoxypodocarpa-

8,11,13-triene-13-carboxamide (32)

Butyllithium (4.10 ml, 2.0 mol l⁻¹) was added drop-

wise to a solution of 6 (1.50 g, 4.07 mmol) in THF (40

ml) cooled to −100°C. After 3 min, 4-morpholinocar-

bamoyl chloride (1.42 ml, 12.2 mmol) was added to the

golden-brown solution and the mixture was allowed to

warm to room temperature over 1 h. Workup followed

by column chromatography gave N-morpholino-12,19-

dimethoxypodocarpa-8,11,13-triene (32) (1.41 g, 90%)

as a colourless solid, m.p. 123–124°C. Found: M⁺

401.2565. Calc. for C₂₄H₃₅NO₄: 401.2566. w_max(cm⁻¹):

1

1635 (C=O). H-NMR (l ppm): 1.01 (ddd, J=13.7,

4.0 Hz, H(3ax)); 1.04 (s, H(18)); 1.17 (s, H(20)); 1.20 (s,

H(20)); 1.35–1.50 (m, H(5), H(1ax)); 1.60–1.75 (m,

H(2ax), H(2eq), H(6ax)); 1.88 (bd, J=11.7 Hz,

H(3eq)); 1.97 (bdd, J=13.4, 7.0 Hz, H(6eq)); 2.27 (bd,

J=10.3 Hz, H(1eq)); 2.68–2.90 (m, H(7ax), H(7eq));

3.24 (d, J=9.1 Hz, H(19)); 3.33 (s, 19-OMe); 3.52 (d,

J=9.1 Hz, H(19)); 3.54–3.70 (m, OCH_2(E)); 3.70–3.86

(m, NCH_2(Z), OCH_2(Z)); 3.79 (s, 12-OMe); 3.20–3.34 (b,

NCH_2(E)); 6.76 (s, H(11)); 6.90 (s, H(14). ¹³C-NMR (l

ppm): 18.8(2), C(2); 18.8(9), C(6); 25.2, C(20); 27.4,

C(18); 29.7, C(7); 35.6(5), C(3); 37.7, C(4); 37.9, C(10);

NCH_2(E); 59.4, 19-OMe; 60.0, NCH_2(Z); 67.3, OCH_2(E)

;

67.4, OCH_2(E); 67.9, OCH_2(Z); 75.7, C(19); 76.0, C(19);

106.2, C(11); 106.4, C(11); 120.9(5), C(14); 121.1, C(14);

126.9, C(13); 127.0, C(13); 137.2, C(8); 137.5, C(8);

146.4, C(9); 149.3, C(12); 217.3, CꢀO_cis; 224.0, CꢀO_trans

;

271.6, C_carbene. Mass spectroscopy: m/z 577 [M⁺, 3],

549 (7, M−CO), 521 (7, M−2CO), 465 (75, M−

4CO), 437 (100, M−5CO).

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

215

3.25. Pentacarbonyl[(methylamino)(13-(12-

methoxy-19-norpodocarpa-4(18),8,11,13-tetraene))-

carbene]chromium (34)

3.23. Pentacarbonyl[(morpholino)(13-(12,19-

dimethoxypodocarpa-8,11,13-triene))carbene]chromium

(31): mixed ‘‘anhydride method’’

Butyllithium (0.50 ml, 1.80 mol l⁻¹) was added to a

solution of 6 (0.33 g, 0.906 mmol) in THF (12 ml) at

−78°C. The solution was stirred for 6 min followed by

the addition of hexacarbonylchromium (0.21 g, 0.954

mmol) and the yellow solution was allowed to warm to

room temperature. Tetramethylammonium bromide

(0.147 g, 0.954 mmol) was added, the solvent was

removed in vacuo, and the yellow residue was dissolved

in CH₂Cl₂(12 ml). The ﬂask was covered in foil and the

solution was cooled to −42°C, followed by the addi-

tion of acetyl bromide (70 ml, 0.947 mmol). The bur-

gundy solution was stirred at −42°C for 1 h, then

morpholine (180 ml, 2.06 mmol) was added. The solu-

tion was warmed to room temperature, then reﬂuxed

for 19.5 h. Column chromatography gave pentacar-

bonyl[(morpholino)(13 - (12,19 - dimethoxypodocarpa-

8,11,13-triene))carbene]chromium (31) (0.19 g, 37%) as

a yellow solid.

Methylamine gas (from KOH, 13.1 g, and methyl-

amine hydrochloride, 13.9 g) was condensed into a

solution of 9 (0.623 g, 1.31 mmol) in THF (15 ml) until

the colour changed from red to yellow. Radial chro-

matography (hexanes/ether, 1:1) gave pentacarbonyl-

[(methylamino)(13 - (12 - methoxy - 19 - norpodocarpa - 4

(18),8,11,13-tetraene))-carbene]chromium (34) (0.575 g,

92%) as a yellow oil [E/Z=5:1; the E isomer is a

mixture (1:1) of two rotamers]. Found: M⁺475.1080.

Calc. for C₂₄H₂₅CrNO₆: 475.1087. w_max(cm⁻¹): 2054 (s,

1

CꢀO), 1974 (sh, CꢀO), 1926 (br, CꢀO). H-NMR (l

ppm): 1.00 (s, H(20)_(E)); 1.01 (s, H(20)_(Z)); 1.03 (s,

H(20)_(E)); 1.59 (ddd, J=12.4, 12.4, 4.4 Hz, H(1ax)_(E));

1.69 (ddd, J=12.0, 12.0, 4.4 Hz, H(1ax)_(Z)); 1.70–1.89

(m, H(2ax), H(2eq), H(6ax), H(6eq)); 2.06 (ddd, J=

12.3, 12.3, 4.4 Hz, H(3ax)_(E)); 2.08 (ddd, J=12.3, 12.3,

4.4 Hz, H(3ax)_(Z)); 2.22 (3 lines, H(5), H(1eq)); 2.39, bd,

J=12.0 Hz, H(3eq)); 2.73–2.99 (m, H(7ax), H(7eq));

2.95 (d, J=4.9 Hz, CH_3(E)); 3.70 (d, J=5.1 Hz,

CH_3(Z)); 3.74 (s, 12-OMe_(Z)); 3.78 (s, 12-OMe_(E)); 4.60

(s, H(18)_(E,_Z)); 4.62 (d, J=1.1 Hz, H(18)_(E)); 4.86 (s,

H(18)); 6.38 (s, H(14)_(E)); 6.42 (s, H(14)_(E)); 6.47 (s,

H(14)_(Z)); 6.76 (s, H(11)_(Z)); 6.78 (s, H(11)_(E)); 8.77 (bs,

NH_(Z)); 9.10 (bs, NH_(E)). ¹³C-NMR (l ppm): 21.2(7),

3.24. Pentacarbonyl[(dihydroamino)(13-(12-

methoxy-19-norpodocarpa-4(18),8,11,13-tetraene))-

carbene]chromium (33)

Ammonia gas was condensed into a solution of 9

(0.444 g, 0.932 mmol) in THF (10 ml) until the colour

changed from red to yellow. Radial chromatography

C(6)_(E); 21.3(3), C(6)_(Z); 22.7, C(20)_(E); 22.8(5), C(20)_(Z)

23.6(5), C(2); 29.1, C(7)_(E); 29.3, C(7)_(Z); 36.2(1), C(3)_(E)

;

36.2(8), C(3)_(Z); 37.5, NCH_3(E); 38.4(5), C(1)_(E); 38.4(8),

C(1)_(Z)39.6(1), C(10)_(E)39.6(2), C(10)_(Z)39.7,

;

gave

pentacarbonyl[(dihydroamino)(13-(12-methoxy-

NCH_3(Z); 47.5(6), C(5)_(E); 47.6(5), C(5)_(Z); 47.8, C(5)_(E)

55.1, 12-OMe_(Z); 55.2, 12-OMe_(E); 106.5, C(18)_(E)

106.6(7), C(18)_(Z); 106.7(4), C(18)_(E); 107.3(5), C(11)_(E)

;

19-norpodocarpa-4(18),8,11,13-tetraene))-carbene]chro-

mium (33) (0.390 g, 91%) as a yellow ﬂaky crystals,

m.p. 122–123°C (dec.) (hexanes). Anal. Found: C,

59.97; H, 5.25; N, 2.92. Calc. for C₂₃H₂₃CrNO₆: C,

107.5, C(11)_(E); 107.6, C(11)_(Z); 121.1, C(14)_(E); 121.4,

C(14)_(E)122.3, C(14)_(Z)126.7, C(13)_(Z)127.2(1),

C(13)_(E); 127.2(9), C(13)_(E); 135.4(5), C(8)_(E); 135.6,

C(8)_(Z)146.9(5), C(9)_(Z)147.0, C(9)_(E)147.2(6),

C(12)_(E)147.3(1), C(12)_(E)147.4, C(12)_(Z)150.2,

59.87; H, 5.02; N, 3.04%. Found: M⁺, 461.0934. Calc.

;

for C₂₃H₂₃CrNO₆: 461.0930. w_max(cm⁻¹): 2054 (s,

;

1

CꢀO), 1974 (sh, CꢀO), 1926 (br, CꢀO). H-NMR (l

;

ppm): 1.02 (s, H(20)); 1.62 (ddd, J=12.7, 4.4 Hz,

H(1ax)); 1.68–1.90 (m, H(2ax), H(2eq), H(6ax),

H(6eq)); 2.07 (ddd, J=13.0, 5.4 Hz, H(3ax)); 2.19–2.25

(3 lines, H(5), H(1eq)); 2.39 (ddd, J=13.0, 4.1, 2.4 Hz,

H(3eq)); 2.83–2.89 (4 lines, H(7ax), H(7eq)); 3.81 (s,

12-OMe); 4.62 (d, J=1.4 Hz, H(18)); 4.87 (d, J=1.4

Hz, H(18)); 6.78 (s, H(14)); 6.81 (s, H(11)); 8.64 (bs,

NH_(Z)); 8.94 (bs, NH_(E)). ¹³C-NMR (l ppm): 21.2, C(6);

22.6, C(20); 23.6, C(2); 29.0, C(7); 36.2, C(3); 38.4,

C(1); 39.8, C(10); 47.5, C(5); 55.3, 12-OMe; 106.8,

C(18); 107.9, C(11); 125.5(5), C(14); 127.2, C(13); 138.0,

C(8); 149.6, C(9); 149.7(5), C(12); 150.01, C(4); 217.4,

CꢀO_cis; 233.6, CꢀO_trans; 288.4, C_carbene. Mass spec-

troscopy: m/z (FAB) 461 [M⁺, 8], 433 (17, M−CO),

405 (8, M−2CO), 377 (12, M−3CO), 349 (M−4CO),

321 (M−5CO).

C(4)_(E); 150.4, C(4)_(Z); 217.4, CꢀO_cis; 223.6, CꢀO_trans(E)

;

.

224.2, CꢀO_trans(Z); 280.7, C_carbene(Z); 281.3, C_carbene(E)

Mass spectroscopy: m/z (FAB) 475 [M⁺, 3], 447 (24,

M−CO), 419 (5, M−2CO), 391 (15, M−3CO), 363

(100, M−4CO), 335 (78, M−5CO), 282 (70, 335−

H −Cr).

3.26. Pentacarbonyl[(dimethylamino)(13-(12-

methoxy-19-podocarpa-4(18),8,11,13-tetraene))carbene]-

chromium (35)

Dimethylamine (2.0 ml, 38 mmol) and 9 (0.485 g,

1.02 mmol) in THF (15 ml) were stirred for 1.5 h.

Radial chromatography gave pentacarbonyl[(dimethyl-

amino) (13-(12-methoxy-19-podocarpa-4(18),8,11,13-te-

traene))carbene]chromium (35) (0.429 g, 86%) as a

216

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

yellow oil. w_max(cm⁻¹): 2054 (s, CꢀO), 1976 (sh, CꢀO),

mmol) was added and the solution was stirred for a

further 19.5 h. Radial chromatography gave pentacar-

bonyl[(pyrrolidinyl)(13-(12-methoxy-19-norpodocarpa-

4(18),8,11,13-tetraene))-carbene]chromium (37) (0.455

g, 89%) (7:3 mixture of rotamers) as a pale yellow solid,

1

1929 (br, CꢀO). H-NMR (l ppm): 1.00 (s, H(20)); 1.02

(s, H(20)); 1.50–1.90 (m, H(1ax), H(2ax), H(2eq),

H(6ax), H(6eq)); 2.07 (bdd, J=13.9, 5.3 Hz, H(3ax));

2.17–2.27 (m, H(5), H(1eq)); 2.39 (bd, J=12.4 Hz,

H(3eq)); 2.76–2.88 (m, H(7ax), H(7eq)); 3.08 (s,

NMe_(Z)); 3.74 (s, 12-OMe); 3.95 (s, NMe_(E)); 3.95(5) (s,

NMe_(E)); 4.60 (bs, H(18)); 4.62 (bs, H(18)); 4.86 (bs,

H(18)); 6.33 (s, H(14)); 6.37 (s, H(14)); 6.73 (s, H(11)).

¹³C-NMR (l ppm): 21.3, C(6); 22.8, C(20); 23.7, C(2);

29.3, C(7); 36.2, C(3); 38.5, C(1); 39.6, C(10); 47.6,

C(5); 47.8, C(5); 45.2(5), NCH_3(Z); 45.3, NCH_3(Z); 50.8,

NCH_(E); 55.0, 12-OMe; 106.4, C(18); 106.6(5), C(18);

107.3, C(11); 107.6, C(11); 120.7(5), C(14); 121.0, C(14);

126.9, C(13); 139.3, C(8); 146.4, C(9); 150.3, C(12);

150.5, C(4); 217.5, CꢀO_cis; 223.6, CꢀO_trans; 224.2,

m.p. 122–124°C (hexanes). Found: M⁺, 515.1427.

Calc. for C₂₇H₂₉CrNO₆: 515.1400. w_max(cm⁻¹): 2053

(CꢀO), 1974 (CꢀO), 1926 (CꢀO). ¹H-NMR (l ppm):

0.99 (s, H(20)_maj); 1.02 (s, H(20)_min); 1.64 (ddd, J=12.0,

12.0, 3.8 Hz, H(1ax)); 1.68–1.88 (m, H(2ax), H(2eq),

H(6ax), H(6eq)); 1.95–2.01 (m, CH_2(E)CH₂N); 2.08

(ddd, J=13.1, 13.1, 4.8 Hz, H(3ax)); 2.14–2.25 (m,

H(5), H(1eq), CH_2(Z)CH₂N); 2.38 (bd, J=11.9 Hz,

H(3eq)); 2.75 (bdd, J=16.6, 5.4 Hz, H(7eq)); 2.83 (m,

H(7ax)); 3.22 (ddd, J=13.1, 7.2, 6.7 Hz, CH_ax(E)N);

3.41 (ddd, J=13.1, 6.6, 6.5 Hz, CH_eq(E)N); 3.75 (s,

12-OMe); 4.26 (m, CH_2(Z)N); 4.59 (s, H(18)_maj); 4.61 (s,

H(18)_min); 4.85 (s, H(18)); 6.33 (s, H(14)_maj); 6.37 (s,

H(14)_min); 6.73 (s, H(11)). ¹³C-NMR (l ppm): 21.3(5),

C(6)_maj; 21.3(9), C(6)_min; 22.8(1), C(20)_maj; 22.8(6),

C(20)_min; 23.7, C(2); 25.3(1), CH_2(E)CH₂N; 25.3(6),

CH_2(Z)CH₂N; 29.2, C(7)_maj; 29.4, C(7)_min; 36.2(5),

C(3)_maj; 36.3(2), C(3)_min; 38.5, C(1); 39.5, C(10)_maj; 39.7,

CꢀO_trans; 272.7, C_carbene

.

3.27. Pentacarbonyl[(aziridinyl)(13-(12-

methoxy-19-norpodocarpa-4(18),8,11,13-tetraene))-

carbene]chromium (36)

Aziridine (0.50 ml, 9.7 mmol) and 9 (0.492 g, 1.03

mmol) were stirred in THF (8 ml) at room temperature

for 3.5 h. Radial chromatography (hexanes/ether, 1:1),

gave pentacarbonyl[(aziridinyl)(13 - (12 - methoxy - 19-

norpodocarpa-4(18),8,11,13-tetraene))carbene]chromium

(36) (0.450 g, 89%) as a yellow orange solid, m.p. 120°C

C(10)_min; 47.6, C(5)_maj; 47.9, C(5)_min; 55.1, NCH_2(E)maj

12-OMe; 55.2, NCH_2(E)min58.9, NCH_2(Z)106.4,

C(18)_maj106.7, C(18)_min107.4, C(11)_min107.5,

C(11)_maj; 120.2, C(14)_maj; 120.4, C(14)_min; 127.0(5),

C(13); 140.1, C(8); 146.0(7), C(9); 146.1(2), C(12)_min

,

;

(decomp). Found: M⁺

,

487.1110. Calc. for

146.2, C(12)_maj; 150.3(5), C(4)_min; 150.6, C(4)_maj; 217.8,

CꢀO_cis; 224.2, CꢀO_trans; 267.3, C_carbene. Mass spec-

troscopy: m/z 515 [M⁺, 4], 487 (10, M−CO), 459 (5,

M−2CO), 431 (3, M−3CO), 403 (43, M−4CO), 375

(38, M−5CO).

C₂₅H₂₅CrNO₆: 487.1087. w_max(cm⁻¹): 2054 (s, CꢀO),

1974 (sh, CꢀO), 1926 (br, CꢀO). ¹H-NMR (l ppm):

1.03 (s, H(20)); 1.60 (ddd, J=12.8, 4.6 Hz, H(1ax));

1.68–1.88 (m, H(2ax), H(2eq), H(6ax), H(6eq)); 2.07

(ddd, J=12.9, 5.4 Hz, H(3ax)); 2.22 (dd, J=12.0, 1.0

Hz, H(5)); 2.24 (bd, J=12.8 Hz, H(1eq)); 2.39 (ddd,

J=13.0, 4.0, 2.2 Hz, H(3eq)); 2.58–2.62 (m, NCH_2(E));

2.81–2.84 (4 lines, H(7ax), H(7eq)); 3.21 (dd, J=5.2

Hz, NCH_2(Z)); 3.74 (s, 12-OMe); 4.61 (d, J=1.4 Hz,

H(18)); 4.86 (d, J=1.4 Hz, H(18)); 6.53 (s, H(14)); 6.78

(s, H(11)). ¹³C-NMR (l ppm): 21.1, C(6); 22.7, C(20);

3.29. 12-Methoxy-N-morpholino-19-norpodocarpa-

4(18),8,11,13-tetraene-13-carboxamide (39)

t-Butyllithium (6.6 ml, 1.45 mol l⁻¹, 9.6 mmol) was

added dropwise to a solution of 13 (1.511 g, 4.70 mmol)

in THF (60 ml) cooled to −100°C. After 5 min,

4-morpholinocarbamoyl chloride (1.65 ml, 14.1 mmol)

was added and the mixture was allowed to warm to

room temperature over 1 h. Workup and ﬂash chro-

matography gave 12-methoxy-N-morpholino-19-nor-

podocarpa-4(18),8,11,13-tetraene-13-carboxamide (39)

23.6, C(2); 27.5, NCH_2(Z); 28.7, C(7); 29.1(5); NCH_2(E)

;

36.2, C(3); 38.4, C(1); 39.7, C(10); 47.6, C(5); 55.3,

12-OMe; 106.6, C(18); 107.8, C(11); 123.0(5), C(14);

126.9, C(13); 138.6, C(8); 147.5, C(9); 148.5, C(12);

150.3, C(4); 217.6, CꢀO_cis; 224.2, CꢀO_trans; 270.4,

C_carbene. Mass spectroscopy: m/z 487 [M⁺, 11], 459 (12,

M−CO), 431 (5, M−2CO), 403 (9, M−4CO), 375

(100, M−5CO), 347 (35, 375−CH₂CH₂), 319 (37).

(1.450 g, 87%) as a white foam. Found: M⁺355.2135.

Calc. for C₂₂H₂₉NO₃: 355.2147. w_max(cm⁻¹): 1635

1

(CꢁO). H-NMR (l ppm): 1.28 (s, H(20)); 1.50–1.87

(m, H(1ax), H(2ax), H(2eq), H(6ax), H(6eq)); 2.06

(ddd, J=13.1, 13.1, 5.5 Hz, H(3ax)); 2.16 (bd, J=12.6

Hz, H(5)); 2.24 (bd, J=14.0 Hz, H(1eq)); 2.39 (bd,

J=12.8 Hz, H(3eq)); 2.78–2.84 (H(7ax), H(7eq)); 3.27

(b, NCH_(E)); 3.33 (b, NCH _(E)); 3.55–3.70 (m,

OCH_2(E)); 3.70–3.88 (m, OCH_2(Z); NCH_2(Z)); 4.61 (d,

J=1.2 Hz, H(18)); 4.87 (d, J=1.2 Hz, H(18)); 6.80 (s,

H(11)); 6.96 (s, H(14)). ¹³C-NMR (l ppm): 21.1, C(6);

3.28. Pentacarbonyl[(pyrrolidinyl)(13-(12-

methoxy-19-norpodocarpa-4(18),8,11,13-tetraene))-

carbene]chromium (37)

A solution of 9 ( 0.474 g, 0.995 mmol) and pyrro-

lidine (0.30 ml, 3.6 mmol) in THF (8 ml) was stirred at

room temperature for 3.5 h. Pyrrolidine (0.3 ml, 3.6

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

217

22.6, C(20); 23.5, C(2); 28.9, C(7); 36.1, C(3); 38.3,

C(1), 39.7(5), C(10); 42.1, NCH_2(Z); 47.3, NCH_2(E); 47.6,

C(5); 55.5, 12-OMe; 66.8, OCH_2(E); 69.0, OCH_2(Z)

3.31. 12-Methoxy-19-norpodocarpa-

4(18),8,11,13-tetraen-13-oic acid (41)

;

106.7, C(18); 107.8, C(11); 122.8, C(14); 127.8, C(13);

128.7, C(8); 149.7, C(9); 150.0, C(12); 153.2, C(4),

168.1, CꢁO. Mass spectroscopy: m/z 355 [M⁺, 22], 340

Butyllithium (1.4 ml, 2.5 mol l⁻¹) was added to a

solution of 13 (1.125 g, 3.93 mmol) in THF (15 ml)

cooled to −78°C. After 3 min solid carbon dioxide

(ꢀ3 g) was added. Workup and ﬂash chromatography

(Et₂O) gave 12-methoxy-19-norpodocarpa-4(18),8,11,

13-tetraen-13-oic acid (41) (0.734 g, 73%) as a white

(2, M−Me ), 269 (100, M−C₄H₈NO ).

3.30. Pentacarbonyl[(morpholino)(13-(12-

methoxy-19-norpodocarpa-4(18),8,11,13-tetraene))-

carbene]chromium (38)

foam. Found: M⁺286.1572. Calc. for C₁₈H₂₂O₃:

286.1569. w_max(cm⁻¹): 3284 (br, OH), 1734 (s, CꢁO),

1

1645 (s, CꢁC_alkene), 1612 (s, CꢁC_aromatic). H-NMR (l

A solution of sodium naphthalenide (from sodium,

0.401 g, and naphthalene, 1.388 g) in THF (10 ml) was

added to Cr(CO)₆(1.092 g, 4.96 mmol) in THF (10 ml)

at −78°C; the mixture was warmed to 0°C, and stirred

for 30 min. The red-orange solution of Na₂Cr(CO)₅was

cooled to −78°C and 39 (1.076 g, 3.03 mmol) in THF

(8 ml) was added rapidly. After 40 min the solution was

warmed to 0°C for 30 min, then cooled to −78°C,

followed by the addition of Me₃SiCl (1.3 ml, 10.3

mmol). After 1 h, alumina (14 g) was added and the

yellow slurry was warmed to room temperature. Flash

chromatography (hexanes/ether, 1:1) gave pentacar-

bonyl[(morpholino)(13-(12-methoxy-19-norpodocarpa-

4(18),8,11,13-tetraene))carbene]chromium (38) (1.244

ppm): 1.03 (s, H(20)); 1.61 (ddd, J=12.9, 12.9, 4.5 Hz,

H(1ax)); 1.69–1.91 (m, H(2ax), H(2eq), H(6ax),

H(6eq)); 2.07 (ddd, J=13.1, 13.1, 5.5 Hz, H(3ax)); 2.20

(bd, J=12.1 Hz, H(5)); 2.25 (bd, J=12.7 Hz, H(1eq));

2.40 (ddd, J=13.1, 4.2, 2.3 Hz, H(3eq)); 2.85 (ddd,

J=17.1, 11.3, 7.0 Hz, H(7ax)); 2.93 (ddd, J=17.1, 6.3,

1.5 Hz, H(7eq)); 4.03 (s, 12-OMe); 4.63 (d, J=1.5 Hz,

H(18)); 4.89 (d, J=1.5 Hz, H(18)); 6.95 (s, H(11)); 7.90

(s, H(14)); 10.80 (b, COOH). ¹³C-NMR (l ppm):

20.9(5), C(6); 22.6, C(20); 23.4, C(2); 28.7, C(7); 36.0,

C(3); 38.2, C(1); 40.2, C(10); 47.2, C(5); 56.5, 12-OMe;

107.2, C(18); 108.4, C(11); 114.9, C(13); 129.4, C(8);

134.4, C(14); 149.4, C(9); 155.1, C(12); 156.0, C(4);

165.5, COOH. Mass spectroscopy: m/z 286 [M⁺, 100],

g, 77%) as a yellow foam. Found: M⁺531.1371. Calc.

271 (19, M−Me ), 227 (27, 271−CO₂), 212 (24, 227−

for C₂₇H₂₉CrNO₇: 531.1349. w_max(cm⁻¹): 2052 (s,

Me ), 195 (22, M−MeO −Me −CO₂H ).

1

CꢀO), 1972 (sh, CꢀO), 1916 (br, CꢀO). H-NMR (l

ppm): 1.00 (s, H(20)); 1.03 (s, H(20)); 1.50–1.90 (m,

H(1ax), H(2ax), H(2eq), H(6ax), H(6eq)); 2.06 (ddd,

J=13.0, 13.0, 5.3 Hz, H(3ax)); 2.10 (ddd, J=12.9,

12.9, 5.1 Hz, H(3ax)); 2.18 (dd, J=11.9, 3.1 Hz, H(5));

2.18–2.28 (m, H(1eq), H(5)); 2.39 (bd, J=12.6 Hz,

H(3eq)); 2.70–2.91 (m, H(7ax), H(7eq)); 3.44–3.58 (m,

NCH_(E)); 3.57–3.67 (m, NCH_(E), OCH_2(E)); 3.75 (s,

12-OMe); 3.98–4.04 (m, OCH_ax(Z)); 4.06–4.11 (m,

OCH_eq(Z)); 4.37–4.44 (m, NCH_ax(Z)); 4.60 (d, J=1.2

Hz, H(18)); 4.62 (d, J=1.2 Hz, H(18)); 4.67–4.72 (m,

NCH_eq(Z)); 4.86 (d, J=1.5 Hz, H(18)); 6.35 (s, H(14));

6.40 (s, H(14)); 6.72(5) (s, H(11)); 6.73(3) (H(11)). ¹³C-

NMR (l ppm): 21.2(6), C(6); 21.3(2), C(6); 22.8, C(20);

23.6(5), C(2); 29.1, C(7); 29.3, C(7); 36.2, C(3); 36.3,

C(3); 38.4(6), C(1); 38.5(3), C(1); 39.5, C(10); 39.7,

3.32. 12-Methoxy-19-norpodocarpa-4(18),

8,11,13-tetraen-13-oyl chloride (42)

A solution of thionyl chloride (10 ml, 0.14 mol) and

41 (0.662 g, 2.31 mmol) was stirred at room tempera-

ture for 2 h. Removal of excess thionyl chloride gave

12-methoxy-19-norpodocarpa-4(18),8,11,13-tetraen-13-

oyl chloride (42) (0.701 g, 100%) as a pale brown foam.

w_max(cm⁻¹): 1769 (CꢁO).

3.33. 12-Methoxy-N-(trans-2,6-dimethylmorpholino)-

19-norpodocarpa-4(18),8,11,13-tetraen-13-carboxamide

(43)

trans-2,6-Dimethylmorpholine [40] (0.270 g, 2.34

mmol) was added to a solution of 42 (0.701 g, 2.31

mmol), triethylamine (0.40 ml, 2.9 mmol), and N,N-

dimethylaminopyridine (17 mg, 0.14 mmol) in

dichloromethane (20 ml). The solution was stirred at

room temperature for 16.5 h, then washed with water,

and dried (MgSO₄). Column chromatography (Et₂O)

C(10); 47.5, C(5); 47.8, C(5); 55.0, 12-OMe, NCH_2(E)

;

60.0, NCH_2(Z); 67.3(3), OCH_2(E); 67.3(9), OCH_2(E); 67.9,

OCH_2(Z); 106.5, C(11); 106.8, C(11); 107.1, C(18);

107.3, C(18); 121.1, C(14); 121.4, C(14); 127.0(1), C(13);

127.0(8), C(13); 137.4, C(8); 137.8, C(8); 146.4, C(9);

146.5(8), C(12); 146.6(3), C(12); 150.2, C(4); 150.4,

C(4); 217.3(0), CꢀO_cis; 217.3(3), CꢀO_cis; 223.9(6),

CꢀO_trans; 223.9(9), CꢀO_trans; 271.6, C_carbene. Mass spec-

troscopy: m/z 531 [M⁺, 4], 503 (13, M−CO), 475 (12,

M−2CO), 447 (4, M−3CO), 419 (98, M−4CO), 391

gave

12-methoxy-N-(trans-2,6-dimethylmorpholino)-

19 - norpodocarpa - 4(18),8,11,13 - tetraene - 13 - carboxa-

mide (43) (0.439 g, 49%) as a colourless oil. Found M⁺

383.2449. Calc. for C₂₄H₃₃NO₃: 383.2460. w_max(cm⁻¹):

1

(100, M−5CO), 376 (8, 391−Me ), 356 (37), 340 (21),

1636 (CꢁO). H-NMR (l ppm): 1.02 (bs, H(20)); 1.10

269 (30).

(b, O_ECHCH₃); 1.11 (b, O_ECHCH₃); 1.28 (b,

218

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

O_ZCHCH₃); 1.60–1.90 (m, H(1eq), H(2ax), H(2eq),

H(6ax), H(6eq)); 2.03–2.40 (m, H(1eq), H(3ax), H(3eq),

H(5)); 2.73–3.00 (m, H(7ax), H(7eq)); 3.30–3.40 (m,

N_ECH_ax)); 3.50–3.61 (m, N_ZCH_ax)); 3.78 (s, 12-OMe);

3.79 (s, 12-OMe); 3.71–4.00 (m, OCHCH₃, N_ECH_eq));

4.05–4.17 (b, N_ZCH_eq); 4.61 (d, H(18)); 4.86 (H(18));

6.72 (s, H(11)); 6.79 (s, H(11)); 6.80 (s, H(11)); 6.84 (s,

H(11)); 6.90 (b, H(14)); 6.93 (b, H(14)). ¹³C-NMR (l

ppm): 17.3, O_ECHCH₃; 17.5, O_ZCHCH₃; 20.8, C(6);

21.2, C(6); 22.7, C(20); 23.6, C(2); 29.1, C(7); 36.2,

C(3); 37.8, C(1); 38.4, C(1); 40.3, C(10); 46.3, C(5);

47.6, C(5); 51.6, N_ECH₂;52.0, N_ECH₂; 52.9, N_ZCH;

55.6, 12-OMe; 65.8, OCH; 66.4, OCH; 106.8, C(18);

106.9, C(18); 107.9, C(11); 123.0, C(14); 127.8, C(13);

128.7, C(8); 149.7, C(9); 150.8, C(12); 153.3, C(4);

169.0, CꢁO. Mass spectroscopy: m/z 383 [M⁺, 22], 368

6.72 (s, H(11)); 6.73 (s, H(11)); 6.76 (s, H(11)). ¹³C-

NMR (l ppm): 17.1, O_ECHCH₃; 17.4, O_ZCHCH₃;

17.5, O_ZCHCH₃; 21.2(6), C(6); 21.3(4), C(6); 21.4(9),

C(6); 22.7(5), C(20); 22.9, C(20); 23.2, C(20); 23.7, C(2);

24.2, C(2); 29.1, C(7); 29.3, C(7); 30.8, C(7); 36.2, C(3);

36.3, C(3); 38.0, C(1); 38.4(6), C(1); 38.5, C(1); 39.5,

C(10); 39.7, C(10); 47.5, C(5); 47.8, C(5); 54.6, 12-OMe;

55.0, 12-OMe; 58.3, N_ECH₂; 58.3(6), N_ECH₂; 63.3(7),

N_ZCH₂; 63.4(5), N_ZCH₂; 64.0(8), N_ZCH₂; 66.7(5),

OCHCH₃; 67.0, OCHCH₃; 67.2, OCHCH₃; 106.0,

C(18); 106.5, C(18); 106.7, C(18); 107.1, C(11); 107.2,

C(11); 107.3, C(11); 107.9, C(11); 120.5, C(14); 120.8,

C(14); 121.0, C(14); 121.1, C(14); 121.2, C(14); 121.4,

C(14); 121.8, C(14); 122.0, C(14); 125.0, C(13); 125.1,

C(13); 126.9, C(8); 127.0, C(8); 146.2, C(12); 146.5,

C(12); 147.1, C(12); 150.2, C(4); 150.4, C(4); 217.3(0),

CꢀO_cis; 217.3(2), CꢀO_cis; 217.4(1), CꢀO_cis; 217.5,

(30, M−Me ), 283 (20), 270 (18), 269 (100, M−

C₅H₈NO₂).

CꢀO_cis; 223.8, CꢀO_trans; 223.9, CꢀO_trans; 272.1, C_carbene;

272.2, C_carbene; 272.3, C_carbene. Mass spectroscopy: m/z

559 [M⁺, 4], 531 (12, M−CO), 503 (10, M−2CO),

447 (92, M−4CO), 419 (100, M−5CO).

3.34. Pentacarbonyl[(trans-2,6-dimethylmorpolino)-

(13-(12-methoxy-19-norpodocarpa-4(18),

8,11,13-tetraene)carbene]chromium (40)

3.35. 12,19-Dimethoxypodocarpa-8,11,13-trien-13-oic

acid (45)

A solution of sodium naphthalenide (from sodium,

0.334 g, and naphthalene, 0.544 g) was added to

Cr(CO)₆(0.428 g, 1.94 mmol) in THF (10 ml) at

−78°C, then warmed to room temperature. The solu-

tion of Na₂Cr(CO)₅was cooled to −78°C and a solu-

tion of 43 (0.493 g, 1.29 mmol) in THF (10 ml) was

added. After 30 min the solution was warmed to 0°C

for 45 min, then cooled to −78°C and chlorotrimethyl-

silane (0.50 ml, 3.95 mmol) was added. After 75 min,

alumina (1 g) was added and alumina and the suspen-

sion was warmed to room temperature. Column chro-

matography (hexanes/ether, 1:1) gave pentacarbonyl-

[(trans - 2,6 - dimethylmorpholino)(13 - (12 - methoxy - 19-

norpodocarpa - 4(18),8,11,13 - tetraene))carbene]chro-

mium (40) (0.394 g, 57%) as a yellow foam. Found:

M^+.559.1668. Calc. for C₂₉H₃₃CrNO₇: 559.1662. w_max

(cm⁻¹): 2052 (s, CꢀO), 1971 (sh, CꢀO), 1916 (br, CꢀO).

¹H-NMR (l ppm): 1.00 (s, H(20)); 1.02 (s, H(20)); 1.04

(s, H(20)); 1.09(6) (d, J=5.4 Hz, O_ECHCH₃); 1.09(9)

(d, J=5.8 Hz, O_ECHCH₃); 1.10(4) (d, J=5.8 Hz,

O_ECHCH₃); 1.38 (d, J=6.2 Hz, O_ZCHCH₃); 1.39 (d,

J=6.4 Hz, O_ZCHCH₃); 1.50–1.85 (m, H(1eq), H(2ax),

H(2eq), H(6ax), H(6eq)); 1.94–2.28 (m, H(1eq), H(3ax),

H(5)); 2.39 (d, J=12.9 Hz, H(3eq)); 2.68–2.92 (m,

H(7ax), H(7eq)); 3.18–3.36 (m, N_ECH_ax)); 3.48–3.60

(m, N_ZCH_ax)); 3.74(0) (12-OMe); 3.74(5) (12-OMe);

3.74(8) (12-OMe); 3.89–3.99 (m, N_ZCH_ax); 4.03–4.08

(m, N_ECH_eq); 4.15–4.22 (m, OCHCH₃); 4.28–4.36 (m,

OCHCH₃); 4.56–4.62 (bd, J=10.4 Hz, N_ZCH_eq); 4.66

(bs, H(18)); 4.69 (bs, H(18)); 4.86 (d, J=1.6 Hz,

H(18)); 6.23 (s, H(14)); 6.26 (s, H(14)); 6.28 (s, H(14));

6.30 (s, H(14)); 6.34 (s, H(14)); 6.37 (s, H(14)); 6.38 (s,

H(14)); 6.41 (s, H(14)); 6.42 (s, H(14)); 6.70 (s, H(11));

Butyllithium (0.94 ml, 2.5 mol l⁻¹) was added to a

solution

of

13-bromo-12,19-dimethoxypodocarpa-

8,11,13-triene (6) (0.856 g, 2.33 mmol) in THF (10 ml)

at −78°C. After 5 min. solid carbon dioxide (ꢀ5 g)

was added. Workup and column chromatography gave

12,19-dimethoxypodocarpa-8,11,13-trien-13-oic

acid

(45) (0.584 g, 75%) as a white foam. Found: M⁺

332.1986. Calc. for C₂₀H₂₈O₄: 332.1988. w_max(cm⁻¹):

1

3292 (br, OH), 1735 (s, CꢁO), 1107 (CꢂOꢂC). H-NMR

(l ppm): 1.03 (ddd, J=13.6, 4.2 Hz, H(3ax)); 1.05 (s,

H(18)); 1.21 (s, H(20)); 1.40 (dd, J=12.8, 2.0 Hz,

H(5)); 1.46 (ddd, J=12.9, 3.8 Hz, H(1ax)); 1.61−1.81

(m, H(2ax), H(2eq), H(6ax)); 1.89 (bdd, J=13.5, 1.1

Hz, H(3eq)); 2.01 (ddt, J=13.5, 7.4, 1.8 Hz, H(6eq));

2.28 (bd, J=13.0 Hz, H(1eq)); 2.79 (ddd, J=16.9,

11.5, 7.2 Hz, H(7ax)); 2.93 (bdd, J=16.9, 6.1 Hz,

H(7eq)); 3.26 (d, J=9.1 Hz, H(19)); 3.33 (s, 19-OMe);

3.51 (d, J=9.1 Hz, H(19)); 4.03 (s, 12-OMe); 6.91 (s,

H(11)); 7.84 (s, H(14)); 10.82 (bs, COOH). ¹³C-NMR (l

ppm): 19.0, C(2); 19.1, C(6); 25.4, C(20); 27.6, C(18);

29.7, C(7); 35.8, C(3); 38.0, C(10); 38.6, C(4); 38.9,

C(1); 50.7, C(5); 56.5, 12-OMe; 59.4, 19-OMe; 75.8,

C(19); 107.6, C(11); 114.7, C(13); 129.3, C(8); 134.2,

C(14); 155.0, C(9); 157.6, C(12); 165.5, COOH. Mass

spectroscopy: m/z 332 [M⁺, 95], 205 (100).

3.36. 12,19-Dimethoxypodocarpa-8,11,13-triene-13-oyl

chloride (46)

A solution of 45 (0.312 g, 0.939 mmol) and thionyl

chloride (2 ml) was heated to 50°C for 30 min. Removal

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

219

dimethoxypodocarpa-8,11,13-triene))carbene]chromium

(44) (0.147 g, 52%) as a yellow foam. Found: M^+.

605.2086. Calc. for C₃₁H₃₉CrNO₈: 605.2081. w_max

(cm⁻¹): 2051 (s, CꢀO), 1971 (sh, CꢀO), 1916 (br, CꢀO).

¹H-NMR (l ppm): 1.00 (m, H(3ax)); 1.04 (s, H(18));

1.05 (s, H(18)); 1.07 (d, J=4.7 Hz, O_ECHCH₃); 1.09

(d, J=5.0 Hz, O_ECHCH₃); 1.18 (s, H(20)); 1.20 (s,

H(20)); 1.38 (d, J=6.4 Hz, O_ZCHCH₃); 1.39 (d, J=

6.4 Hz, O_ZCHCH₃); 1.41–1.49 (m, H(1ax), H(5));

1.60–1.80 (m, H(2ax), H(2eq), H(6ax)); 1.86 (bd, J=

12.3 Hz, H(3eq)); 1.89 (d, J=12.3 Hz, H(3eq)); 1.93–

2.02 (m, H(6eq)); 2.24 (bd, J=12.0 Hz, H(1eq)); 2.27

(bd, J=12.0 Hz, H(1eq)); 2.60–2.91 (m, H(7ax),

H(7eq)); 3.21–3.27 (m, H(19)); 3.33 (s, 19-OMe); 3.34

(s, 19-OMe); 3.49–3.57 (m, H(19), N_ECH_ax)); 3.71 (s,

12-OMe); 3.73 (s, 12-OMe); 3.89–4.01 (m, N_ZCH_ax));

4.01–4.10 (bdd, J=13.0, 6.9 Hz, N_ECH_eq)); 4.27–4.36

(m, OCHCH₃)); 4.57–4.69 (m, N_ZCH_eq)); 6.22 (s,

H(14)); 6.25 (s, H(14)); 6.32 (s, H(14)); 6.35 (s, H(14));

6.69 (bs, H(11)). ¹³C-NMR (l ppm): 17.0(5),

O_ECHCH₃; 17.1, O_ECHCH₃; 17.2, O_ECHCH₃; 17.4,

O_ZCHCH₃; 17.5, O_ZCHCH₃; 19.1, C(2); 19.3, C(6);

25.6, C(20); 25.7, C(20); 27.5, C(18); 27.6, C(18); 30.3,

C(7); 30.4, C(7); 35.8(7), C(3); 35.9(3), C(3); 37.9,

C(10); 38.0, C(10), C(4); 38.2, C(4); 39.0, C(1); 51.0,

C(5); 51.1, C(5); 51.3, C(5); 54.5, 12-OMe; 55.0, 12-

OMe; 58.2, N_ECH₂; 58.3, N_ECH₂; 58.4, N_ECH₂; 59.4,

19-OMe; 63.3, N_ZCH₂; 63.4, N_ZCH₂; 64.0, N_ZCH₂;

64.1, N_ZCH₂; 66.7, O_ECHCH₃; 66.9, O_ECHCH₃; 67.1,

O_ZCHCH₃; 75.6, C(19); 75.9, C(19); 106.2, C(11);

106.3, C(11); 106.4, C(11); 120.3, C(14); 120.4, C(14);

121.6, C(14); 121.7, C(14); 126.7(5), C(13); 126.8(4),

C(13); 137.4, C(8); 137.6, C(8); 137.9, C(8); 146.1(9),

C(9); 146.2(3), C(9); 146.7, C(9); 149.1(5); 149.1(8),

C(12); 217.2(7), CꢀO_cis; 217.2(9), CꢀO_cis; 217.3(9),

CꢀO_cis; 217.4(2), CꢀO_cis; 223.8(7), CꢀO_trans; 223.9(3),

of excess thionyl chloride gave 12,19-dimethoxypodo-

carpa-8,11,13-trien-13-oyl chloride (46) as a white foam

(0.319 g, 100%). w_max(cm⁻¹) 1770 (CꢁO).

3.37. 12,19-Dimethoxy-N-(trans-2,6-dimethylmor-

pholino)podocarpa-8,11,13-triene-13-carboxamide (47)

trans-2,6-Dimethylmorpholine (0.115 g, 0.998 mmol)

was added to a solution of 46 (0.319 g, 0.939 mmol)

and triethylamine (0.15 ml, 1.08 mmol) in

dichloromethane (10 ml). After 14 h at room tempera-

ture, workup and column chromatography (Et₂O) gave

12,19 - dimethoxy - N - (trans - 2,6 - dimethylmorpholino)-

podocarpa-8,11,13-triene-13-carboxamide (47) (0.384 g,

95%). Found M⁺429.2874. Calc. for C₂₆H₃₉NO₄:

1

429.2879. w_max(cm⁻¹): 1635 (CꢁO). H-NMR (l ppm):

1.01 (ddd, J=13.8, 13.8, 4.2 Hz, H(3ax)); 1.04 (s,

H(18)); 1.10 (b, O_ECHCH₃); 1.11 (b, O_ECHCH₃); 1.17

(bs, H(20)); 1.25–1.33 (m, O_ZCHCH₃); 1.39–1.45 (m,

H(1ax), H(5)); 1.60–1.80 (m, H(2ax), H(2eq), H(6eq));

1.88 (bd, J=12.0 Hz, H(3eq)); 1.96 (d, J=13.3 Hz,

H(6eq)); 1.98 (d, J=13.3 Hz, H(6eq)); 2.27 (bd, J=

11.0 Hz, H(1eq)); 2.68–2.97 (m, H(7ax), H(7eq)); 3.24

(d, J=9.1 Hz, H(19)); 3.33 (s, 19-OMe); 3.52 (d, J=

9.1 Hz, H(19)); 3.50–3.63 (m, N_ECH_ax); 3.78 (s, 12-

OMe); 3.67–4.10 (m, N_ZCH_ax, N_ZCH_eq, OCHCH₃,

N_ECH_eq); 6.76 (s, H(11)); 6.87 (bs, H(14)). ¹³C-NMR (l

ppm): 17.2, O_ECHCH₃; 17.5, O_ZCHCH₃; 19.1, C(2);

19.2, C(6); 25.5, C(20); 27.6, C(18); 30.1, C(7); 30.9,

C(7); 35.9, C(3); 38.0, C(10); 38.2, C(4); 39.0, C(1);

46.3, C(5); 51.2, N_ECH₂; 55.5, 12-OMe; 59.4, 19-OMe;

65.8, N_ZCH₂; 66.5, OCHCH₃; 75.9, C(19); 76.0, C(19);

107.1, C(11); 122.7, C(14); 123.0, C(14); 127.8, C(13);

128.5, C(13); 137.4, C(8); 152.3, C(9); 153.3, C(12);

CꢁO not observed, very broad. Mass spectroscopy: m/z

429 [M⁺, 30], 315 (100, M−C₅H₈NO₃).

CꢀO_trans

; 224.0, CꢀO_trans; 224.1, CꢀO_trans; 272.0,

C_carbene; 272.2, C_carbene; 273.9(5), C_carbene; 274.1, C_carbene

.

Mass spectroscopy: m/z 605 [M⁺, 5], 577 (10,

M−CO), 549 (7, M−2CO), 493 (75, M−4CO), 465

(100, M−5CO); 450 (8, 465−Me^.), 414 (20, 465+

3.38. Pentacarbonyl[(trans-2,6-dimethylmorpholino)-

(13-(12,19-dimethoxypodocarpa-8,11,13-triene))carbene]-

chromium (44)

H −Cr).

A solution of sodium naphthalenide (from sodium,

0.2 g, and naphthalene, 0.2 g) in THF (5 ml) was added

to Cr(CO)₆(0.154 g, 0.700 mmol) in THF (5 ml) at

−78°C; the mixture was then warmed to 0°C. The

solution of Na₂Cr(CO)₅was cooled to −78°C and 47

(0.200 g) in THF (7 ml) was added. After 30 min, the

solution was warmed to 0°C for 30 min, then cooled to

−78°C and chlorotrimethylsilane (0.2 ml, 1.58 mmol)

was added. After 1.5 h alumina (8 g) was added, and

the yellow-orange slurry was warmed to room tempera-

ture. Chromatography (hexanes/ether, 1:1) gave pen-

tacarbonyl[(trans - 2,6 - dimethylmorpholino)(13 - (12,19-

4. Supplementary material

Crystallographic data for the structural analysis have

been deposited with the Cambridge Crystallographic

Data Centre, CCDC nos. 154562 for 12, 154563 for 31,

and 154564 for 33. Copies of this information 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 http://

www.ccdc.cam.ac.uk).

220

P.D. Woodgate et al. / Journal of Organometallic Chemistry 626 (2001) 199–220

[22] B.E. Mann, B.F. Taylor, ¹³C-NMR Data for Organometallic

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Synthesis of chromium aminocarbene complexes of diterpenoids

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