Optically active phospholes: Synthesis and use as chiral precursors for phosphinidene and phosphaferrocene complexes

Article abstract of DOI:10.1002/1099-0682(200207)2002:7<1657::AID-EJIC1657>3.0.CO;2-W

Phospholes bearing chiral menthyl, myrtanyl, and (4-isopropyloxazolino)phenyl groups at the phosphorus atom were prepared. They were used as precursors for 7-phosphanorbornadienes and phosphinidene complexes. Unexpectedly, the [(4-isopropyloxazolino)pheny

Full text of DOI:10.1002/1099-0682(200207)2002:7<1657::AID-EJIC1657>3.0.CO;2-W

FULL PAPER
Optically Active Phospholes: Synthesis and Use as Chiral Precursors for
Phosphinidene and Phosphaferrocene Complexes
Xavier Sava,[a] Angela Marinetti,*[b] Louis Ricard,[a] and Francois Mathey*[a]
¸
Keywords: Phosphorus heterocycles / Asymmetric catalysis / P ligands / Phosphinidene complexes / Chiral phospholes /
Phosphaferrocenes
Phospholes bearing chiral menthyl, myrtanyl, and (4-isoprop-
general approach to 7-aza-1-phosphanorbornadiene and
yloxazolino)phenyl groups at the phosphorus atom were pre- norbornene derivatives. The (4-isopropyloxazolino)phenyl-
pared. They were used as precursors for 7-phosphanorborna-
dienes and phosphinidene complexes. Unexpectedly, the [(4-
isopropyloxazolino)phenyl]phosphinidene gave an intramo-
lecular adduct with the imine moiety, which behaved as a
1,3-dipole in cycloaddition reactions. This afforded a new,
substituted phosphole was also used for the synthesis of new
chiral phosphaferrocene complexes bearing oxazoline moiet-
ies.
( Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany,
2002)
Introduction
According to an analogous strategy, i.e. taking advantage
from the reactivity of nonracemic phospholes to prepare
chiral phosphanes with nonconventional structures and po-
tential interest in catalysis, we started the work presented
herein. This includes the synthesis of some new chiral phos-
pholes and their use as precursors for phosphirenes, phos-
phaferrocenes, and new azaphosphanorbornadiene derivat-
ives.
The organic chemistry of phospholes is extremely rich
and varied, as has been shown by the work of many groups
during the last decades.[1] Besides simple modifications of
the phosphole ring substituents, three main transformations
giving access to other classes of phosphorus derivatives are
known: these are [4ϩ2] cycloaddition reactions at the dienic
system, which afford 7-phosphanorbornenes[2,3] or 7-phos-
phanorbornadiene[4] derivatives; [1,5] sigmatropic shifts of
the aryl, vinyl, or other labile phosphorus substituents
around the phosphole nucleus, which lead to 1-phos-
phanorbornadienes;[5] and finally, the reactivity of either
phospholes themselves or phospholyl anions towards suit-
able transition metal derivatives, which affords an easy ac-
cess to phosphacyclopentadienyl complexes and phos-
phametallocenes.[6,7]
Despite the wide synthetic potential of phosphole chem-
istry, the use of chiral species as synthetic tools has barely
been considered. A few optically active phospholes, mainly
dibenzophosphole derivatives, have been applied as chiral
auxiliaries in transition metal promoted reactions.[8] Recent
reports from T. Hayashi disclose the synthesis of enantiom-
erically pure 2,5-dimenthyl-1-phenylphosphole and its use
for the preparation of phosphaferrocene, phosphacyman-
trene, and diphosphole derivatives.[9]
Results and Discussion
Synthesis of Chiral Phospholes
Chirality in phospholes could be provided by optically
pure substituents on either the carbon or the phosphorus
atoms. The phosphole ring itself has a low phosphorus in-
version barrier (ca. 16 kcal/mol), so it racemizes at room
temperature. From a synthetic point of view, the most at-
tractive compounds seem to be phospholes bearing a chiral
group on the phosphorus atom, whose easy preparation
from phospholyl anions and chiral electrophiles contrasts
with the restricted availability of optically active diene moi-
eties.
In this work, two kinds of chiral auxiliaries were consid-
ered as phosphorus substituents: alkyl groups derived from
chiral pool terpene alcohols (menthol and myrtanol), and
valine-derived phenyloxazoline moieties. Both terpene alco-
hols and amino acids can be conveniently used as stoichi-
ometric chiral auxiliaries because of their large-scale avail-
ability.
[a]
´ ´ ´ ´
Laboratoire Heteroelements et Coordination, Ecole
Polytechnique
91128 Palaiseau Cedex, France
[b]
`
´
Laboratoire de Synthese Selective Organique et Produits
Naturels, ENSCP
Chiral phospholes are obtained from 3,4-dimethyl-1-
phenylphosphole (1)[10] via the corresponding phospholyl
anion by substitution on the phosphorus atom, as shown
11, rue Pierre et Marie Curie, 75231 Paris Cedex, France
Fax: (internat.) ϩ 33-1/44071062
E-mail: marinet@ext.jussieu.fr
Eur. J. Inorg. Chem. 2002, 1657Ϫ1665  WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 1434Ϫ1948/02/0707Ϫ1657 $ 20.00ϩ.50/0
1657

X. Sava, A. Marinetti, L. Ricard, F. Mathey
FULL PAPER
in Scheme 1. After cleavage of the phosphorusϪphenyl Synthesis of (7-Phosphanorbornadiene)W(CO)5 Complexes
bond of 1 with lithium, the phospholyl anion 2 gives nucle- ؊ Generation of Chiral Phosphinidenes
ophilic substitution reaction on the mesylate of (Ϫ)-men-
thol to afford the P-neomenthyl-substituted phosphole 3a.
(7-Phosphanorbornadiene)W(CO)5 complexes are easily
accessible from the corresponding phosphole complexes by
DielsϪAlder cycloadditions with activated alkynes.[4] These
compounds were mainly used as synthetic precursors for
terminal phosphinidene complexes, which are highly react-
ive intermediates with carbene-like behavior.[14,15] For in-
stance, addition of (phosphinidene)M(CO)5 complexes to
olefins and alkynes leads to the corresponding phosphirane
and phosphirene complexes, respectively. When the phos-
phinidene phosphorus atom bears an optically pure sub-
stituent, chiral induction can be expected in its addition to
unsymmetrical olefins and acetylenes. To verify this theory,
we examined the preparation of the 7-phosphanorbornadi-
ene complexes 5, as well as their thermolysis and the sub-
sequent phosphinidene trapping reactions, as shown in
Schemes 3 and 4.
Scheme 1. Synthesis of chiral phospholes
The analogous reaction between the phospholyl anion
and the mesylate of (1S)-myrtanol[11,12] afforded the corres-
ponding, highly air-sensitive P-myrtanylphosphole com-
pound. It was isolated only as its W(CO)5 complex 4b.
Reaction of 2 with the (Ϫ)-(S)-2-(2-fluorophenyl)-4-isop-
ropyloxazoline gave the air-stable phosphole 3c in good
yield (61%). The (fluorophenyl)oxazoline has already been
used as an electrophile in the analogous P-arylation of a
dibenzophospholyl anion.[8e]
Scheme 3. Generation of phosphinidene complexes
The optically active phospholes 3a and 3c provide new
chiral ligands for transition metal promoted asymmetric
catalysis. Their potential applications are likely to be those
where other phospholes have already been used success-
fully: for example hydroformylation, hydrogenation, and
carbonylation reactions. Moreover, phosphole 3c should
find applications in a number of catalytic reactions usually
promoted by phosphanyloxazoline ligands.[13] As a very
preliminary test, we checked the effectiveness of phosphole
3c as chiral ligand in the palladium-catalyzed substitution
of 1,3-diphenylpropenyl acetate with sodium malonate un-
der standard conditions. As expected, the observed catalytic
activity, as well as the enantioselectivity, is quite satisfact-
ory (Scheme 2).
Scheme 4. Trapping reactions of transient phosphinidene com-
plexes
The phosphole complexes 4aϪc could be obtained by tre-
ating the preformed phospholes 3 with the (THF)W(CO)5
complex. For the air-sensitive phosphole 3b, the most con-
venient procedure[16] included complexation of the phos-
pholyl anion, followed by reaction of the phospholyl-
tungsten complex with myrtanyl mesylate to give 4b (see
Exp. Sect.).
Scheme 2. Palladium-catalyzed allylic substitution
The course of the reaction between 4 and DMAD was
Exhaustive catalytic screening of phospholes 3 lies bey- largely dependent on the nature of the phosphorus substitu-
ond the scope of this work and will be reported later. In- ent R*. When R* ϭ neomenthyl, the DielsϪAlder cycload-
deed, the main purpose of this work was to check the use dition was prevented by the steric hindrance of the phos-
of phospholes 3 as chiral intermediates for the synthesis phorus substituent. When R* ϭ myrtanyl, the steric hind-
of new phosphorus derivatives through either DielsϪAlder rance around the phosphorus atom was greatly reduced and
cycloaddition reactions on the dienic system or [1,5] the DielsϪAlder reaction with DMAD leads to the ex-
sigmatropic shifts of the aryl moiety of 3c. Results are pected 7-phosphanorbornadiene 5b, which was isolated and
given hereafter.
fully characterized.
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Eur. J. Inorg. Chem. 2002, 1657Ϫ1665

Optically Active Phospholes
FULL PAPER
The generation and trapping of the pentacarbonyl(P- ambiguous assignment was prevented by the presence of the
myrtanylphosphinidene)tungsten complex from 5b was two inseparable isomers 9a and 9b, in a 4:1 ratio.
checked in small-scale experiments by 31P NMR spectro-
scopy on crude reaction mixtures (Scheme 4). Diphenylac-
etylene, phenylacetylene, and trans-stilbene were used as
trapping reagents because, in such cases, the anticipated
complexed phosphirene and phosphirane products should
give very characteristic 31P NMR signals at high-field
shifts.[14,17]
These experiments show that thermolysis of 5b under the
usual experimental conditions,[14,17] affords the pentacar-
bonyl(P-myrtanylphosphinidene)tungsten complex 6b,
which displays the expected electrophilic behavior toward
olefins and alkynes. Phosphirane and phosphirene com-
plexes are obtained as the only reaction products, by [2ϩ1]
cycloaddition reactions.
Scheme 5. Reaction of the {3,4-dimethyl-1-[2-(4-isopropyl-4,5-dihy-
In the case of unsymmetrical alkynes and olefins, chiral
induction from the optically active myrtanyl substituent
should give diastereoselective addition reactions. Unfortu-
nately, mixtures of diastereomers, with rather poor diastere-
omeric excesses, are obtained upon cycloaddition of 6b with
phenylacetylene and trans-stilbene, leading to 7b and 8, re-
spectively. To be stereoselective, the reaction with phenyl-
acetylene requires diastereoselective formation of a chiral
phosphorus center, while the diastereoselective addition of
6b on trans-stilbene requires enantiofacial selectivity. The
low efficiency of the myrtanyl group as chiral auxiliary in
both these reactions is probably due to the presence of the
flexible CH2 spacer between the phosphorus atom and the
chiral centers of the myrtanyl moiety. The diastereoselectiv-
ity is likely to be improved by using chiral auxiliaries bear-
ing stereogenic centers closer to the phosphorus atom.[18]
Finally, trapping reactions of the P-myrtanylphosphinid-
ene 6b should give a convenient access to optically pure
phosphirane[19] and phosphirene derivatives, but only when
symmetrically substituted unsaturated substrates are used,
as shown by the synthesis of 7a. Otherwise, separation of
the diastereomeric mixtures would be required.
dro-1,3-oxazol-2-yl)phenyl]phosphole}W(CO)5 complex 4c with di-
methyl acetylenedicarboxylate
To confirm the structural assignment, we decided to per-
form the same reaction starting from the achiral (oxazolyl-
phenyl)phosphole complex 4d, which should lead to a single
isomer of the final product and thus facilitate its purifica-
tion and characterization (Scheme 6).
Scheme 6. Reaction of the {3,4-dimethyl-1-[2-(4,4-dimethyl-4,5-di-
hydro-1,3-oxazol-2-yl)phenyl]phosphole}W(CO)5 complex 4d with
dimethyl acetylenedicarboxylate
The expected reaction between the phosphole complex 4d
and DMAD led to the 7-aza-1-phosphanorbornadiene 9d,
which was easily isolated and fully characterized. An X-ray
diffraction study of 9d confirmed the proposed structure
(Figure 1).
Given that several procedures are known for removing
phosphirenes and phosphiranes from their pentacarbonyl-
tungsten or -molybdenum complexes,[20Ϫ22] reactions in
Scheme 4 should represent new potential sources of chiral
ligands for enantioselective catalysis.
In the reaction of the phosphole complex 4c {R* ϭ 2-
[(S)-4-isopropyloxazolino]phenyl} with DMAD, the ex-
pected 7-phosphanorbornadiene derivative 5c was not de-
tected. Nevertheless, a clean reaction occurred to give a new
phosphorus derivative as a mixture of two isomers. Spectro-
scopic data and NMR analysis of the crude reaction mix-
ture showed formation of dimethyl phthalate. This suggests
that the DielsϪAlder reaction took place as expected, but
that the 7-phosphanorbornadiene complex decomposed in-
stantaneously to generate the corresponding phosphinidene
6c (Scheme 3). The excess DMAD was suspected to be the
trapping reagent for the intermediate phosphinidene.
This hypothesis is supported by spectroscopic analysis of
the pure final product, which was in agreement with the
Figure 1. ORTEP diagram for complex 9d; selected bond lengths
˚
[A]: WϪP 2.4495(7), PϪN 1.707(2), PϪC(8) 1.845(3), PϪC(3)
1.890(3), NϪC(1) 1.474(3); selected bond angles [°]: PϪWϪC(18)
172.13(9),
C(3)ϪPϪC(8)
94.4(1),
PϪNϪC(1)
100.0(2),
bicyclic structure 9 shown in Scheme 5. Nevertheless, an un- C(1)ϪNϪC(5) 106.9(2), O(1)ϪC(1)ϪN 106.1(2)
Eur. J. Inorg. Chem. 2002, 1657Ϫ1665
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X. Sava, A. Marinetti, L. Ricard, F. Mathey
FULL PAPER
To date, only one example of a 7-aza-1-phosphanorbor- other than DMAD can be used as trapping reagents
nadiene has been reported,[23] which was obtained by trap- (Scheme 8). In the presence of methyl acrylate (or ethyl
ping a (pentamethylcyclopentadienyl)phosphinidene com- phenylpropionate), diastereomeric mixtures of the bicyclic
plex with a nitrile. The first formed adduct rearranges derivatives 10a (or 10b) were obtained. However, complex
through a [4ϩ2] cycloaddition to give the norbornadiene.
9 is still formed in some amount (10/9 ഠ 80:20), even when
In the reactions of Schemes 5 and 6, formation of the 7- a threefold excess of the trapping reagent was used, showing
aza-1-phosphanorbornadiene complexes 9 can be explained that DMAD competes well with the other reagents. The
as follows. The [4ϩ2] cycloaddition between 4c (or 4d) and whole reaction sequence can be improved by using ethyl
excess DMAD gives the 7-phosphanorbornadiene complex phenylpropionate as the only cycloaddition partner for both
5c (or 5d), which instantaneously generates the correspond- the DielsϪAlder reaction on phosphole 4d and the phos-
ing phosphinidene complex. The easy decomposition of phinidene trapping. Under such conditions, the crude reac-
these 7-phosphanorbornadiene complexes can be explained tion mixture contains complex 10 as the major product.
by the intramolecular interaction between the phosphorus
atom and the nitrogen lone pair of the oxazoline moiety, as
it has already been shown that amines and strongly basic
phosphanes catalyze such reactions.[24] The phosphinidene
complex is thus generated as an adduct between the imine
nitrogen atom and the electron-deficient phosphorus atom,
which can be described by the two resonance structures I
and II in Scheme 7.
Scheme 8. Reactivity of the {3,4-dimethyl-1-[2-(4,4-dimethyl-4,5-
dihydro-1,3-oxazol-2-yl)phenyl]phosphole}W(CO)5 complex 4d
To summarize, the cycloaddition reactions shown in
Scheme 7. {P-[2-(4-Isopropyl-4,5-dihydro-1,3-oxazol-2-yl)phenyl]-
Schemes 6 and 8 demonstrate the generation of new phos-
phinidene intermediates, which display an unprecedented
1,3-dipolar behavior. Their reactivity allows the synthesis of
new tricyclic 7-aza-1-phosphanorbornadiene derivatives.
Application of such reactions to the preparation of new
optically pure ligands for transition metal catalysis should
be possible, provided that the separation of the diastereoiso-
mers of 9 (or 10) and the removal of the azaphosphanor-
bornadienes from their tungsten complexes could be per-
formed. Although 7-aza-1-phosphanorbornadienes are new
compounds whose catalytic properties are difficult to pre-
dict, the use of 1-phosphanorbornadienes as auxiliaries in
transition metal catalysis, including asymmetric catalysis, is
already well documented.[31]
phosphinidene}W(CO)5 complex 6c
Structure II clearly emphasizes the 1,3-dipolar nature of
the adduct and explains its [3ϩ2] cycloaddition with
DMAD leading to 9. The reaction intermediate of
Scheme 7, can be considered as a phosphaazomethine ylide.
As far as we know, phosphinideneϪimine adducts have
never been described before. However, other P/N adducts
are known. A pyrazolylϪphosphinidene complex has been
reported by Cowley. In this case, the coordination of the
nitrogen lone pair substantially reduced the electrophilicity
of the phosphinidene, thus permitting its isolation.[25]
PhosphinideneϪnitrile adducts have been generated as re-
active intermediates and their reactivity in 1,3-dipolar
cycloadditions has been studied by Streubel.[26Ϫ28]
Studies on the synthetic applications of the 1,3-dipolar
cycloadditions above are in progress.
Azomethine ylides,[29] as well as (iminomethylene)phos-
phoranes and analogs[30] were found to be useful as syn-
thetic building blocks through [3ϩ2] cycloadditions. Thus,
the use of the phosphaazomethine ylides above as synthetic
tools can be envisaged.
Synthesis of Chiral Phosphaferrocene Derivatives
Results given in Schemes 5 and 6 point out the strongly
Phosphaferrocenes[32] are usually obtained from phos-
nucleophilic behavior of the (2-oxazolylphenyl)phosphinid- pholes by two different procedures: 1) lithium-induced
ene complexes, which contrasts with that of simple alkyl- or cleavage of the phosphorus substituent and reaction of the
aryl-substituted
pentacarbonyl(phosphinidene)tungsten phospholyl anion with either iron halides[33,34] or arene(cy-
complexes. Further experiments showed that the [3ϩ2] clopentadienyl)iron derivatives;[35] and 2) thermal [1,5]
cycloaddition with DMAD took place preferentially even in sigmatropic shift of the phosphorus substituent and sub-
the presence of excess diphenylacetylene, an usually efficient sequent trapping of the intermediate 2H-phosphole by suit-
phosphinidene trapping reagent.
able iron complexes.[36,37] The second approach was selected
Preliminary tests (31P NMR analysis of crude reaction for the synthesis of phosphaferrocenes starting from phos-
mixtures) show that electron-deficient olefins and alkynes phole 4c and [CpFe(CO)2]2 (Scheme 9).
1660
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Optically Active Phospholes
FULL PAPER
substituted phosphaferrocenes display planar chirality, so
the formation of two diastereoisomers was expected. Chiral
induction from the oxazoline moiety favors one of them,
but the diastereoselectivity level is not yet satisfactory.
Purification of the final products 11 and separation of
isomers, proved to be difficult because of their air sensitiv-
ity. Thus, complexation of the phosphaferrocenes by penta-
carbonyltungsten or -molybdenum was envisaged and fur-
nished stable, easily isolable species (Scheme 10).
The main product obtained by reaction of 11 with an
excess of the tungsten complex (THF)W(CO)5, was the di-
metallic complex 12, where both the phosphorus and nitro-
gen atoms are complexed by a W(CO)5 group. The major
Scheme 9. Synthesis of the phosphaferrocene derivatives 11
Under the usual reaction conditions, the aryl group of 4c
underwent a [1,5] sigmatropic shift, followed by depro-
tonation of the 2H-phosphole and complexation to the
cyclopentadienyliron moiety to afford 11 as a mixture of
two isomers in a 1:2 ratio and in a moderate yield. The α-
Scheme 10. Tungsten and molybdenum complexes of the phos-
phaferrocene 11
Figure 3. ORTEP diagrams for the molybdenum and tungsten com-
˚
plexes 14a and 13b; selected bond lengths [A]: 14a: MoϪP 2.475(1),
MoϪN 2.277(4), FeϪP 2.240(2); 13b: WϪP 2.425(3), WϪN
2.274(8), FeϪP 2.231(3); selected bond angles [°]: 14a: PϪMoϪN
79.4(1), C(1)ϪPϪC(4) 90.6(3), C(11)ϪNϪC(13) 106.9(4),
Figure 2. ORTEP diagram for the tungsten complex 12a; selected
˚
bond lengths [A]: W(1)ϪP 2.462(2), W(2)ϪN 2.284(5), FeϪP
2.253(2); selected bond angles [°]: C(1)ϪPϪC(4) 91.8(3), MoϪNϪC(11) 130.1(4), MoϪNϪC(13) 122.6(3); 13b: PϪWϪN
C(11)ϪNϪC(13)
107.7(5),
W(2)ϪNϪC(11)
130.0(4), 79.5(2), C(1)ϪPϪC(4) 91.9(5), C(11)ϪNϪC(13) 107.7(8),
WϪNϪC(11) 128.4(7), WϪNϪC(13) 123.8(6)
W(2)ϪNϪC(13) 122.2(4)
Eur. J. Inorg. Chem. 2002, 1657Ϫ1665
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X. Sava, A. Marinetti, L. Ricard, F. Mathey
FULL PAPER
diastereomer, (S,S)-12a (M ϭ W), was obtained in pure
form after crystallization. Its structure was confirmed by
X-ray crystallography, as shown in Figure 2.
Minor amounts of the chelate derivative 13 (M ϭ W)
were also present in the reaction mixture. Crystals of one
diastereomer (13b) were isolated and analyzed by X-ray
crystallography (Figure 3, bottom). Its absolute configura-
tion was determined as (S,S).
In the reaction with the molybdenum complex
(THF)Mo(CO)5, the P,N-bidentate phosphaferrocene 11
exclusively formed the chelate derivative 14 (M ϭ Mo) as
an isomeric mixture. The main isomer was obtained in pure
form after crystallization and was characterized by X-ray
diffraction studies. The ORTEP drawing for 14a as well as
selected bond angles and distances are given in Figure 3
(top). From the X-ray data, an (R,S) absolute configuration
can be assigned to the isolated complex.
Experimental Section
General: All reactions were routinely performed under nitrogen by
using Schlenk technique and dry deoxygenated solvents. NMR
spectra were obtained at 25 °C with a Bruker AC 200 SY spectro-
meter operating at 200.13 MHz for H, 50.32 MHz for 13C, and
1
81.01 MHz 31P. Chemical shifts are expressed in ppm downfield
from external TMS (1H and 13C) and 85% H3PO4 (31P), and coup-
ling constants are given in Hz. Mass spectra were obtained at 70 eV
with an HP 5989 B spectrometer coupled with an HP 5890 chroma-
tograph by the direct inlet method. IR spectra were obtained with
a PerkinϪElmer 297. Elemental analyses were performed by the
Service d’Analyse du CNRS at Gif sur Yvette, France.
1-(2-Isopropyl-5-methylcyclohexyl)-3,4-dimethylphosphole (3a):
A
solution of lithium 3,4-dimethylphospholide in 30 mL of THF was
prepared by treating 3,4-dimethyl-1-phenylphosphole (3 g,
16 mmol) with excess lithium at room temperature. Menthyl mesyl-
ate (3.7 g, 16 mmol) was added, and the solution was allowed to
reflux for 1 h. After hydrolysis, evaporation of THF, and extraction
of the aqueous layer with diethyl ether, the organic phase was dried
with MgSO4. The product was purified by chromatography on sil-
ica gel with hexanes, affording 3a as a colorless oil. Yield: 25%
(1.0 g). 31P NMR (CDCl3): δ ϭ Ϫ3.0. 1H NMR (CDCl3): δ ϭ 0.85
Isolation of complexes 13 and 14 shows that the geo-
metry of the P,N-bidentate ligand 11 is suitable for chelate
formation. This is a key feature of the ligand, as far as its
use as a chiral auxiliary in catalysis is concerned. The high
catalytic efficiency of oxazolines coupled with phosphanyl-
ferrocene moieties is well established to date,[38] and the use (d, 3JH,H ϭ 6.1 Hz, 3 H, Me), 0.94 (d, 3J ϭ 6.4 Hz, 3 H, Me), 0.95
of phosphaferrocenes in catalysis is a field of growing inter-
(d, 3J ϭ 6.5 Hz, 3 H, Me), 1.04Ϫ1.99 (m, 9 H), 2.08 [s, 3 H,
C(CH3)], 2.09 [s, 3 H, C(CH3)], 2.56 (m, 1 H), 6.41 (d, JP,H
2
est.[39] Thus, ligands 11, which associates the phosphaferro-
cene and the oxazoline moieties, should find interesting ap-
plications in organometallic asymmetric catalysis. Neverthe-
less, improvement of the synthetic approach and an efficient
separation procedure for the two diastereomers 11a and 11b
is required.
ϭ
36.9 Hz, 2 H, 2-H and 5-H). 13C NMR (CDCl3): δ ϭ 17.75 (Me),
17.81 (Me), 21.2 (Me), 21.5 (Me), 22.7 (Me), 26.5 (d, J ϭ 8.7 Hz,
CH2), 28.7 (d, J ϭ 6.1 Hz, CH), 31.2 (d, J ϭ 7.8 Hz, CH), 36.1
(CH2), 38.8 (d, J ϭ 4.6 Hz, CH), 42.6 (CH2), 48.8 (d, J ϭ 11.6 Hz,
CH), 129.1 (CHϭ), 146.5 (CHϭ), 146.7 (s, C).
(S)-2-[2-(3,4-Dimethyl-1H-phosphol-1-yl)phenyl]-4-isopropyl-4,5-
dihydro-1,3-oxazole (3c): A mixture of lithium 3,4-dimethylphos-
pholide (96 mmol), prepared from lithium metal and 3,4-dimethyl-
1-phenylphosphole (18.0 g, 96 mmol), and (S)-2-(2-fluorophenyl)-
4-isopropyl-4,5-dihydrooxazole (14.8 g, 72 mmol) in THF was
heated at 45 °C for 48 h. After hydrolysis and extraction of the
aqueous layer with diethyl ether, the organic phase was dried with
MgSO4. After evaporation of the solvent, the residue was purified
by chromatography on silica gel with a hexane/ether (95:5) mixture,
giving 3c as a colorless oil. Yield: 61% (13.0 g). 31P NMR (CDCl3):
δ ϭ 0.9. 1H NMR (CDCl3): δ ϭ 0.99 [d, J ϭ 6.7 Hz, 3 H,
CH(CH3)2], 1.10 [d, J ϭ 6.7 Hz, 3 H, CH(CH3)2], 1.87 [m, J ϭ
An alternative synthetic approach to the phosphaferro-
cenes 11 and other metallocene analogs could be the forma-
tion of the corresponding phospholylpotassium derivative
after [1,5] shift of the aryl group.[40] The phospholyl anion
could be treated with various metal halide complexes under
milder conditions, and would hopefully be more diastereo-
selective in its outcome.
Conclusion
4
6.6 Hz, 1 H, CH(CH3)2], 2.10 (d, JP,H ϭ 4.2 Hz, 6 H, CH3), 4.29
(m, 3 H, CHN and OCH2), 6.62 (d, 2J P,H ϭ 34.3 Hz, 2 H, PϪCH),
7.24Ϫ7.31 (m, 2 H, Ar-H), 7.35Ϫ7.41 (m, 1 H, Ar-H), 7.79Ϫ7.86
This work shows that phospholes bearing various optic-
ally pure substituents at the phosphorus atom are easily ac-
cessible species. They can either be applied as chiral auxili-
aries in asymmetric transition metal catalysis or used as ver-
satile synthons. As a very preliminary study, we have shown
here that chiral phosphinidene complexes and phosphafer-
rocene derivatives can be obtained from these phospholes.
The (oxazolylphenyl)phosphole 3c seems to be a particu-
larly promising starting material. On one hand, an unpre-
cedented, [1,3]-dipole-like reactivity of the corresponding
terminal phosphinidene complex has been demonstrated,
and on the other hand, phosphole 3c underwent a [1,5]-
sigmatropic shift of the phosphorus substituent and should
allow application of the well-known 2H-phosphole chem-
3
(m, 1 H, Ar-H). 13C NMR (CDCl3): δ ϭ 17.8 (d, J ϭ 2.3 Hz, 2
CH3), 18.7 [CH(CH3)2], 19.1 [CH(CH3)2], 33.1 [CH(CH3)2], 70.4
(OCH2), 73.5 (CHN), 127.6 (CH), 128.9 (d, J ϭ 13.8 Hz, CH),
2
129.1 (CH), 130.4 (CH), 130.7 (d, J ϭ 18.6 Hz, C), 133.5 (CH),
136.4 (d, 1J ϭ 21.4 Hz, C), 147.7 (d, 2J ϭ 9.5 Hz, C), 147.9 (d,
2J ϭ 10.5 Hz,), 162.8 (CϭN). MS: m/z (%) ϭ 299 (78) [Mϩ], 230
(100). C18H22NOP (299.35): calcd. C 72.22, H 7.41, N 4.68; found
C 71.88, H 7.54, N 4.51. [α]D ϭ ϩ64 (c ϭ 1, toluene).
2-[2-(3,4-Dimethyl-1H-phosphol-1-yl)phenyl]-4,4-dimethyl-4,5-
dihydro-1,3-oxazole (3d): A mixture of lithium 3,4-dimethylphos-
pholide (48 mmol), prepared from lithium metal and 3,4-dimethyl-
1-phenylphosphole (9.0 g, 48 mmol), and 2-(2-fluorophenyl)-4,4-di-
methyl-4,5-dihydrooxazole (8.9 g, 46 mmol) in 40 mL of THF was
heated at 45 °C for 48 h. After hydrolysis, evaporation of THF, and
istry to the asymmetric synthesis of phosphorus derivatives. extraction of the aqueous layer with diethyl ether, the solution was
1662 Eur. J. Inorg. Chem. 2002, 1657Ϫ1665

Optically Active Phospholes
FULL PAPER
dried with MgSO4. After concentration, the residue was purified
by chromatography on a silica gel column with hexane/ether (95:5)
24:1 to 9:1) affording 4c as a yellow powder (Rf ϭ 0.4 in hexane/
diethyl ether, 3:2),. Yield: 85% (1.34 g). 31P NMR (CDCl3): δ ϭ 9.2
1
1
as the eluent. Yield: 70% (9.2 g). 31P NMR (CDCl3): δ ϭ 0.2. H
(1JP,W ϭ 213 Hz). H NMR (CDCl3): δ ϭ 1.00 [d, J ϭ 6.7 Hz, 3
4
NMR (CDCl3): δ ϭ 1.43 [s, 6 H, C(CH3)2], 2.09 (dd, JP,H ϭ 4.0, H, CH(CH3)2], 1.09 [d, J ϭ 6.7 Hz, 3 H, CH(CH3)2], 2.08 [m, J ϭ
4J ϭ 0.5 Hz, 6 H, CH3), 4.13 (s, 2 H, OCH2), 6.59 (dd, J
ϭ
5.3 Hz, 1 H, CH(CH3)2], 2.12 (s, 3 H, CH3), 2.18 (s, 3 H, CH3),
4.22Ϫ4.53 (m, 3 H, CHN and OCH2), 6.64 (d, JP,H ϭ 33.0 Hz, 1
P,H
4
34.6, J ϭ 0.5 Hz, 2 H, PϪCH), 7.2Ϫ7.3 (m, 3 H, Ar-H), 7.7Ϫ7.8
(m, 1 H, Ar-H). 13C NMR (CDCl3): δ ϭ 17.7 (d, 3J ϭ 2.8 Hz, H, PϪCH), 6.90 (d, JP,H ϭ 32.9 Hz, 1 H, PϪCH), 7.39Ϫ7.45 (m,
CH3), 28.5 [C(CH3)2], 68.4 [C(CH3)2], 79.0 (OCH2), 127.7 (CH-
2 H, Ar-H), 7.57Ϫ7.67 (m, 1 H, Ar-H), 8.0Ϫ8.1 (m, 1 H, Ar-H).
Ar), 128.9 (PϪCH), 129.1 (d, 2J ϭ 4.3 Hz, C), 130.3 (CH-Ar), 13C NMR (CDCl3): δ ϭ 17.1 (d, 3J ϭ 10.1, Me), 17.3 (d, 3J ϭ
1
131.2 (d, 2J ϭ 19.6 Hz, C), 133.4 (CH-Ar), 135.1 (d, J ϭ 21.4 Hz, 11.1 Hz, Me), 17.6 [CH(CH3)2], 19.0 [CH(CH3)2], 32.3 [CH(CH3)2],
2
C), 147.9 (d, J ϭ 10.6 Hz), 161.8 (s, CϭN).
69.6 (OCH2), 72.7 (CHN), 129.1 (d, J ϭ 10.5 Hz), 129.6, 129.7,
130.0 (d, J ϭ 6.0 Hz), 130.6, 130.7, 131.8 (d, J ϭ 7.0 Hz), 134.0 (d,
1J ϭ 35.1 Hz, PCH), 148.9 (d, 2J ϭ 9.8 Hz, C), 149.1 (d, 2J ϭ
10.2 Hz, C), 162.1 (CϭN), 196.9 (d, 2J ϭ 7.1 Hz, 4 COcis), 200.0
{1-(2-Isopropyl-5-methylcyclohexyl)-3,4-dimethylphosphole}W-
(CO)5 (4a): A solution of hexacarbonyltungsten (1.55 g, 4.4 mmol)
in 250 mL of THF was irradiated under UV light for 30 min. To
this solution was added a solution of 3a (1.0 g, 4 mmol) in 10 mL
of THF. After 1 h of stirring, the solvent was evaporated. The prod-
uct was then purified by chromatography on silica gel, with hexane
as eluent (Rf ϭ 0.25), affording 4a as a yellow powder. Yield: 91%
2
(d, J ϭ 18.5 Hz, COtrans). MS: m/z (%) ϭ 623 (1) [Mϩ], 595 (33)
[M Ϫ CO], 380 (100).
{2-[2-(3,4-Dimethyl-1H-phospholyl)phenyl]-4,4-dimethyl-4,5-
dihydro-1,3-oxazole}W(CO)5 (4d): A solution of hexacarbonyl-
(2.1 g). 31P NMR (CDCl3): δ ϭ 11.4 (1JP,W ϭ 203.2 Hz). 1H NMR tungsten (1.85 g, 5.2 mmol) in 250 mL of THF was irradiated un-
(CDCl3): δ ϭ 0.80 (d, 3J ϭ 6.0 Hz, 3 H, Me), 0.92 (d, 3J ϭ 6.0,
Hz, 3 H, Me), 0.93 (d, 3J ϭ 6.1 Hz, 3 H, Me), 1.14Ϫ1.80 (m, 8 H), 3d (1.5 g, 5.2 mmol) in 10 mL of THF. After 30 min of stirring, the
2.15 (s, 6 H, CH3), 2.32Ϫ2.45 (m, 1 H), 2.77 (s, 1 H), 6.43 (d, solvent was evaporated. The product was then purified by chroma-
der UV light for 30 min. To this solution was added a solution of
2
2JP,H ϭ 37.2 Hz, 1 H, PCH), 6.53 (d, JP,H ϭ 36.7 Hz, 1 H, PCH). tography on silica gel, with a hexane/diethyl ether gradient. Com-
3
3
13C NMR (CDCl3): δ ϭ 17.8 (d, J ϭ 3.4 Hz, Me), 17.1 (d, J ϭ plex 4c was obtained as a yellow powder (Rf ϭ 0.35 in hexane/
4.4 Hz, Me), 21.6 (Me), 21.8 (Me), 22.24 (Me), 26.0 (d, J ϭ 2.8 Hz, diethyl ether, 3:2). Yield: 80% (2.54 g). 31P NMR (CDCl3): δ ϭ 11.8
1
CH2), 28.8 (CH), 30.13 (CH), 35.4 (CH2), 39.8 (d, J ϭ 5.9 Hz,
(1JP,W ϭ 214 Hz). H NMR (CDCl3): δ ϭ 1.50 [s, 6 H, C(CH3)2],
CH2), 42.1 (d, J ϭ 14.6 Hz, CH), 50.9 (d, J ϭ 6.0 Hz, CH), 131.3 2.12 (s, 6 H, CH3), 4.19 (s, 2 H, OCH2), 6.72 (dd, JP,H ϭ 33.2, 4J ϭ
1
1
(d, J ϭ 38.1 Hz, PCH), 131.8 (d, J ϭ 35.2 Hz, PCH), 146.3 (d,
0.8 Hz, 2 H, PϪCH), 7.37Ϫ7.47 (m, 2 H, Ar-H), 7.53Ϫ7.63 (m, 1
2J ϭ 9.3 Hz, C), 146.5 (d, J ϭ 9.0 Hz, C), 197.0 (d, J ϭ 6.2 Hz, H, Ar-H), 7.98Ϫ8.04 (m, 1 H, Ar-H). 13C NMR (CDCl3): δ ϭ
2
2
2
3
4 COcis), 199.3 (d, J ϭ 16.8 Hz, COtrans). MS (EI): m/z (%) ϭ 574
17.3 (d, J ϭ 11.8 Hz, CH3), 28.3 [C(CH3)2], 68.8 [C(CH3)2], 79.2
(7) [Mϩ], 192 (100).
(OCH2),129.3 (d, J ϭ 5.1 Hz, C), 128.8, 129.4, 129.7, 130.5, 130.7,
1
2
130.8, 131.9, 132.0, 134.1 (d, J ϭ 35.1 Hz, PCH), 149.1 (d, J ϭ
{1-[(6,6-Dimethylbicyclo[3.1.1]hept-2-yl)methyl]-3,4-dimethyl-1H-
phosphole}W(CO)5 (4b): A mixture of lithium 3,4-dimethylphos-
pholide (56 mmol), prepared from lithium metal and 3,4-dimethyl-
2
10.7 Hz, C), 160.9 (CϭN), 197.2 (d, J ϭ 7.2 Hz, COcis), 200.4 (d,
2J ϭ 19.6 Hz, COtrans).
1-phenylphosphole (10.5 g, 56 mmol) in 60 mL of THF, and hexa- {Dimethyl 7-[(6,6-dimethylbicyclo[3.1.1]hept-2-yl)methyl]-5,6-di-
carbonyltungsten (19.7 g, 56 mmol) was stirred for 24 h at room methyl-7-phosphabicyclo[2.2.1]hepta-2,5-diene-2,3-dicarboxylate}
temperature. Then 13.0 g (56 mmol) of myrtanyl mesylate were ad- W(CO)5 (5b): To a solution of 4b (11.4 g, 20 mmol) in 50 mL of
ded and the mixture was stirred again for 48 h. After hydrolysis,
the THF was evaporated under vacuum. The residue was extracted
with diethyl ether, and the organic layer dried with MgSO4. The
product was then purified by chromatography on silica gel with
hexane as eluent. Yield: 42% (13.5 g). 31P NMR (CDCl3): δ ϭ 5.8
toluene was added 15 mL (120 mmol) of dimethyl acetylenedicar-
boxylate. The solution was heated to 84 °C for 30 h. The solvent
was evaporated under vacuum. The residue was purified by chro-
matography on silica gel with hexane/diethyl ether (95:5) as the
eluent. Recrystallization afforded pure 5b as yellow crystals. Yield:
(JP,W ϭ 206.9 Hz). 1H NMR (CDCl3): δ ϭ 0.85 (d, J ϭ 12.3 Hz, 1 74% (10.5 g). 31P NMR (CDCl3): δ ϭ 217.5 (1JP,W ϭ 234.3 Hz).
H), 0.94 [s, 3 H, C(CH3)2], 1.19 [s, 3 H, C(CH3)2], 1.2Ϫ1.4 (m, 1
1H NMR (CDCl3): δ ϭ 0.90 (d, J ϭ 9.9 Hz, 1 H) 0.97 [s, 3 H,
H), 1.8Ϫ2.1 (m, 8 H), 2.16 (s, 6 H, CH3), 2.2Ϫ2.3 (m, 1 H), 6.28 C(CH3)2], 1.16 [s, 3 H, C(CH3)2], 1.40 (m, 1 H), 1.72Ϫ1.80 (m, 1
2
2
(d, JP,H ϭ 36.7 Hz, 1 H, P-CH), 6.33 (d, JP,H ϭ 36.7 Hz, 1 H, H), 1.83Ϫ1.90 (m, 3 H), 1.94 (s, 3 H, CH3), 1.95 (s, 3 H, CH3),
PϪCH). 13C NMR (CDCl3): δ ϭ 17.1 (Me), 17.3 (Me), 23.3 (CH3), 2.19Ϫ2.58 (m, 5 H), 3.56 (m, 2J ϭ 3.0, 4J ϭ 3.0 Hz, 2 H,
P,H
23.9 (d, 3J ϭ 4.7 Hz, CH2), 26.1 (CH2), 27.8 (CH3), 32.9 (CH2), PϪCH), 3.82 (s, 3 H, OCH3), 3.84 (s, 3 H, OCH3). 13C NMR
38.4 (PϪCH2ϪCH), 38.5 [C(CH3)2], 38.7 (d, 1J ϭ 22.9 Hz, (CDCl3): δ ϭ 15.9 (Me), 16.0 (Me), 22.6 (d, 3J ϭ 4.5 Hz, CH2),
PϪCH2), 40.8 (CH), 48.1 (d, 3J ϭ 10.3 Hz, CH), 129.3 (d, 1J ϭ 22.6 (CH3), 26.2 (CH2), 27.9 (CH3), 33.8 (CH2), 38.3 (d, 1J ϭ
1
2
17.0 Hz, PϪCH), 130.1 (d, J ϭ 18.1 Hz, PϪCH), 149.8 (d, J ϭ 17.9 Hz, PϪCH2), 38.5 [C(CH3)2], 41.0 (CH), 43.1 (PϪCH2CH),
7.8 Hz, C), 150.2 (d, 2J ϭ 7.8 Hz, C), 196.4 (d, 2J ϭ 7.2 Hz, 4
47.3 (d, J ϭ 7.7 Hz, CH), 52.5 (OMe), 59.9 (d, J ϭ 19.6 Hz, P-
3
1
COcis), 199.3 (d, J ϭ 16.7 Hz, COtrans). MS: m/z (%) ϭ 572 (26) CH), 60.3 (d, 1J ϭ 18.4 Hz, P-CH), 138.9 (d, 2J ϭ 2.6 Hz, C), 139.1
2
[Mϩ], 407 (100). C21H25O5PW (572.23): calcd. C 44.08, H 4.40;
found C 43.69, H 4.41.
(d, J ϭ 14.6 Hz, C), 145.3 [d, J ϭ 5.1 Hz, C(CO2Me)], 146.0 [d,
2J ϭ 4.8 Hz, C(CO2Me)], 165.0 [d, 3J ϭ 3.0 Hz, C(CO2Me)], 165.4
[d, 3J ϭ 2.7 Hz, C(CO2Me)], 196.2 (d, 2J ϭ 6.6 Hz, 4 COcis), 197.8
2
2
{(S)-2-[2-(3,4-Dimethyl-1H-phosphol-1-yl)phenyl]-4-isopropyl-4,5-
dihydro-1,3-oxazole}W(CO)5 (4c): A solution of hexacarbonyl-
tungsten (0.89 g, 2.5 mmol) in 250 mL of THF was irradiated un-
der UV for 30 min. To this solution was added a solution of 3c
2
(d, J ϭ 25.7 Hz, COtrans). MS: m/z (%) ϭ 714 (4) [Mϩ], 191 (100).
(7-Aza-1-phosphabicyclo[2.2.1]hept-2-ene)W(CO)5 Complexes 9a
and 9b: A solution of 4c (0.66 g; 1.0 mmol) and dimethyl acetylene-
(0.76 g, 2.5 mmol) in 10 mL of THF. After 30 min of stirring, the dicarboxylate (0.26 mL; 2.1 mmol) in 3 mL of toluene was heated
solvent was evaporated. The product was then purified by chroma- under reflux for 15 h. The crude mixture was purified directly by
tography on silica gel with a hexane/diethyl ether gradient (from chromatography on silica gel with toluene as eluent. Two diastereo-
Eur. J. Inorg. Chem. 2002, 1657Ϫ1665
1663

X. Sava, A. Marinetti, L. Ricard, F. Mathey
FULL PAPER
mers were obtained in a 4:1 ratio. Yield: 63% (0.43 g). 31P NMR
(toluene): δ ϭ 38.5 (minor diastereomer), 41.8 (major diastere-
(CDCl3): δ ϭ 0.42 [d, J ϭ 6.7 Hz, 3 H, CH(CH3)2], 0.88 [d, J ϭ
7.0 Hz, 3 H, CH(CH3)2], 2.11 (s, 3 H, CH3), 2.20 (s, 3 H, CH3),
omer). The mixture was dissolved in toluene and layered with hex- 2.63 [m, 1 H, CH(CH3)2], 3.70 (d, J
ϭ 32.4 Hz, PϪCH),
P,H
ane. Storage of the solution at 6 °C gave orange crystals of the
3.93Ϫ4.34 (m, 3 H, CHN, OCH2), 4.51 (s, 5 H, Cp), 7.49Ϫ7.61 (m,
main diastereomer. 31P NMR (CDCl3): δ ϭ 42.1 (1JP,W ϭ 289 Hz).
4 H, Ar-H). 13C NMR (CDCl3): δ ϭ 12.9 [CH(CH3)2], 15.4 (d,
1H NMR (CDCl3): δ ϭ 0.68 [d, J ϭ 7.0 Hz, 3 H, CH(CH3)2], 0.71 J ϭ 3.0 Hz, Me), 16.2 (d, J ϭ 4.5 Hz, Me), 19.0 [CH(CH3)2], 29.9
[d, J ϭ 6.6 Hz, 3 H, CH(CH3)2], 2.00 [m, J ϭ 3.5 Hz, 1 H, [CH(CH3)2], 67.8 (OCH2), 69.9 (PϪCH), 74.1 (Cp), 77.5 (CHN),
CH(CH3)2], 3.33 (m, J ϭ 14.9 et 3.5 Hz, 1 H, CHN), 3.54 (s, 3 H, 93.1 (C), 93.12 (C), 93.7 (d, J ϭ 2.2 Hz, PϪC), 127.7 (CH-Ar),
OMe), 3.59 (s, 3 H, OMe), 4.00 (AB, J ϭ 7.7 Hz, 2 H, OCH2),
6.91Ϫ7.14 (m, 2 H, Ar-H), 7.33Ϫ7.38 (m, 1 H, Ar-H), 7.41Ϫ7.53
130.1 (CH-Ar), 130.9 (d, J ϭ 3.2 Hz, C), 131.3 (CH-Ar), 133.9 (d,
J ϭ 3.5 Hz, CH-Ar), 134.4 (d, J ϭ 13.8 Hz, C-2Ј), 171.6 (CϭN),
(m, 1 H, Ar-H). 13C NMR (CDCl3): δ ϭ 14.5 (Me), 19.8 (Me), 194.5 (d, J ϭ 8.0 Hz, COcis-P), 197.8 (COcis-N), 197.8 (d, J ϭ
29.0 [CH(CH3)2], 52.6 (OMe), 52.7 (OMe), 58.6 (d, 2J ϭ 2.6 Hz, 32.0 Hz, COtrans-P), 200.8 (COtrans-N). C33H26FeNO11PW2 (1067.06):
3
NϪCH), 72.9 (d, J ϭ 7.6 Hz, OCH2), 115.8 (NϪCϪO), 121.3 (d, calcd. C 37.14, H 2.46; found C 37.22, H 2.33. [α]D ϭ Ϫ249 (c ϭ
J ϭ 3.0 Hz, CH-Ar), 126.4 (d, J ϭ 12.3 Hz, CH-Ar), 128.5 (d, 1, toluene). The structure of 12a has been confirmed by X-ray dif-
J ϭ 15.6 Hz, CH-Ar), 129.5 (CH-Ar), 142.6 (C-Ar), 146.4 [PϪCϭ
fraction studies. The minor diastereomer (R,S)-12b was character-
1
C(CO2Me)], 148.8 [d, J ϭ 44.2 Hz, PϪC(CO2Me)], 160.4 (d, J ϭ ized only by 31P NMR (CDCl3): δ ϭ Ϫ31.4 (1JP,W ϭ 261.6,
6.8 Hz, PϪC-Ar), 164.0 [d, 2J ϭ 14.3 Hz, PϪC(CO2Me)], 164.2 [d,
2JP,H ϭ 31.8 Hz).
J ϭ 12.1 Hz, PϪCϭC(CO2Me)], 194.2 (d, 2J ϭ 8.1 Hz, WϪCOcis),
(2-{2-[(S)-4-Isopropyl-4,5-dihydro-1,3-oxazol-2-yl]phenyl}-3,4-
dimethyl-1-phosphaferrocene)W(CO)4 (13a and 13b): These com-
pounds were obtained as side products during the synthesis of
12a,b and were isolated by chromatography on silica gel. Crystals
of the major diastereomer (13b) were obtained from a hexane solu-
tion. Yield (13a and 13b): 3% (50 mg). 31P NMR (toluene): δ ϭ
Ϫ0.7 (main diastereomer), Ϫ9.6 (minor diastereomer). The struc-
ture of 13b was established by X-ray diffraction studies.
2
195.9 (d, J ϭ 30.3 Hz, WϪCOtrans).
(7-Aza-1-phosphabicyclo[2.2.1]hept-2-ene)W(CO)5 (9d): A solution
of 4d (2.0 g; 3.3 mmol) and dimethyl acetylenedicarboxylate (0.9
mL; 7.3 mmol) in 8 mL of toluene was heated under reflux for
14 h. The crude mixture was purified directly by chromatography
on silica gel with toluene as eluent. The product was dissolved in
toluene and layered with hexane. Storage of the solution at 6 °C
gave 9d as orange crystals. Yield: 54% (1.2 g). 31P NMR (CDCl3):
1
δ ϭ 32.2 (1JP,W ϭ 286 Hz). H NMR (CDCl3): δ ϭ 1.16 [s, 3 H,
(2-{2-[(S)-4-Isopropyl-4,5-dihydro-1,3-oxazol-2-yl]phenyl}-3,4-
dimethyl-1-phosphaferrocene)Mo(CO)4 (14a and 14b): To a crude
solution of 11a,b, prepared from 2 g (6.7 mmol) of 3c, was added
1 equiv. of the (MeCN)Mo(CO)5 complex [prepared from 1.76 g
(6.7 mmol) of hexacarbonylmolybdenum and 0.74 g (6.7 mmol) of
trimethylamine N-oxide in 30 mL of acetonitrile]. The solution was
stirred at room temperature for 1 h. After evaporation of the solv-
ent, the mixture was purified by chromatography on silica gel with
hexane/toluene (4:1), affording an isomeric mixture of the chelate
complexes 14a and 14b as an orange powder. Yield over two steps:
47% (1.96 g). The minor diastereomer was characterized by 31P
NMR (CDCl3): δ ϭ 8.6. The major diastereomer [(R,S)-14a] was
obtained in pure form by crystallization in hexane. (R,S)-14a: 31P
NMR (CDCl3): δ ϭ 1.5. 1H NMR (CDCl3): δ ϭ 0.86 [d, J ϭ
6.7 Hz, 3 H, CH(CH3)2], 0.93 [d, J ϭ 7.0 Hz, 3 H, CH(CH3)2], 2.27
C(CH3)2], 1.24 [s, 3 H, C(CH3)2], 3.53 (s, 3 H, OMe), 3.60 (s, 3 H,
OMe), 3.98 (AB, 2 H, OCH2), 6.92Ϫ7.14 (m, 2 H, Ar-H),
7.34Ϫ7.44 (m, 2 H, Ar-H). 13C NMR (CDCl3): δ ϭ 25.8 [d, J ϭ
6.3 Hz, C(CH3)2], 28.3 [C(CH3)2], 52.4 (OMe), 52.7 (OMe), 60.1
3
[C(CH3)2], 85.9 (d, J ϭ 4.7 Hz, OCH2), 115.0 (s, NϪC), 121.0 (d,
J ϭ 3.8 Hz, CH-Ar), 126.1 (d, J ϭ 12.2 Hz, CH-Ar), 127.7 (d, J ϭ
15.6 Hz, CH-Ar), 128.95 (CH-Ar), 145.2 (C-Ar), 149.2 [d, J ϭ
5.9 Hz, PϪCϭC(CO2Me)], 149.3 [d, J ϭ 43.8 Hz, PϪC(CO2Me)],
160.9 (d, J ϭ 5.9 Hz, PϪC(Ar)], 163.4 [d, J ϭ 14.0 Hz,
PϪC(CO2Me)], 164.1 [d, J ϭ 11.2 Hz, PϪCϭC(CO2Me)], 194.4
(d, J ϭ 8.1 Hz, WϪCOcis), 195.9 (d, J ϭ 30.2 Hz, WϪCOtrans).
C22H18NO10PW (671.19): calcd. C 39.37, H 2.70; found C 39.33,
H 2.67.
2-{2-[(S)-4-Isopropyl-4,5-dihydro-1,3-oxazol-2-yl]phenyl}-3,4-
dimethyl-1-phosphaferrocene (11a and 11b): A solution of 3c (0.73 g,
2.4 mmol) and dicarbonyl(η5-cyclopentadienyl)iron dimer (0.42 g,
1.2 mmol) in 40 mL of toluene was heated at 160 °C for 4 h under
8 bar of CO. The carbon monoxide pressure was then released and
the solution heated for additional 3 h. The solution was then al-
lowed to cool to room temperature. The final products 11a and 11b
were characterized only by 31P NMR as the crude mixture. Two
diastereomers were present in a 2:1 ratio. 31P NMR (toluene): δ ϭ
Ϫ67.1 (minor diastereomer), Ϫ68.0 (major diastereomer).
(s, 6 H, CH3), 2.80 [m, 1 H, CH(CH3)2], 3.71 (d, J
ϭ 34.0 Hz,
P,H
PϪCH), 4.05Ϫ4.20 (m, 3 H, CHN, OCH2), 4.34 (s, 5 H, Cp),
7.11Ϫ7.45 (m, 4 H, Ar-H). 13C NMR (CDCl3): δ ϭ 13.5
[CH(CH3)2], 13.9 (Me), 16.9 (d, J ϭ 2.8 Hz, Me), 18.9 [CH(CH3)2],
29.4 [CH(CH3)2], 67.4 (OCH2), 68.8 (d, J ϭ 17.5 Hz, PϪCH), 74.5
(Cp), 76.4 (CHN), 90.0 (d, J ϭ 13.1 Hz, PϪC), 92.4 (C), 94.1 (d,
J ϭ 2.6 Hz, C), 126.4 (CH-Ar), 128.4 (CH-Ar), 129.9 (CH-Ar),
130.1 (d, J ϭ 16.0 Hz), 133.1 (d, J ϭ 5.4 Hz, CH-Ar), 136.9 (d,
J ϭ 13.4 Hz, C), 169.5 (CϭN), 204.9 (d, J ϭ 12.1 Hz, COcis-P),
208.4 (d, J ϭ 10.5 Hz, COcis-P), 215.7 (d, J ϭ 47.0 Hz, COtrans-P),
219.8 (d, J ϭ 9.2 Hz, COcis-P). IR (νCO): ν˜ ϭ 2017 (m), 1895 (s),
1846 cmϪ1 (s). C27H26FeMoNO5P (627.26): calcd. C 51.70, H 4.18;
found C 51.87, H 4.05.
(µ-{2-{2-[(S)-4-Isopropyl-4,5-dihydro-1,3-oxazol-2-yl]phenyl}-3,4-
dimethyl-1-phosphaferrocene})[W(CO)5]2 (12a and 12b): A solution
of W(CO)5(THF), prepared from 1.70 g (4.8 mmol) of hexacar-
bonyltungsten in 250 mL of THF, was poured into the crude mix-
ture of 11a,b. The solution was stirred at room temperature for
0.5 h. After evaporation of the solvent, the mixture was purified by
chromatography on silica gel with toluene, affording 12a and 12b
as an orange powder. The chelate compounds 13a and 13b were
also isolated from the reaction mixture. Yield of 12a,b from 3c was
60% (1.53 g). The major diastereomer [(S,S)-12a] was obtained in
pure form after crystallization from hexane. 12a: 31P NMR
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1664
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[18]
[39d]
could lower the reactivity of the corresponding phospholes
with DMAD and thus preclude the generation of phosphinid-
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Previous syntheses of optically active phosphirane derivatives:
[19a]
A. Marinetti, L. Ricard, F. Mathey, Synthesis 1992,
[19b]
157Ϫ162.
X. Li, K. D. Robinson, P. P. Gaspar, J. Org.
Received December 7, 2001
Chem. 1996, 61, 7702Ϫ7710.
[I01502]
Eur. J. Inorg. Chem. 2002, 1657Ϫ1665
1665