The asymmetric synthesis of phosphorus- and sulfur-containing tricarbonyl(η6-arene)chromium complexes using the chiral base approach

Article abstract of DOI:10.1039/a905610f

The use of a simple chiral lithium amide base 2 enables the asymmetric transformation of tricarbonyl-[η⁶-(diphenylphosphinoyl)benzene]chromium(0) 12 into the corresponding ortho-silylated complex in up to 86% ee. A tin derivative was prepared similarly and was then used to prepare other derivatives via reduction to the corresponding phosphine, followed by transmetallation-electrophilic quench. In the case of tricarbonyl-(η⁶-1,3-dihydroisobenzothiophene)chromium(0) the chiral base 2 was ineffective, and it was necessary to use a bis-lithium amide base 9 to effect asymmetric substitution in high ee (up to 95%). Decomplexation gave the corresponding chiral sulfides in highly enantiomerically enriched form. In all cases the absolute stereochemistry of the products was derived by conducting X-ray structure determinations on selected examples. The Royal Society of Chemistry 1999.

Full text of DOI:10.1039/a905610f

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The asymmetric synthesis of phosphorus- and sulfur-containing
tricarbonyl(ꢀ6-arene)chromium complexes using the chiral base
approach
Azhar Ariffin, Alexander J. Blake, Richard A. Ewin, Wan-Sheung Li and Nigel S. Simpkins*
School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK
Received (in Cambridge, UK) 12th July 1999, Accepted 1st September 1999
The use of a simple chiral lithium amide base 2 enables the asymmetric transformation of tricarbonyl-
[η6-(diphenylphosphinoyl)benzene]chromium(0) 12 into the corresponding ortho-silylated complex in up to
86% ee. A tin derivative was prepared similarly and was then used to prepare other derivatives via reduction
to the corresponding phosphine, followed by transmetallation–electrophilic quench. In the case of tricarbonyl-
(η6-1,3-dihydroisobenzothiophene)chromium(0) the chiral base 2 was ineffective, and it was necessary to use
a bis-lithium amide base 9 to effect asymmetric substitution in high ee (up to 95%). Decomplexation gave the
corresponding chiral sulfides in highly enantiomerically enriched form. In all cases the absolute stereochemistry
of the products was derived by conducting X-ray structure determinations on selected examples.
oxide might furnish complexes with potential as chiral ligands
Introduction
for asymmetric catalysis.5
The chiral base method has turned out to be a useful way of
accessing certain types of non-racemic tricarbonyl(η6-arene)-
chromium complexes. A particularly important example is the
reaction of the anisole complex 1 with the lithium amide base 2
to give the ortho-silylated complex 3 in about 90% enantiomeric
excess, Scheme 1.1
Our chiral base work also included benzylic metallation of
complexes 5 and 6,6,7 an area of work also developed independ-
ently by Gibson and co-workers with the less conformationally
constrained analogues 7 and 8.8 In both of these two studies it
was found that the bis-lithium amide base 9 can sometimes
provide excellent levels of enantioselectivity in situations where
the simpler base 2 is inefficient.9
Aspects of this type of chiral base work have been described
in detail previously;10 the purpose of this paper is to provide full
details of our studies of the phosphorus- and sulfur-containing
complexes, 4 and 6 respectively.
Results and discussion
(i) Chemistry of phosphorus-containing systems 4
Scheme 1
Our earlier study had shown that the type of transformation
illustrated in Scheme 1 was also possible for prochiral com-
plexes having various other substituents, including carbon,
nitrogen and halogen types, but that the yields and levels of
asymmetric induction were somewhat variable.10 The presence
of an oxygen-containing function, presumably to ensure effi-
cient coordination of lithium appeared to be a prerequisite
in order to secure at least workable levels of asymmetric
induction.
Complex 3 prepared in this way has been utilised in studies of
nucleophilic addition to chiral chromium complexes, and also
in a total synthesis of (ϩ)-ptilocaulin.2,3
Analogous chiral base reactions with other types of prochiral
complexes were also examined, and an interest in enantiomeric-
ally enriched phosphines led us to examine complexes of
general formula 4.4 Thus, it was hoped that a system in which
the PXnYm group was a phosphine, phosphonate or phosphine
This apparent requirement posed a problem when dealing
with complexes having soft centres such as phosphorus or sul-
fur, and it was unclear if such systems would respond well
under chiral base conditions. We decided to explore in detail
complexes of general structure 4, and after initial studies
focused on the possibilities of using diphenylphosphine or the
corresponding phosphine oxide as the substituent. A major
factor which influenced our decision to study these systems was
the possibility to devise an easy asymmetric synthesis of novel
chiral phosphines, which might be useful ligands for asymmetric
catalysis.
Neither of the desired complexes could be prepared by the
usual protocol involving reaction of the appropriate arene with
chromium hexacarbonyl.11 This is an established problem in
the phosphine series, where the ability of phosphine ligands
to bind (via the phosphorus lone pair) to chromium is well
J. Chem. Soc., Perkin Trans. 1, 1999, 3177–3189
This journal is © The Royal Society of Chemistry 1999
3177

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established.12 In the case of triphenylphosphine oxide the oxi-
dising potential of the ligand is presumably incompatible with
the low valent chromium. We chose instead to prepare the
required systems by lithiation of the parent benzene complex
10, and reaction with appropriate phosphorus halides to give
either phosphine or phosphine oxide products, 11 or 12,
respectively, Scheme 2.13
Scheme 2 Reagents and conditions: (i) nBuLi, THF, Ϫ78 ЊC to 0 ЊC;
(ii) Ph2PCl (64%) or Ph2P(O)Cl (68%).
Fig. 1 Displacement ellipsoid plot for compound 13 [T 150 K, 50%
Preliminary chiral base studies of the phosphine 11 were dis-
appointing, producing mixtures of inseparable meta- and para-
regioisomeric products. This behaviour seems somewhat similar
to that seen with aniline complexes and, bearing in mind our
previous experience with these systems, and the advantages of
incorporating oxygen into the starting complex, we decided to
move on to the phosphine oxide system.
Pleasingly, the reaction of phosphine oxide 12 with chiral
base 2, in the presence of Me3SiCl (in situ quench) gave the
desired ortho-silylated product (Ϫ)-13 in good yield, and
with an encouraging level of asymmetric induction (73% ee),
Scheme 3.
probability, Flack parameter Ϫ0.04(4)].
At this stage the absolute configuration of the latter product
was uncertain, but we were somewhat surprised that the mono-
silylated product (Ϫ)-13 produced by 9 should be of the same
enantiomeric series as that produced by base 2, since in the past
these two bases had produced enantiocomplementary results.
This observation, along with variable levels of observed ee for
the small amounts of 13, led us to believe that a kinetic reso-
lution was responsible for the results with base 9. This possible
mechanism was subsequently demonstrated to be operative by
exposure of racemic 13 to reaction with base 9 to give the
expected products (Ϫ)-13 and (ϩ)-14, Scheme 5.
Scheme 5
The “product” 13 in the initial reaction, shown in Scheme 4,
therefore represents an unreactive enantiomer in a stereo-
determining step involving meta-silylation, and answers the
concern that the reactions shown in Schemes 3 and 4 should not
generate the same enantiomeric series. The potential of base 9
for over-silylation had not been a problem in earlier work, and
we decided not to pursue this area further.
Surprisingly, when we attempted to carry out asymmetric
substitution of 12 with electrophiles other than Me3SiCl, such
as MeI, D2O, PhCHO, etc. no products were obtained, even in
the presence of LiCl (one exception is Bu3SnCl, which is dis-
cussed in detail later on). This result is perplexing, but mirrors a
similar experience with a related metallation of a phosphinoyl-
substituted ferrocene.14 One possible explanation is that with
Me3SiCl there is a particularly strong interaction with the
Scheme 3
Crystallisation of a typical non-racemic sample of (Ϫ)-13
from hexane allowed separation of the more highly crystalline
racemate, leaving ≥50% yield of 13 in enantiomerically pure
form. Further crystallisation from hexane then enabled an
X-ray structure determination, which allowed the assignment
of absolute configuration as shown in Fig. 1. Significantly, the
sense of asymmetric induction in the reaction leading to 13 is
opposite to that seen in our earlier work, e.g. in the synthesis of
3, vide infra.
By reducing the reaction temperature to Ϫ100 ЊC it was pos-
sible to increase the ee of the product complex to 86%. How-
ever, other mono-lithium amide bases gave lower levels of
induction, and this led us to attempt the metallation with bis-
lithium amide base 9. In this case we observed only small
amounts of the anticipated mono-silylated complex (Ϫ)-13, the
major product being the disilylated product (ϩ)-14, with an ee
of 82%, Scheme 4.
polarised oxygen of the P᎐O bond (the most extreme represen-
᎐
tation would be actual O-silylation), which activates the system
towards metallation, and which is not possible with the other
electrophiles.
With direct access to other substituted complexes denied our
other options were to either substitute at the remaining ortho-
position of 13 and then remove the silicon blocking group or
attempt ipso-type replacement of the silicon group, for example
using fluoride-mediated substitution reactions. Both of these
avenues were explored, with little success. Complex 13 appears
resistant to a second metallation using either alkyllithium or
lithium amide bases, perhaps due to shielding of the remaining
ortho-hydrogen by the phenyl groups of the phosphinoyl sub-
stituent. This effect is due to the conformation enforced on the
phosphinoyl group due to the presence of the silicon substitu-
Scheme 4
3178
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Table 1
Electrophile
Me3SiCl
PhCHO
RCHOa
PhCOCl
MeI
EtI
BnBr
(BrCF2)2
Productb
Yield (%)
18
80
21
83
22
70
23
70
24
67
25
53
26
31
27
61
a R = cyclohexyl. b All (Ϫ)-isomers.
ent, as seen in the X-ray structure, Fig. 1. Fluoride mediated
substitution of 13, employing Bu4NF or CsF,15 gave the desired
adduct only with PhCHO, and alternative electrophiles did not
give good results. At this point the prospect of preparing varied
chiral complexes via asymmetric metallation of 12 appeared
somewhat bleak.
phosphinoyl group to give the simple stannylated complex 17,
and attempted Stille type reactions were also unsuccessful.
In order to progress this chemistry it was decided to reduce
the phosphine oxide 16 to give the corresponding phosphine.
This transformation was achieved using a mixture of polymeth-
ylhydrosiloxane and Ti(OPr)4 in THF at reflux, Scheme 7.17
One further aspect of this work was confusing. Whereas bis-
lithium amide base 9 was capable of metallating 13, as shown in
Scheme 5, we were unable to carry out this second metallation
using other types of base, including 2. However, if the starting
complex was treated straightaway with excess 2, then we did
observe formation of (Ϫ)-14, Scheme 6.
Scheme 7
As shown, not only (Ϫ)-16, but also complexes 13 and 14 (as
their racemates) were also cleanly reduced to the corresponding
phosphines using this method.
Scheme 6
A re-investigation of the transmetallation approach, this time
with phosphine complex (Ϫ)-20, proved much more fruitful
than with the corresponding phosphine oxide, Table 1.
The use of cyclohexanecarbaldehyde as quenching agent gave
the desired adducts 22 as a 9:1 mixture of diastereomers,
whereas the corresponding reaction with benzaldehyde gave
only one detectable stereoisomeric product 21. This latter com-
These apparently contradictory results seem to indicate
that (Ϫ)-14, formed using base 2, cannot be formed via the
intermediate mono-silylated complex 13. We therefore propose
that this reaction proceeds via an intermediate dianion 15, as
shown in Scheme 6, a type of intermediate previously demon-
strated to be formed in the metallation of sulfinyl-substituted
complexes.16
A breakthrough in our efforts to obtain further types of sub-
stituted complex was the finding that chiral base reaction of 12
with base 2 (at Ϫ100 ЊC) in the presence of Bu3SnCl gave the
ortho-stannylated complex 16 in excellent yield (98%). The use
pound was shown to have the relative stereochemistry shown in
Fig. 2 by X-ray structure determination,† and was assayed by
HPLC and found to have an ee of 81%. We assume that this
level of induction reflects that for the initial stannane inter-
mediate (Ϫ)-16, and also the other products indicated in Table
1. This level of induction is in line with, but perhaps slightly
lower than, that seen earlier in the generation of 13 under the
same conditions.
The availability of stannylated complexes also suggested the
possibility of Stille type couplings to give biaryl complexes.
However, initial attempts in this area using complex 16 were not
fruitful, and we turned instead to the use of the ortho-bromo-
phosphine complex 27 in Suzuki cross-coupling reactions.
of tin halides as in situ quenching agents for anions seems not
to have been described explicitly before, and in this case the
reagent presumably performs the crucial activation of the sys-
tem towards metallation, as discussed above for Me3SiCl. At
this point the stannane product was assumed to have the same
ee as the silylated chiral base product 13 (ca. 85% ee), but this
could not be verified until further transformations had been
carried out.
With stannane 16 in hand, obvious avenues to explore
included transmetallation and cross-coupling reactions. How-
n
ever, reaction of 16 with BuLi resulted only in cleavage of the
† This determination was carried out using racemic material.
J. Chem. Soc., Perkin Trans. 1, 1999, 3177–3189
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those on the phosphorus atom. Although this model is simply
a crude pictorial representation of the observed selectivity, it
serves to explain a body of results involving enantioselective
enolisation of cyclic ketones of varied structures, as well as
deprotonation of certain other types of substrate.19 In this
regard, it is the reaction of complex 1 with base 2 that seems not
to fit this simple model. Although we were in no doubt concern-
ing the earlier results, this apparent disparity prompted us to
correlate the anisole complex chemistry with the present work
on phosphinoyl complex 12. This was done as outlined in
Scheme 9.
Fig. 2 Displacement ellipsoid plot for compound 21 [T 150 K, 50%
probability].
Scheme 9 Reagents and conditions: (i) NaOMe, 15-C-5, THF, ∆ (61%);
(ii) nBuLi, THF, Ph2PCl (78%); (iii) TBAF, THF, Ϫ78 ЊC (95%).
Substitution of bromine in the complex (Ϫ)-27 gave the
o-methoxyphosphine complex (Ϫ)-31. This same compound
could also be prepared starting with (ϩ)-3 by metallation and
reaction with Ph2PCl, followed by desilylation with tetrabutyl-
ammonium fluoride (TBAF). In this case the product was
(ϩ)-31, which was the expected outcome based on the original
assignments.
The chemistry described above enables the synthesis of
varied phosphorus-containing complexes in good enantiomeric
excess. The crystallinity of many of these systems allows facile
enantiomeric enrichment, thus allowing access to enantio-
merically pure derivatives. Although we have been unable to
explore this area further, the potential for these types of com-
plex for asymmetric catalysis has been highlighted in a recent
review by Bolm and Muniz.5a
Fig. 3
Under usual Suzuki reaction conditions coupling of this
substrate with typical arylboronic acids was achieved in high
yield to give biaryl complexes 28–30, Scheme 8.18
(ii) Chemistry of sulfur-containing system 6
The effective asymmetric substitution of complex 6 was dem-
onstrated to require the use of bis-lithium amide 9 to achieve
high enantiomeric excess, the use of the simpler base 2 giving
products of only about 5% ee.7 Initial reactions using base 9
in the presence of Me3SiCl (in situ quench) gave the desired
product 32 in 95% yield, and with an ee of 89%.
Scheme 8
This type of reaction sequence serves to generate product
complexes not available by other means, for example by the
transmetallation–electrophilic quench sequence, including the
interesting thiophene derivative 30.
To conclude this chiral base study of complex 12 we
reconsidered the sense of enantioselectivity observed in the
initial reaction with chiral base 2 and how this compares to our
earlier work with anisole complex 1. The present results with
complex 12 conform to a naive model in which approach of the
substrate to the chiral lithium amide occurs as shown in Fig. 3.
In Fig. 3a approach of the chromium complex to the chiral
base occurs via an open quadrant, and coordination of the
phosphine oxide to the lithiated base then allows removal of
the ring hydrogen shown. In the case of removal of the enantio-
However, analogous reactions using base 9, but with MeI as
the electrophile, gave little or no product. As in our previous
work,10 this result was shown to be due to a salt in which LiCl,
either generated from the Me3SiCl or added deliberately, sub-
stantially accelerates the rate of metallation. In this case reac-
tion with base 9 followed by D2O quenching gave no deuterium
incorporation, whereas the corresponding reaction including
0.5–1.0 equivalents of LiCl showed ca. 95% incorporation.
topic hydrogen, shown in Fig. 3b, placing both the P᎐O and the
᎐
hydrogen to be removed in the vicinity of the basic nitrogen
results in steric clashes between a phenyl group on the base and
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Table 2
Electrophile
Me3SiCl
MeI
EtI
BnBr
Ph2CO
allylBr
ArCH2Bra
Product
Yield (%)
Ee (%)b
32
95
89
33
95
94
34
35
36
88
95
37
38
89
95
91
70
75
87c
n.d.d
n.d.d
a ArCH2Br = 2-(bromomethyl)naphthalene. b Determined by HPLC. c Sluggish alkylation at Ϫ78 ЊC may account for slightly lower ee. d Not
determined (ee assay not readily established).
Finally, we observed some variations in apparent rates of
electrophilic quench, depending upon which type of base is
used for the metallation. The best base for preparing racemic
t
compounds (for ee assay) was BuLi, with other bases giving
lower yields due to the formation of polysilylated by-products.
Reaction with tBuLi, followed by quenching with EtI or benzyl
bromide, gave moderate yields of alkylated products (45–65%)
after one hour at Ϫ100 ЊC, whereas analogous reactions using
base 9 gave only traces of product. We attribute this effect to
complexation of the intermediate anion with the monoanion
corresponding to 9—i.e. the anionic chromium complex forms
a mixed aggregate with the mono-lithium amide, which reduces
the rate of subsequent electrophilic quench. Another con-
sequence of this effect is in the reaction with acetone. Using
tBuLi as the base gives 83% yield of the acetone adduct,
whereas use of 9 gives only about 20% yield (although the ee is
Fig. 4 Displacement ellipsoid plot for compound 33 [T 150 K, 50%
probability, Flack parameter Ϫ0.02(2)].
99%!), presumably because the mixed aggregate is highly basic
and promotes aldolisation of the acetone.
With some of the complexes, i.e. 32, 33, 36 and 38, it was
Subsequently, by including LiCl into the reaction medium, we
were able to conduct highly enantioselective metallations, and
quench with a range of electrophiles, Table 2.
As shown, it was possible to determine the levels of ee for
several of the products, these being good to excellent. The abso-
lute stereochemistry of the products is based on an X-ray struc-
ture determination carried out on the methylated product 33
following recrystallisation, Fig. 4.
possible to improve the level of enantiomeric enrichment to
>99% ee by recrystallisation. Finally, some of the complexes
were exposed to light, in the presence of atmospheric oxygen, in
order to effect demetallation and enable the isolation of the
corresponding free sulfides 39–43 in highly enantiomerically
enriched form.
The sense of asymmetric induction is as expected from our
previous work on the corresponding isobenzofuran complex 5,6
the bis-amide 9 giving opposite selectivity to the simpler amide
2 (both prepared from (R)-phenylethylamine). Interestingly,
Gibson and co-workers observed a swap-over in the sense of
absolute stereochemical outcome in the asymmetric synthesis
of sulfur-containing complexes starting with 8 compared to
ethers derived from 7, using base 9.8 This unexpected observ-
ation is not duplicated in our results, presumably due to the
additional conformational constraint imposed by incorporating
the heteroatom into a ring structure.
Several further points relating to the chiral base reactions of
this system are worthy of mention. Firstly, although the pres-
ence of LiCl is essential to promote metallation, it seems not to
affect the enantioselectivity of the process; traces of product
formed in the absence of salt were still of very high ee. Sec-
ondly, reactions can be conducted using the mono-lithium
amide corresponding to 9—i.e. the base generated when the
diamine precursor is treated with only one equivalent of nBuLi.
In this case products are formed with comparable ee to when 9
is used, but in somewhat lower yields. This finding is in agree-
ment with those of Gibson and co-workers, although in their
system they found that even the yields of highly enriched
products were not adversely affected by reducing the amount of
nBuLi used to one equivalent.20
Chiral sulfides have recently found use in a range of asym-
metric transformations, including epoxidation, sulfenylation
and cuprate addition reactions.21–23 It is hoped that our new
family of chiral sulfides, along with the respective chromium
complexes, may open up new possibilities for the design of
novel sulfur-containing reagents and catalysts.
Conclusion
The use of chiral lithium amide bases can provide an easy
access to a wide range of chiral products in highly enantio-
merically enriched form. In the present work we have sought
to apply this strategy to some unusual tricarbonyl(η6-arene)-
chromium complexes containing phosphorus and sulfur.
Hopefully the results will encourage others to use the chiral
base method in the organometallic arena, and the types
of chiral phosphine and sulfide that we have described
here may yet prove to have applications in asymmetric
catalysis.
J. Chem. Soc., Perkin Trans. 1, 1999, 3177–3189
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an atmosphere of nitrogen. The reaction mixture was warmed
Experimental
to 0 ЊC and stirred for 0.25 h before being recooled to Ϫ78 ЊC.
This solution was added dropwise by cannula to a solution of
diphenylphosphinic chloride (1.70 ml, 8.91 mmol) in THF (10
ml) at Ϫ78 ЊC. Stirring was continued at Ϫ78 ЊC for an addi-
tional 1 h before the reaction mixture was quenched with satur-
ated aqueous NaHCO3 (5 ml) and allowed to warm to room
temperature. The reaction mixture was then extracted with
ethyl acetate (2 × 30 ml), and the combined organic extracts
were washed with water (50 ml) and brine (50 ml), dried
(MgSO4), and evaporated under reduced pressure. Purification
of the resulting yellow oil by flash column chromatography on
silica (40% EtOAc–light petroleum) gave complex 12 as a
yellow solid (1.21 g, 62%), mp 157–158 ЊC (Found: C, 61.07; H,
3.59. C21H15O4PCr requires C, 60.88; H, 3.65%); νmax (CHCl3)/
General details
Melting points were determined using a hot-stage melting point
apparatus and are uncorrected. Infrared (IR) spectra were
recorded using a Perkin-Elmer 1600 Series FTIR spectrometer.
Mass spectra were recorded on an AEI MS-902 or VG
Micromass 70E mass spectrometer, using electron impact ion-
isation (EI) or fast atom bombardment (FAB) using m-nitro-
benzyl alcohol as the matrix. Microanalytical data were
obtained on a Perkin-Elmer 240B elemental analyser. Optical
rotations were recorded using a JASCO DIP370 digital
polarimeter.
All NMR spectra were recorded on either a Bruker AM 250,
JEOL FX 270, Bruker AM 400 or Bruker AM 500 spec-
trometer, with tetramethylsilane as internal standard. J values
are recorded in Hz and assignments indicated for 13C NMR
were obtained with the aid of a DEPT sequence.
Flash column chromatography was performed using Fluka
silica gel 60 (220–440 mesh). Analytical TLC was performed
using MACHEREY-NAGEL Polygram SIL G/UV254 silica gel
precoated plastic plates which were viewed under ultraviolet
light and developed with basic potassium permanganate solu-
tion. Enantiomeric excesses were determined by high perform-
ance liquid chromatography (HPLC) using either Chiralcel OD
or OJ columns at ambient temperatures. Detection was by UV
at the stated wavelength and data was processed using an
HP-3D Dos chemstation.
cmϪ1 1991 and 1934 (C᎐O); δ (250 MHz, CDCl ) 5.09 (2H, m,
᎐
᎐
H
3
CrCH), 5.60–5.66 (3H, m, CrCH), 7.47–7.64 (6H, m, ArH)
and 7.70–7.79 (4H, m, ArH); δC (68 MHz, CDCl3), 87.4 [d, JP-C
9, 2CrCH], 94.3 (d, JP-C 102, CrC), 95.5 (CrCH), 96.7 (d, JP-C
10, 2CrCH), 128.4 (d, JP-C 12, 4ArCH), 130.3 (2ArC), 131.7
(d, JP-C 10, 4ArCH), 132.4 (d, JP-C 3, 2ArCH) and 230.3
(3CO); m/z (FAB) 415 [(M ϩ H)ϩ, 20%], 358 [(M Ϫ 2CO)ϩ,
17%], 330 [(M Ϫ 3CO)ϩ, 100%] (HRMS: found [M ϩ H]ϩ,
415.0236. Requires [M ϩ H], 415.0191).
Synthesis of (2S)-tricarbonyl[ꢀ6-(1-diphenylphosphinoyl-2-
trimethylsilyl)benzene]chromium(0) 13 according to Scheme 3
A solution of the chiral base 2 (ϩLiCl) was prepared by addi-
tion of n-BuLi (3.9 ml of 1.6 M solution in hexanes, 6.2 mmol)
to a solution of the appropriate chiral amine hydrochloride salt
(758 mg, 2.90 mmol) in THF (30 ml) at Ϫ78 ЊC, under an
atmosphere of nitrogen. The solution was warmed to room
temperature and stirred for 0.25 h before being recooled to
Ϫ78 ЊC, and Me3SiCl (1.5 ml, 12 mmol) was added in one por-
tion, followed by a solution of the chromium complex 12 (1.0 g,
2.4 mmol) in THF (3 ml). After stirring the solution at Ϫ78 ЊC
for 0.5 h, saturated aqueous NaHCO3 (5 ml) was added and the
mixture was then allowed to warm to room temperature. The
mixture was extracted with diethyl ether (30 ml), the organic
extract was washed with dilute HCl (2 M, 30 ml), dried
(MgSO4), and evaporated under reduced pressure. The resulting
yellow oil was then purified by flash column chromatography
on silica gel (25% EtOAc–light petroleum) to give the silylated
complex 13 (1.05 g, 90%), mp 156–157 ЊC; [α]D22 Ϫ203 (c 0.36 in
CHCl3) (Found: C, 59.29; H, 4.94. C24H23O4PSiCr requires C,
59.25; H, 4.77%); νmax (CHCl3)/cmϪ1 1990, 1935 and 1872
Organic solvents and reagents were dried by distillation from
the appropriate drying agents. THF and Et2O were distilled
over sodium wire–benzophenone ketyl, methanol from mag-
nesium methoxide and chlorotrimethylsilane from calcium
hydride. Light petroleum refers to light petroleum (bp 40–
60 ЊC) which was distilled prior to use. Unless otherwise stated,
all other solvents and reagents were used as received from
commercial suppliers.
Tricarbonyl[ꢀ6-(diphenylphosphino)benzene]chromium(0)] 1113
n-BuLi (3.5 ml of a 1.6 M solution in hexanes, 5.6 mmol) was
added dropwise to a solution of tricarbonyl(η6-benzene)-
chromium(0) 10 (1.00 g, 4.7 mmol) in THF (25 ml) at Ϫ78 ЊC
under an atmosphere of nitrogen. The reaction mixture was
warmed to 0 ЊC and stirred for 0.25 h before being recooled to
Ϫ78 ЊC. This solution was added dropwise by cannula to a solu-
tion of chlorodiphenylphosphine (1.70 ml, 9.47 mmol) in THF
(10 ml) at Ϫ78 ЊC. Stirring was continued at Ϫ78 ЊC for an
additional 1 h before the reaction mixture was quenched with
saturated aqueous NaHCO3 (5 ml) and allowed to warm to
room temperature. The reaction mixture was then extracted
with ethyl acetate (2 × 30 ml), and the combined organic
extracts were washed with water (50 ml), and brine (50 ml),
dried (MgSO4), and evaporated under reduced pressure. Purifi-
cation of the resulting yellow oil by flash column chromato-
graphy on silica gel (20% EtOAc–light petroleum) gave complex
11 as a yellow solid (1.0 g, 54%), mp 147–148 ЊC (lit.,13 146–
147 ЊC); νmax (CHCl3)/cmϪ1 1979 and 1897 (C᎐O); δ (250 MHz,
᎐
(C᎐O); δ (250 MHz, CDCl ) 0.31 (9H, s, SiMe ), 4.84 (1H, dd,
᎐
H
3
3
3JP(O)-H 10 and 3JH-H 6, CrCH), 5.27 (1H, dd, J 6, CrCH), 5.43
(1H, dd, J 6, CrCH), 5.55 (1H, d, J 6, CrCH) and 7.46–7.74
[10H, m, (ArH)2P]; δC (68 MHz, CDCl3) 2.3 (Si(CH3)3), 91.4 (d,
JP-C 11, CrCH), 93.1 (CrCH), 96.2 (d, JP-C 15, CrCH), 98.7 (d,
JP-C 11.00, CrCH), 101.5 (d, JP(O)-C 104, CrC), 105.8 (d, JP-C 15,
CrC), {(128.7, 128.9, 129.1), ArCH}, 131.7 (d, JP-C 48, ArC),
{(132.2, 132.4, 132.5, 132.6, 132.8, 132.9, 133.1), ArCH}, 134.0
(d, JP-C 102, ArC) and 231.1 (3CO); m/z (FAB) 486 (Mϩ, 6%),
402 [(M Ϫ 3CO)ϩ, 48%] and 335 [(M Ϫ Cr(CO)3 Ϫ CH3)ϩ,
100%] (HRMS: found [M ϩ H]ϩ, 487.0647. Requires [M ϩ H],
487.0587).
᎐
H
CDCl3) 5.18 (4H, m, CrCH), 5.44 (1H, m, CrCH), 7.39 (10H,
m, ArH); δC (68 MHz, CDCl3) 91.9 (d, JP-C 5, 2CrCH), 95.0
(CrCH), 99.5 (d, JP-C 17, 2CrCH), 104.0 (d, JP-C 20, CrC), 130.0
(d, JP-C 7, ArCH), 130.7 (ArCH), 135.2 (d, JP-C 7, ArCH), 136.2
(d, JP-C 12, ArC) and 233.3 (3CO); m/z (EI) 398 (Mϩ, 3%), 314
The enantiomeric excess of 13 was determined to be 73%
using a Chiralcel OD column with 99.5:0.5 hexane–isopropyl
alcohol (IPA) as eluent. Flow rate 1 ml minϪ1. Detection 256 nm.
Retention times 33.7 min (major) and 39.7 min (minor).
[(M Ϫ 3CO)ϩ, 100%], 262 [(M Ϫ Cr(CO)3)ϩ 50%] and 183
,
[(M Ϫ Cr(CO)3 Ϫ Ph)ϩ, 31%] (HRMS: found Mϩ, 398.0174.
C21H15O3PCr requires M, 398.0164).
Synthesis of (2S)-tricarbonyl{ꢀ6-[1-diphenylphosphinoyl-2,5-
bis(trimethylsilyl)]benzene}chromium(0) 14 using 2 equiv. of
chiral base 2 according to Scheme 6
Tricarbonyl[ꢀ6-(diphenylphosphinoyl)benzene]chromium(0) 12
n-BuLi (3.5 ml of a 1.6 M solution in hexanes, 5.6 mmol) was
added dropwise to a solution of tricarbonyl(η6-benzene)-
chromium(0) (1.0 g, 4.7 mmol) in THF (25 ml) at Ϫ78 ЊC under
A solution of chiral base 2 was prepared, as described above,
using chiral amine hydrochloride salt (1.52 g, 5.80 mmol) and
n-BuLi (8.3 ml of 1.6 M solution in hexanes, 13 mmol), in THF
3182
J. Chem. Soc., Perkin Trans. 1, 1999, 3177–3189

View Article Online
(100 ml). To the resulting solution of the chiral base 2 (ϩLiCl)
at Ϫ78 ЊC was added Me3SiCl (4.0 ml, 31 mmol) in one portion,
followed by a solution of the chromium complex 12 (1.20 g,
2.90 mmol) in THF (3 ml). After stirring the solution at Ϫ78 ЊC
for 0.5 h, saturated aqueous NaHCO3 (5 ml) was added and the
mixture was allowed to warm to room temperature. The mix-
ture was extracted with diethyl ether (2 × 30 ml), and the com-
bined organic extracts were washed with dilute HCl (2 M,
2 × 30 ml), dried (MgSO4), and evaporated under reduced pres-
sure. The resulting yellow oil was then purified by flash column
chromatography on silica gel (10–25% EtOAc–light petroleum)
to give the disilylated complex 14 as a yellow solid (1.33 g,
82%), mp 172 ЊC; [α]D22 Ϫ162 (c 1.0 in CHCl3) (Found: C, 57.92;
H, 5.65. C27H31O4PSi2Cr requires C, 58.06; H, 5.60%); νmax
NaHCO3 (3 ml) was added. After addition of EtOAc (5 ml), the
organic layer was separated and washed with saturated aqueous
NaHCO3 (10 ml), brine (10 ml), and dried (MgSO4). The sol-
vent was evaporated under reduced pressure and the resulting
yellow residue was purified by flash column chromatography on
silica gel (10–25% EtOAc–light petroleum) to give 14 as a yel-
low solid (22 mg, 46%), mp 171 ЊC; [α]D20 110 (c 0.45 in CHCl3)
and 13 as a yellow oil (15 mg, 36%), [α]D20 Ϫ148 (c 0.72 in CHCl3).
Both complexes were identified by their 1H NMR spectra,
which were identical to those descibed above. The ee values
for these samples of 14 and 13 were determined, as described
above, to be 64% and 73% respectively.
(2R)-Tricarbonyl[ꢀ6-(1-diphenylphosphinoyl-2-tributylstannyl)-
benzene]chromium(0) 16
(CHCl3)/cmϪ1 1982 and 1923 (C᎐O); δ (250 MHz, CDCl ) 0.14
᎐
᎐
H
3
(9H, s, Si(CH3)3), 0.32 (9H, s, Si(CH3)3), 4.94 (1H, dd, 3JP(O)-H 10
and J 1, CrCH), 5.38 (1H, dd, J 6 and JP-H 2, CrCH), 5.52 (1H,
ddd, J 6, JP-H 2 and J 1, CrCH) and 7.46–7.73 [10H, m,
(ArH)2P]; δC (68 MHz, CDCl3) Ϫ0.4 (Si(CH3)3), 3.0 (Si(CH3)3),
97.7 (d, J 10, CrCH), 98.9 (d, J 7, CrC), 100.0 (d, JP(O)-C 105,
CrC), 100.1 (CrCH), 103.2 (d, J 13, CrCH), 109.0 (d, J 15,
CrC), {(129.4, 129.5, 129.6, 129.7, 129.9), ArCH}, {(133.1,
133.3, 133.3, 133.3, 133.5, 133.6), ArCH}, 134.5 (d, JP(O)-C
101, ArC) and 232.5 (3CO); m/z (FAB) 559 [(M ϩ H)ϩ,
30%] (HRMS: found [M ϩ H]ϩ, 559.0999. Requires [M ϩ H],
559.0982).
A solution of chiral base 2 was prepared, as described above,
using chiral amine hydrochloride salt (473 mg, 1.81 mmol) and
n-BuLi (2.25 ml, 1.6 M solution in hexanes, 3.60 mmol) in THF
(15 ml). The resulting solution of chiral base 2 (ϩLiCl) was
cooled to Ϫ100 ЊC, and a mixture of Bu3SnCl (2.00 ml, 7.37
mmol) and complex 12 (624 mg, 1.51 mmol) in THF (5 ml), was
added in one portion. After stirring at Ϫ100 ЊC for 0.5 h, satur-
ated aqueous NaHCO3 (5 ml) was added and the mixture
was allowed to warm to room temperature. The mixture was
extracted with diethyl ether (30 ml), and the organic extract was
washed with dilute HCl (2 M, 30 ml) and stirred with aqueous
ammonia (5% v/v, 100 ml) for 16 h. The organic layer was sep-
arated, dried (MgSO4), and evaporated under reduced pressure.
The resulting yellow oil was then purified by flash column
chromatography on silica gel (20% EtOAc–light petroleum) to
yield complex 16 as a yellow solid (1.03 g, 98%), mp 128 ЊC; [α]D22
Ϫ86 (c 2.4 in CHCl3) (Found: C, 56.40; H, 6.04. C33H41O4P-
The enantiomeric excess of 14 was found to be 79% using a
Chiralcel OD column with 99.5:0.5 hexane–IPA as eluent.
Flow rate 1 ml minϪ1. Detection 256 nm. Retention times 15.2
min (major) and 16.23 min (minor).
Synthesis of (2R)-tricarbonyl{ꢀ6-[1-diphenylphosphinoyl-2,5-
bis(trimethylsilyl)]benzene}chromium(0) 14 using chiral base 9
according to Scheme 4
SnCr requires C, 56.35; H, 5.87%); νmax (CHCl3)/cmϪ1 1974 and
᎐
1908 (C᎐O); δH (250 MHz, CDCl3) 0.85 (9H, t, J 7, Sn[(CH2)3-
᎐
A solution of the bis-lithium amide base 9 was prepared by
addition of n-BuLi (0.40 ml of a 1.45 M solution in hexanes,
0.58 mmol) dropwise to a solution of the corresponding chiral
diamine (0.12 g, 0.29 mmol) in THF (10 ml) at Ϫ78 ЊC under an
atmosphere of nitrogen. The mixture was allowed to warm to
room temperature and stirred for 0.25 h before it was recooled
to Ϫ78 ЊC. Chlorotrimethylsilane (0.15 ml, 1.20 mmol) was
added in one portion followed by complex 12 (0.10 g, 0.24
mmol) in THF (1 ml). The reaction mixture was allowed to stir
at Ϫ78 ЊC for 0.5 h before saturated aqueous NaHCO3 (3 ml)
was added. After addition of EtOAc (5 ml), the organic layer
was separated and washed with saturated aqueous NaHCO3 (10
ml), brine (10 ml), and dried (MgSO4). The organic extract was
concentrated under reduced pressure and the resulting yellow
residue was purified by flash column chromatography on silica
gel (10–25% EtOAc–light petroleum) to give 14, as a yellow
solid (80 mg, 59%), mp 170 ЊC; [α]D20 160 (c 0.64 in CHCl3) and 13
as a yellow oil (8 mg, 7%); [α]D20 Ϫ119 (c 0.13 in CHCl3). Both
complexes were identified by their 1H NMR spectra, which were
identical to those described above. The ee of 14 was deter-
mined, as described above, to be 82%.
CH3]3), 1.09 (6H, m, Sn[(CH2)3CH3]3), 1.17–1.31 (6H, m, Sn-
[(CH2)3CH3]3), 1.37–1.49 (6H, m, Sn[(CH2)3CH3]), 5.08–5.14
(1H, m, CrCH), 5.18–5.24 (1H, m, CrCH), 5.40 (1H, d, J 6,
CrCH), 5.46–5.53 (1H, m, CrCH) and 7.43–7.76 [10H, m,
(ArH)2P]; δC (68 MHz, CDCl3) 13.3 (3CH2), 13.6 (3CH3), 27.4
(3CH2), 28.9 (3CH2), 89.7 (d, JP-C 11, CrCH), 95.4 (CrCH),
96.4 (d, JP-C 16, CrCH), 97.7 (d, JP-C 13, CrCH), 100.1 (d, JP-C
110, CrC), 107.7 (d, JP-C 16, CrC), {(128.2, 128.4, 128.6),
ArCH}, 130.8 (d, JP-C 106, ArC), {(131.7, 131.9, 132.2, 132.3,
132.5, 132.5), ArCH}, 134.0 (ArC) and 231.3 (3CO); m/z (FAB)
703 (Mϩ, 1%), 647 [(M Ϫ Bu)ϩ, 100%] and 619 [(M Ϫ 3CO)ϩ,
7%] (HRMS: found [M Ϫ Bu]ϩ, 647.0405. Requires [M Ϫ Bu],
647.0465).
Reduction of phosphine oxides according to Scheme 7
(i) Preparation of tricarbonyl[ꢀ6-(1-diphenylphosphino-2-
trimethylsilyl)benzene]chromium(0) 18. To a mixture of complex
13 (0.11 g, 0.23 mmol) and polymethylhydrosiloxane (0.15 ml,
2.30 mmol of H equiv.) in THF (2 ml) was added Ti(OiPr)4
(0.068 ml, 0.23 mmol) and the mixture was heated at reflux
overnight. The reaction mixture was cooled to room temper-
ature and diluted with THF (20 ml). NaOH solution (2 M, 100
ml) was added slowly with vigorous stirring and the mixture
stirred for 8 h. The mixture was extracted with ethyl acetate
(2 × 20 ml). The combined organic extracts were washed with
dilute HCl (2 M, 10 ml), brine (2 × 20 ml), dried (MgSO4) and
evaporated under reduced pressure. The product was purified
by flash column chromatography on silica gel (10% EtOAc–
light petroleum) to give complex 18 as a yellow crystalline solid
(80 mg, 74%), mp 193 ЊC (Found: C, 60.94; H, 5.11. C24H23-
Synthesis of (2S)-tricarbonyl[ꢀ6-(1-diphenylphosphinoyl-2-
trimethylsilyl)benzene]chromium(0) 13 and (2R)-tricarbonyl-
{ꢀ6-[1-diphenylphosphinoyl-2,5-bis(trimethylsilyl)]benzene}-
chromium(0) 14 via kinetic resolution of ( )-13 according to
Scheme 5
A solution of chiral base 9 was prepared, as described above,
using chiral diamine (43 mg, 0.10 mmol) and n-BuLi (0.13 ml
of a 1.6 M solution in hexanes, 0.21 mmol) in THF (5 ml).
The resulting solution of 9, at Ϫ78 ЊC, was added dropwise
by cannula to a solution of ( )-13 (42 mg, 0.086 mmol) and
chlorotrimethylsilane (0.05 ml, 0.43 mmol) in THF (5 ml) at
Ϫ78 ЊC under an atmosphere of nitrogen. The reaction mixture
was allowed to stir at Ϫ78 ЊC for 0.5 h before saturated aqueous
O3SiPCr requires C, 61.27; H, 4.93%); νmax (CHCl3)/cmϪ1 1969
᎐
and 1902 (C᎐O); δ (250 MHz, CDCl3) 0.28 [9H, s, Si(CH3)3];
᎐
H
4.71 (1H, ddd, J 6 and 2, CrCH), 5.27–5.39 (2H, m, CrCH),
5.44 (1H, ddd, J 6 and 2, CrCH) and 7.22–7.37 [10H, m,
(ArH)2P]; δC (68 MHz, CDCl3) 1.4 [Si(CH3)3], 92.0 (CrCH),
J. Chem. Soc., Perkin Trans. 1, 1999, 3177–3189
3183

View Article Online
93.4 (CrCH), 95.6 (CrCH), 99.4 (d, JP-C 12, CrCH), 106.6
(d, JP-C 29, CrC), 110.7 (d, JP-C 21, CrC), {(128.5, 128.7,
128.9, 129.6, 133.2, 133.5), ArCH}, 134.3 (d, JP-C 15, ArC),
{(134.6, 134.9), ArCH}, 137.2 (d, JP-C 10, ArC) and 232.4
(3CO); m/z (EI) 470 (Mϩ, 1%), 386 [(M Ϫ 3CO)ϩ, 100%] and
334 [(M Ϫ 3CO Ϫ Cr)ϩ, 32%] (HRMS: found Mϩ, 470.0587.
Requires M, 470.0559).
at Ϫ78 ЊC under an atmosphere of nitrogen. The reaction mix-
ture was stirred at Ϫ78 ЊC for 0.5 h before addition of chloro-
trimethylsilane (0.089 ml, 0.70 mmol) in one portion and the
mixture was stirred at Ϫ78 ЊC for a further 0.25 h. The reaction
mixture was quenched with saturated aqueous NaHCO3 (1 ml),
allowed to warm up to room temperature and extracted with
ethyl acetate (3 × 10 ml). The combined organic extracts were
washed with water (2 × 10 ml), dried (MgSO4), and the solvent
was evaporated under reduced pressure. The resulting yellow
residue was purified by flash column chromatography on silica
gel (5% EtOAc–light petroleum) to give complex 18 as a yellow
solid (53 mg, 80%); [α]D24 Ϫ289 (c 0.40 in CHCl3). The 1H NMR
spectrum of the product was identical to that described above.
(ii) Preparation of tricarbonyl{ꢀ6-[1-diphenylphosphino-2,5-
bis(trimethylsilyl)]benzene}chromium(0) 19. To a mixture of
complex 14 (0.10 g, 0.18 mmol) and polymethylhydrosiloxane
(0.12 ml, 1.80 mmol of H equiv.) in THF (5 ml) was added
Ti(OiPr)4 (0.053 ml, 0.18 mmol) and the mixture was heated
at reflux overnight. The reaction mixture was cooled to room
temperature and diluted with THF (20 ml). NaOH solution
(2 M, 100 ml) was added slowly with vigorous stirring and the
mixture stirred for 8 h. The mixture was extracted with ethyl
acetate (3 × 20 ml). The combined organic extracts were
washed with dilute HCl (2 M, 10 ml), brine (2 × 20 ml), dried
(MgSO4) and evaporated under reduced pressure. The product
was purified by flash column chromatography on silica gel (10%
EtOAc–light petroleum) to give complex 19 as a yellow crystal-
(ii) Preparation of (1S,1ЈS)-tricarbonyl{ꢀ6-[1-diphenyl-
phosphino-2-(1-hydroxy-1-phenylmethyl)]benzene}chromium(0)
21. The above typical protocol was followed using complex (Ϫ)-
20 (0.18 g). Flash column chromatography on silica gel (20%
EtOAc–light petroleum) gave complex 21 as a yellow solid (109
mg, 83%), mp 167 ЊC; [α]D22 Ϫ206 (c 1.0 in CHCl3) (Found: C,
66.49; H, 4.22. C28H21O4PCr requires C, 66.66; H, 4.20%); νmax
(CHCl3)/cmϪ1 1972 and 1904 (C᎐O); δ (400 MHz, CDCl ) 2.32
᎐
᎐
H
3
line solid (79 mg, 81%), mp 164 ЊC; νmax (CHCl3)/cmϪ1 1963 and
(1H, d, J 3, D2O exch., CHOH), 4.86 (1H, d, J 6, CrCH), 5.13
(1H, dd, J 6 and 6, CrCH), 5.69 (1H, dd, J 6 and 6, CrCH),
5.89 (1H, dd, J 6 and J 3, CrCH), 6.57 (1H, dd, J 7 and J 3,
CHOH), 6.86–6.97 (5H, m, ArH), 7.04 (2H, m, ArH), 7.15
(3H, m, ArH) and 7.33–7.39 (5H, m, ArH); δC (68 MHz,
CDCl3) 71.7 (d, J 26, CHOH), 86.7 (d, J 5, CrCH), 90.0
(CrCH), 94.9 (CrCH), 98.2 (d, J 2, CrCH), 100.8 (d, JP-C 26,
CrC), 121.5 (d, JP-C 21, CrC), {(127.9, 128.0, 128.1, 128.2,
128.4, 128.6, 128.7), (ArCH)2P}, {(129.7, 132.6, 132.9),
ArCH}, 133.9 [d, JP-C 12, (ArC)2P], 134.4 [d, JP-C 7, (ArC)2P],
{(134.6, 134.9), ArCH}, 140.2 (ArC) and 232.1 (3CO); m/z
(EI) 504.5 [Mϩ, 6%], 448.5 [(M Ϫ 2CO)ϩ, 1%] and 420.4
[(M Ϫ 3CO)ϩ, 100%] (HRMS: found Mϩ, 504.05646. Requires
M, 504.05826).
᎐
1900 (C᎐O); δH (400 MHz, CDCl3) 0.04 [9H, s, Si(CH3)3], 0.23
᎐
[9H, s, Si(CH3)3], 4.77 (1H, d, J 1, CrCH), 5.16 (1H, m, CrCH),
5.35 (1H, m, CrCH), 7.17 [3H, m, (ArH)2P] and 7.28 [7H, m,
(ArH)2P]; δC (100 MHz, CDCl3) Ϫ1.5 [Si(CH3)3], 1.3 [Si(CH3)3],
97.0 (d, JP-C 12, CrCH), 98.8 (CrCH), 99.6 (CrC), 102.6
(CrCH), 107.9 (d, JP-C 22, CrC), 109.5 (d, JP-C 41, CrC),
{(128.5, 128.6, 128.7, 128.9, 129.6, 133.3, 133.5, 134.5, 134.7),
ArCH}, 135.3 (d, JP-C 14, ArC), 137.6 (d, JP-C 11, ArC) and
232.6 (3CO); m/z (FAB) 542 (Mϩ, 24%), 458 [(M Ϫ 3CO)ϩ,
100%] and 406 [(M Ϫ 3CO Ϫ Cr)ϩ, 14%] (HRMS: found Mϩ,
542.0950. Requires M, 542.0954).
(iii) Preparation of (2R)-tricarbonyl[ꢀ6-(1-diphenylphosphino-
2-tributylstannyl)benzene]chromium(0) 20. To a mixture of
complex (Ϫ)-16 (0.10 g, 0.14 mmol) and polymethylhydro-
siloxane (90 µl, 1.40 mmol of H equiv.) in THF (5 ml) was
added Ti(OiPr)4 (42 µl, 0.14 mmol) and the mixture heated at
reflux overnight. The reaction mixture was cooled to room
temperature and diluted with THF (20 ml). NaOH solution
(2 M, 100 ml) was added slowly with vigorous stirring and the
mixture stirred for 8 h. The mixture was extracted with ethyl
acetate (3 × 20 ml). The combined organic extracts were
washed with dilute HCl (2 M, 10 ml), brine (2 × 20 ml), dried
(MgSO4) and evaporated under reduced pressure. The product
was purified by flash column chromatography on silica gel (10%
EtOAc–light petroleum), to give complex 20 as a yellow crystal-
line solid (89 mg, 93%), mp 78 ЊC; [α]D22 Ϫ161 (c 0.85 in CHCl3);
The enantiomeric excess of 21 was determined to be 81%
using a Chiralcel OD column with 90:10 hexane–IPA as eluent.
Flow rate 1 ml minϪ1. Detection 256 nm. Retention times 12.7
min (major) and 24.0 min (minor).
(iii) Preparation of (2S)-tricarbonyl{ꢀ6-[1-diphenylphosphino-
2-(1-cyclohexyl-1-hydroxymethyl)]benzene}chromium(0) 22. The
above typical protocol was followed using complex (Ϫ)-20
(0.20 g), to give the product as a 9:1 mixture of diastereomers,
as indicated by the 1H NMR spectrum. The resulting yellow resi-
due was purified by flash column chromatography on silica gel
(20% EtOAc–light petroleum) to give the major stereoisomer of
22 as a yellow solid (103 mg, 70%), mp 186 ЊC; [α]D22 Ϫ257 (c 0.45
in CHCl3) (Found: C, 65.56; H, 5.56. C28H27O4PCr requires C,
65.88; H, 5.33%); νmax (CHCl3)/cmϪ1 3615 (OH), 1966 and 1904
νmax (CHCl3)/cmϪ1 1964 and 1896 (C᎐O); δ (250 MHz, CDCl )
᎐
᎐
H
3
᎐
(C᎐O); δ (400 MHz, CDCl3) 0.34–1.36 (11H, m, Cyhx), 1.74
᎐
H
0.85 (9H, t, J 7, Sn[(CH2)3CH3]3), 1.05 (6H, m, Sn[(CH2)3-
CH3]3), 1.15–1.30 (6H, m, Sn[(CH2)3CH3]3), 1.36–1.46 (6H,
m, Sn[(CH2)3CH3]3), 4.79–4.82 (1H, m, CrCH), 5.23–5.28 (2H,
m, CrCH), 5.34–5.37 (1H, m, CrCH) and 7.24–7.36 [10H, m,
(ArH)2P]; δC (68 MHz, CDCl3) 12.3 (3CH2), 13.6 (3CH2), 27.3
(3CH2), 28.9 (3CH3), 92.2 (CrCH), 94.2 (CrCH), 97.1 (CrCH),
100.0 (d, JP-C 17, CrCH), 110.2 (d, JP-C 61, CrC), 118.1 (d, JP-C
10, CrC), {(128.4, 128.5, 128.5, 128.6, 129.0, 129.6, 133.2,
133.5, 134.3, 134.6), ArCH}, 137.0 (d, JP-C 10, ArC) and 232.7
(3CO); m/z (EI) 687 (Mϩ, 1%), 631 [(M Ϫ 2CO)ϩ, 23%] and
603 [(M Ϫ 3CO)ϩ, 2%].
(1H, d, J 4, D2O exch., CHOH), 4.90 (1H, d, J 6, CrCH), 5.12
(1H, dd, J 6 and 6, CrCH), 5.34–5.41 (1H, m, CrCH), 5.50–
5.53 (1H, m, CHOH), 5.60 (1H, dd, J 6, CrCH) and 7.38–7.42
[10H, m, (ArH)2P]; δC (68 MHz, CDCl3) 23.6 (CH2), 25.8
(CH2), 26.0 (CH2), 26.4 (CH2), 30.4 (CH2), 43.4 (CH2), 72.8 (d,
J 26, CH), 87.8 (d, J 5, CrCH), 90.0 (CrCH), 94.7 (CrCH), 98.3
(d, J 2, CrCH), 101.4 (d, J 24, CrC), 122.2 (d, J 21, CrC),
{(128.6, 128.7, 128.9, 129.5, 129.6, 133.5, 133.8, 134.5, 134.8),
(ArCH)2P}, 133.5 (d, JP-C 12, ArC), 135.8 (d, JP-C 9, ArC) and
232.3 (3CO); m/z (EI) 510 [Mϩ, 2.3%], 426 [(M Ϫ 3CO)ϩ, 100%]
(HRMS: found Mϩ, 510.10719. Requires M, 510.10519). The
minor diastereomer was not characterised.
Typical procedure for transmetallation–electrophilic quench to
give chiral phosphine complexes in Table 1
(i) Preparation of (2S)-tricarbonyl[ꢀ6-(1-diphenylphosphino-2-
trimethylsilyl)benzene]chromium(0) 18. n-BuLi (0.18 ml of a
1.55 M solution in hexane, 0.28 mmol) was added dropwise to a
solution of complex (Ϫ)-20 (98 mg, 0.14 mmol) in THF (10 ml)
(iv) Preparation of (2S)-tricarbonyl[ꢀ6-(1-diphenylphosphino-
2-benzoyl)benzene]chromium(0) 23. The above typical protocol
was followed using complex (Ϫ)-20 (0.28 g). Flash column
chromatography on silica gel (20% EtOAc–light petroleum)
gave complex 23 as a red solid (144 mg, 70%), mp 157 ЊC; [α]D22
3184
J. Chem. Soc., Perkin Trans. 1, 1999, 3177–3189

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Ϫ66 (c 1.1 in CHCl3) (Found: C, 66.82; H, 4.31. C28H19O4PCr
(viii) Preparation of (2R)-tricarbonyl[ꢀ6-(1-diphenylphos-
requires C, 66.93; H, 3.81%); νmax (CHCl3)/cmϪ1 1982, 1919
phino-2-bromo)benzene]chromium(0) 27. The above typical
protocol was followed using complex (Ϫ)-20 (0.38 g). Flash
column chromatography on silica gel (10% EtOAc–light petrol-
eum) gave complex 27 as a yellow solid (161 mg, 61%), mp
169 ЊC; [α]D22 Ϫ270 (c 0.52 in CHCl3) (Found: C, 52.59; H, 2.79;
Br, 16.63. C21H14BrO3PCr requires C, 52.85; H, 2.96; Br,
᎐
(C᎐O) and 1694 (C᎐O); δH (400 MHz, CDCl3) 4.90 (1H, d, J 6,
᎐
᎐
CrCH), 5.30 (1H, ddd, J 6 and 1, CrCH), 5.43 (1H, dd, J 6,
CrCH), 5.50 (1H, ddd, J 7, 2 and 1, CrCH), 7.25–7.46 [13H,
m, ((ArH)2P ϩ ArH)] and 7.73 (2H, m, ArH); δC (68 MHz,
CDCl3) 90.8 (CrCH), 91.5 (CrCH), 94.7 (d, JP-C 4, CrCH), 96.0
(d, JP-C 2, CrCH), 103.8 (d, JP-C 32, CrC), 110.2 (d, JP-C 21,
CrC), {(128.2, 128.4, 128.5, 128.6, 128.7, 128.9, 129.5),
(ArCH)2P}, {(132.9, 133.1, 133.5, 134.5, 134.9), ArCH}, 135.0
16.58%); νmax (CHCl3)/cmϪ1 1980 and 1915 (C᎐O); δ (400
᎐
᎐
H
MHz, CDCl3) 4.75 (1H, dd, J 6 and 1, CrCH), 4.92 (1H, ddd,
J 6, 6 and 1, CrCH), 5.43 (1H, dd, J 6 and 1, CrCH), 5.55 (1H,
m, CrCH) and 7.41 (10H, m, ArH); δC (100 MHz, CDCl3) 88.1
(CrCH), 94.1 (CrCH), 94.1 (CrCH), 96.2 (CrCH), 103.4 (d,
JP-C 20, CrC), 107.2 (d, JP-C 31, CrC), {(128.9, 128.9, 129.0
129.0, 129.4, 130.1, 133.2, 133.4, 134.8, 135.0), (ArCH)2P},
134.0 (d, JP-C 15, ArC), 135.3 (d, JP-C 11, ArC) and 231.3 (3CO);
m/z (FAB) 479, 477 [(M ϩ H)ϩ, 10%]; 422, 420 [(M Ϫ 2CO)ϩ,
14%]; 394, 392 [(M Ϫ 3CO)ϩ, 19%].
(d, JP-C 17, ArC), 136.3 (ArC), 193.8 (C᎐O) and 230.7 (3CO);
᎐
m/z (EI) 502.0 (Mϩ, 8%), 418.0 [(M Ϫ 3CO)ϩ, 90%)] (HRMS:
found Mϩ, 502.0404. Requires M, 502.0426).
(v) Preparation of (2S)-tricarbonyl[ꢀ6-(1-diphenylphosphino-
2-methyl)benzene]chromium(0) 24. The above typical protocol
was followed using complex (Ϫ)-20 (0.25 g). Flash column
chromatography on silica gel (20% EtOAc–light petroleum)
gave complex 24 as a yellow solid (100 mg, 67%), mp 172 ЊC;
[α]D22 Ϫ282 (c 0.93 in CHCl3) (Found: C, 64.07; H, 4.18.
Suzuki couplings according to Scheme 8
(i) Preparation of (2S)-tricarbonyl[ꢀ6-(1-diphenylphosphino-2-
phenyl)benzene]chromium(0) 28. A mixture of complex (Ϫ)-
20 (100 mg, 0.21 mmol), benzeneboronic acid (51 mg, 0.42
mmol), sodium carbonate (44 mg, 0.42 mmol) and Pd(PPh3)4
(24 mg, 0.02 mmol) in methanol (4 ml) and water (0.4 ml) was
degassed by three cycles of freeze–pump–thaw and stirred at
75 ЊC for 12 h under nitrogen. The reaction mixture was
quenched with water and extracted with ethyl acetate (2 × 5
ml). The combined organic extracts were washed with aqueous
NaOH (2 × 10 ml of 2 M solution), brine (20 ml), dried over
MgSO4 and the solvent was evaporated under reduced pres-
sure. The yellow residue was purified by flash column chrom-
atography on silica gel (10% EtOAc–light petroleum) to give
complex 28 as a yellow solid (83 mg, 83%), mp 61 ЊC; [α]D20 Ϫ149
C22H17O3PCr requires C, 64.07; H, 4.16%); νmax (CHCl3)/cmϪ1
᎐
1968 and 1898 (C᎐O); δH (400 MHz, CDCl3) 2.27 (3H, s, CH3),
᎐
4.76 (1H, d, J 6, CrCH), 4.99 (1H, dd, J 6 and 6, CrCH), 5.10
(1H, dd, J 6 and 6, CrCH), 5.47 (1H, dd, J 6 and 6, CrCH) and
7.31–7.38 [10H, m, (ArH)2P]; δC (68 MHz, CDCl3) 20.0 [d, J 21,
CH3], 88.8 (CrCH), 92.2 (d, J 4, CrCH), 94.9 (CrCH), 97.3
(CrCH), 102.7 (d, J 20, CrC), 114.5 (d, J 23, CrC), {(128.7,
128.8, 128.8, 128.9, 129.3, 129.7, 133.1, 133.5, 134.5, 134.8),
(ArCH)2P}, 133.3 (ArC), 135.3 (d, JP-C 11, ArC) and 232.6
(3CO); m/z (EI) 412.7 (Mϩ, 15%), 356.6 [(M Ϫ 2CO)ϩ, 1%)]
and 328.6 [(M Ϫ 3CO)ϩ, 100%] (HRMS: found Mϩ, 412.0322.
C22H17O3PCr requires M, 412.0320).
(vi) Preparation of (2S)-tricarbonyl[ꢀ6-(1-diphenylphosphino-
2-ethyl)benzene]chromium(0) 25. The above typical protocol was
followed using complex (Ϫ)-20 (0.17 g). Flash column chrom-
atography on silica gel (20% EtOAc–light petroleum) gave
complex 25 as a yellow oil (56 mg, 53%), [α]D25 Ϫ267 (c 1 in
(c 0.42 in CHCl3); νmax (CHCl3/cmϪ1) 1970 and 1903 (C᎐O);
᎐
᎐
δH (400 MHz, CDCl3) 4.84 (1H, d, J 6, CrCH), 5.27 (1H, dd, J 6
and 6, CrCH), 5.35 (1H, m, CrCH), 5.45 (1H, dd, J 6 and 6,
CrCH) and 7.17–7.38 [15H, m, (ArH)2P ϩ Ph]; δC (100 MHz,
CDCl3) 91.7 (CrCH), 91.8 (CrCH), 95.5 (CrCH), 105.2 (d, J P-C
23, CrC), 119.9 (d, J P-C 25, CrC), {(127.8, 128.6, 128.7, 129.2,
129.5, 130.7, 133.7, 133.9, 134.7, 134.9), ArCH}, 134.4 (d, J 15,
ArC), 136.2 (ArC), 136.3 (d, J 10, ArC) and 232.3 (3CO);
m/z (FAB) 475 [(M ϩ H)ϩ, 18%], 390 [(M Ϫ 3CO)ϩ, 100%]
(HRMS: found Mϩ, 475.0548. C27H19O3PCr ϩ H requires M,
475.0535).
CHCl3); νmax (CHCl3)/cmϪ1 1952, 1916 and 1864 (C᎐O); δ (400
᎐
᎐
H
MHz, CDCl3) 0.97 (3H, dd, J 7 and 7, CH3), 2.74 (1H, dq, JAB
15 and J 7, CHH), 2.90 (1H, ddq, JAB 15, J 7 and 4, CHH), 4.81
(1H, d, J 6, CrCH), 5.04 (1H, ddd, J 6 and 1, CrCH), 5.16 (1H,
dd, J 6 and 3, CrCH), 5.53 (1H, dd, J 6, CrCH) and 7.41 [10H,
m, (ArH)2P]; δC (100 MHz, CDCl3) 14.2 (CH3), 26.2 (d, JP-C 23,
CH2), 89.2 (CrCH), 89.9 (CrCH), 95.1 (CrCH), 97.8 (CrCH),
102.8 (d, JP-C 20, CrC), 120.5 (d, JP-C 22, CrC), 128.8 (ArCH),
{(129.4, 129.7, 133.6, 133.8), ArCH}, 134.0 (d, JP-C 14, ArC),
{(134.6, 134.8), ArCH}, 135.9 (d, JP-C 10, ArC) and 232.6
(3CO); m/z (EI) 426 (Mϩ, 5%), 342 [(M Ϫ 3CO)ϩ, 100%];
(HRMS: found Mϩ, 426.0482. C23H19O3PCr requires M,
426.0477).
(ii) Preparation of (2S)-tricarbonyl{ꢀ6-[1-diphenylphosphino-
2-(p-methoxyphenyl)]benzene}chromium(0) 29. A mixture of
complex (Ϫ)-20 (100 mg, 0.21 mmol), 4-methoxybenzene-
boronic acid (64 mg, 0.42 mmol), sodium carbonate (44 mg,
0.42 mmol) and Pd(PPh3)4 (24 mg, 0.02 mmol) in methanol (4
ml) and water (0.4 ml) was degassed by three cycles of freeze–
pump–thaw and stirred at 75 ЊC for 0.5 h under nitrogen. The
reaction mixture was quenched with water and extracted with
ethyl acetate (2 × 5 ml). The combined organic extracts were
washed with aqueous NaOH (2 × 10 ml of 2 M solution), brine
(20 ml) and dried over MgSO4 and the solvent was evaporated
under reduced pressure. The yellow residue was purified by
flash column chromatography on silica gel (10% EtOAc–light
petroleum) to give complex 29 as a yellow solid (91 mg, 86%),
(vii) Preparation of (2S)-tricarbonyl[ꢀ6-(1-diphenylphosphino-
2-benzyl)benzene]chromium(0) 26. The above typical protocol
was followed using complex (Ϫ)-20 (0.27 g). Flash column
chromatography on silica gel (20% EtOAc–light petroleum)
gave complex 26 as a yellow solid (57 mg, 31%), mp 164 ЊC; [α]D25
Ϫ149 (c 0.75 in CHCl3) (Found: C, 68.60; H, 4.27. C28H21O3PCr
requires C, 68.84; H, 4.34%); νmax (CHCl3)/cmϪ1 1966 and 1904
᎐
(C᎐O); δ (250 MHz, CDCl ) 4.10 (2H, s, PhCH ), 4.80 (1H, d,
᎐
H
3
2
J 6, CrCH), 4.89 (1H, dd, J 6 and 3, CrCH), 5.05 (1H, dd, J 6,
CrCH), 5.43 (1H, dd, J 6, CrCH), 7.04–7.14 (5H, m, ArH) and
7.24–7.39 [10H, m, (ArH)2P]; δC (68 MHz, CDCl3) 39.0 (d, JP-C
22, PhCH2), 90.2 (CrCH), 92.3 (CrCH), 94.9 (CrCH), 98.0
(CrCH), 103.2 (d, JP-C 21, CrC), 118.5 (d, JP-C 22, CrC),
{(127.2, 128.9, 129.0, 129.1, 129.2, 129.6, 129.9, 130.1, 133.7,
134.0), ArCH}, 134.4 (d, JP-C 10, ArC), {(134.9, 135.2),
ArCH}, 137.5 (ArC) and 232.9 (3CO); m/z (EI) 488 (Mϩ, 8%),
404 [(M Ϫ 3CO)ϩ, 100%] (HRMS: found Mϩ, 488.0627.
C28H21O3PCr requires M, 488.0633).
mp 68 ЊC; [α]D25 Ϫ91 (c 0.47 in CHCl3); νmax (CHCl3)/cmϪ1 1970
᎐
and 1903 (C᎐O); δ (400 MHz, CDCl ) 3.79 (3H, s, OCH ), 4.87
᎐
H
3
3
(1H, d, J 6, CrCH), 5.25 (1H, dd, J 6 and 6, CrCH), 5.34 (1H,
m, CrCH), 5.47 (1H, dd, J 6 and 6, CrCH), 6.73 (2H, d, J 8,
p-ArH), 7.17 (2H, d, J 8, p-ArH) and 7.37 [10H, m, (ArH)2P];
δC (100 MHz, CDCl3) 55.3 (OCH3), 91.5 (CrCH), 92.3 (CrCH),
95.5 (CrCH), 96.0 (CrCH), 105.4 (d, JP-C 23, CrC), 113.2
(CrCH), 120.0 (d, JP-C 25, CrC), {(120.1, 128.6, 128.7, 128.8,
129.2, 129.6, 132.0, 133.7, 133.9), ArCH}, 134.6 (ArC),
{(134.8, 135.0), ArCH}, 136.6 (d, JP-C 10, ArC), 159.9 (ArC)
J. Chem. Soc., Perkin Trans. 1, 1999, 3177–3189
3185

View Article Online
and 232.5 (3CO); m/z (FAB) 505 [(M ϩ H)ϩ, 5%], 420
[(M Ϫ 3CO)ϩ, 16%] (HRMS: found (M ϩ H)ϩ, 505.0689.
C28H21O4PCr ϩ H requires (M ϩ H), 505.0661).
ml) was added and the mixture was allowed to warm to room
temperature. The organic layer was separated, washed with
saturated aqueous NaHCO3 (10 ml), HCl solution (2 M, 30 ml),
brine (30 ml), dried (MgSO4). The solvent was evaporated
under reduced pressure and the resulting yellow oil was then
purified by flash column chromatography on silica gel (5%
EtOAc–light petroleum) to give firstly an unwanted doubly
silylated by-product (tricarbonyl[η6-2,6-bis(trimethylsilyl)-
anisole]chromium(0) as a yellow solid (51 mg, 6%), mp 98–
(iii) Preparation of (2S)-tricarbonyl{ꢀ6-[1-diphenylphos-
phino-2-(2-thienyl)]benzene}chromium(0) 30.
A mixture of
complex (Ϫ)-20 (100 mg, 0.21 mmol), 2-thiopheneboronic acid
(54 mg, 0.42 mmol), sodium carbonate (44 mg, 0.42 mmol) and
Pd(PPh3)4 (24 mg, 0.02 mmol) in methanol (4 ml) and water
(0.4 ml) was degassed by three cycles of freeze–pump–thaw and
stirred at 75 ЊC for 24 h under nitrogen. Reaction mixture was
quenched with water and extracted with ethyl acetate (2 × 5 ml).
The combined organic extracts were washed with aqueous
NaOH (2 × 10 ml of 2 M solution), brine (20 ml), dried over
MgSO4 and the solvent was evaporated under reduced pressure.
The yellow residue was purified by flash column chromato-
graphy (10% EtOAc–light petroleum) to give complex 30 a yel-
low oil (67 mg, 67%), [α]D22 Ϫ79 (c 0.25 in CHCl3); νmax (CHCl3)/
99 ЊC (lit.,5 84–85 ЊC); νmax (CHCl3)/cmϪ1 1961, 1908 and 1872
᎐
(C᎐O); δ (400 MHz, CDCl3) 0.40 [18H, s, 2Si(CH3)3], 3.73
᎐
H
(3H, s, OCH3), 4.82 (1H, t, J 6, CrCH) and 5.64 (2H, d, J 6,
CrCH); δC (68 MHz, CDCl3) 0.5 [2Si(CH3)3], 63.6 (OCH3), 87.6
(CrCH), 92.2 (2CrC), 101.9 (2CrCH), 153.0 (CrC) and 233.6
(3CO); m/z (EI) 388 (Mϩ, 5%), 304 [(M Ϫ 3CO)ϩ, 41%], 252
[(M Ϫ Cr(CO)3)ϩ, 20%] followed by the desired complex (ϩ)-3
as a yellow solid (540 mg, 84%), mp 110–111 ЊC (of a 99% ee
sample) (lit.,10 78–79 ЊC); [α]D23 195 (c 0.21 in CHCl3); νmax
(CHCl3)/cmϪ1 2958, 1965 and 1893; δH (400 MHz, CDCl3) 0.32
(9H, s, Si(CH3)3), 3.74 (3H, s, OCH3), 4.80 (1H, dd, J 6, CrCH),
4.99 (1H, d, J 6, CrCH), 5.59 (1H, dd, J 6 and J 1, CrCH) and
5.69 (1H, dd, J 6, CrCH); δC (100 MHz, CDCl3) Ϫ0.5
[Si(CH3)3], 55.4 (OCH3), 73.5 (CrCH), 85.1 (CrCH), 88.9
(CrC), 95.9 (CrCH), 101.8 (CrCH), 147.5 (CrC) and 233.7
(3CO); m/z (FAB) 316 (Mϩ, 62%), 260 [(M Ϫ 2CO)ϩ, 100%],
232 [(M Ϫ 3CO)ϩ, 68%] (HRMS: found Mϩ, 316.0237.
C13H16O4SiPCr requires M, 316.0223).
cmϪ1 1973 and 1906 (C᎐O); δH (400 MHz, CDCl3) 4.81 (1H, d,
᎐
᎐
J 6, CrCH), 5.22 (1H, ddd, J 6, 6 and 1, CrCH), 5.47 (1H, ddd,
J 6, 6 and 1, CrCH), 5.52 (1H, m, CrCH), 6.86 (1H, dd, J 5 and
4, CH-thiophene), 6.93 (1H, m, CH-thiophene), 7.23 (1H, dd,
J 5 and 1, CH-thiophene), 7.39 (9H, m, ArH) and 7.58 (1H, m,
ArH); δC (100 MHz, CDCl3) 91.5 (CrCH), 91.8 (CrCH), 95.7
(CrCH), 95.8 (CrCH), 105.8 (d, JP-C 23, CrC), 110.4 (d, JP-C
15, CrC), {(126.8, 127.1, 130.3), CH-thiophene}, {(128.2,
128.7, 128.8, 128.9, 129.3, 129.7, 133.0, 133.6, 133.8, 134.8,
135.0), (ArCH)2P}, 134.4 (d, J 15, ArC), 136.6 (d, J 10, ArC),
138.2 (ArC) and 232.1 (3CO); m/z (FAB) 481 [(M ϩ H)ϩ, 3%]
(HRMS: found [M ϩ H]ϩ, 481.0134. C25H17O3PSCr requires
[M ϩ H], 481.0120).
The enantiomeric excess of this sample was shown to be 79%
by use of a Chiralcel OJ column using 90:10 hexane–IPA as
eluent. Flow rate 1 ml minϪ1. Detection 256 nm. Retention
times 7.4 min (minor) and 10.2 min (major).
(iii) Phosphenylation of 3 via ortho-metallation and reaction
with Ph2PCl. n-BuLi (0.24 ml of a 1.55 M solution in hexanes,
0.37 mmol) was added dropwise to a solution of complex (ϩ)-3
(0.10 g, 0.32 mmol) in THF (10 ml) at Ϫ78 ЊC under an atmos-
phere of nitrogen. The mixture was stirred at Ϫ78 ЊC for 1 h
before addition of chlorodiphenylphosphine (0.17 ml, 0.95
mmol) dropwise, and reaction mixture was then stirred at
Ϫ78 ЊC for a further 1 h and then warmed to room temperature.
Saturated aqueous NaHCO3 (5 ml) was added in one portion.
The organic layer was separated, washed with brine (20 ml),
and dried (MgSO4). The solvent was evaporated under reduced
pressure, and the yellow residue was purified by flash column
chromatography on silica gel (5% EtOAc–light petroleum) to
give the desired phosphenylated complex as a yellow solid (0.12
g, 78%), mp 137 ЊC; [α]D23 234 (c 0.21 in CHCl3) (Found: C, 60.22;
H, 5.08. C25H25O4PSiCr requires C, 59.99; H, 5.03%); νmax
Chemical correlation as in Scheme 9
(i) Preparation of (2R)-tricarbonyl[ꢀ6-2-diphenylphosphino-
anisole]chromium(0) 31 via nucleophilic substitution reaction. To
a mixture of complex (Ϫ)-27 (73 mg, 0.15 mmol) and sodium
methoxide (41 mg, 0.77 mmol) in THF (5 ml) was added three
drops of 15-crown-5. The mixture was refluxed for 12 h, cooled
to room temperature and then water (3 ml) was added care-
fully. After addition of EtOAc (5 ml), the organic layer was
separated, washed with water (5 ml), brine (20 ml) and dried
(MgSO4). The solvent was evaporated under reduced pressure
and the resulting yellow residue was purified by flash column
chromatography on silica gel (10% EtOAc–light petroleum) to
give (Ϫ)-31 as a yellow solid (40 mg, 61%), mp 109 ЊC; [α]D24
Ϫ125 (c 0.81%, CHCl3); νmax (CHCl3)/cmϪ1 1969 and 1898
᎐
(C᎐O); δ (400 MHz, CDCl ) 3.69 (3H, s, OCH ), 4.74 (1H, dd,
᎐
H
3
3
(CHCl3)/cmϪ1 1972 and 1904 (C᎐O); δ (400 MHz, CDCl ) 0.37
J 6 and 6, CrCH), 4.86 (1H, d, J 6, CrCH), 5.02 (1H, dd, J 6
and JP-H 3, CrCH), 5.59 (1H, dd, J 6 and 6, CrCH) and 7.32–
7.40 (10H, m, ArH); δC (100 MHz, CDCl3) 56.2 (OCH3), 72.9
(CrCH), 85.2 (CrCH), 93.4 (d, JP-C 23, CrC), 94.5 (CrCH),
98.3 (CrCH), {(128.6, 128.7, 128.8, 128.9, 129.1, 129.7, 133.0,
133.2), ArCH}, 134.1 (d, JP-C 4, ArC), {(134.8, 135.0), ArCH},
136.1 (d, JP-C 3, ArC), 145.9 (d, JP-C 3, CrC) and 232.5 (3CO);
m/z (EI) 428 (Mϩ, 0.14%), 372 [(M Ϫ 2CO)ϩ, 8%], 344
[(M Ϫ 3CO)ϩ, 38%], 292 [(M Ϫ Cr(CO)3)ϩ, 100%] (HRMS:
found Mϩ, 428.0270. C22H17O4PCr requires M, 428.0270).
᎐
᎐
H
3
(9H, s, Si(CH3)3), 3.64 (3H, s, OCH3), 4.76 (1H, dd, J 6, CrCH),
5.12 (1H, d, J 6, CrCH), 5.57 (1H, d, J 6, CrCH) and 7.41–7.48
[10H, m, (ArH)2P]; δC (100 MHz, CDCl3) 0.2 [Si(CH3)3], 64.7
(OCH3), 87.0 (CrCH), 92.1 (CrC), 96.4 (d, JP-C 26, CrC), 99.2
(CrCH), 100.4 (CrCH), {(128.8, 128.8, 129.1, 129.8, 133.2,
133.4, 135.1, 135.29), ArCH}, 134.7 (d, JP-C 13, ArC), 137.4 (d,
JP-C 12, ArC), 151.2 (d, JP-C 18, CrC) and 232.4 (3CO); m/z (EI)
500 (Mϩ, 3%), 416 [(M Ϫ 3CO)ϩ, 100%] (HRMS: found Mϩ,
500.0668. Requires M, 500.0665).
(ii) Preparation of (2R)-tricarbonyl(ꢀ6-2-trimethylsilyl-
anisole)chromium(0) 3.10 A solution of the chiral base 2
(ϩLiCl) was prepared, as described above, by addition of n-BuLi
(2.89 ml of a 1.55 M solution in hexanes, 4.48 mmol) to a
solution of the corresponding chiral amine hydrochloride salt
(0.59 g, 2.25 mmol) in THF (20 ml). The resulting solution of
chiral base 2 (ϩLiCl) was then cooled to Ϫ100 ЊC and chloro-
trimethylsilane (1.30 ml, 10.24 mmol) was added in one portion
followed by a solution of anisole complex 1 (0.50 g, 2.04 mmol)
in THF (2 ml). The reaction mixture was allowed to warm to
Ϫ78 ЊC and stirred for 0.50 h. Saturated aqueous NaHCO3 (10
(iv) Preparation of (2S)-tricarbonyl(ꢀ6-2-diphenylphosphino-
anisole)chromium(0) (؊)-31 by a desilylation reaction. To a
stirred solution of the complex from (iii) above (87 mg, 0.17
mmol) in THF (10 ml) at Ϫ78 ЊC under an atmosphere of
nitrogen, was added TBAF (0.17 ml of a 1.0 M solution in
THF, 0.17 mmol) dropwise. After stirring the mixture at
Ϫ78 ЊC for 0.5 h, saturated aqueous NH4Cl (2.5 ml) was added
and the reaction mixture was then warmed to room temper-
ature. The mixture was extracted with CH2Cl2 (10 ml), the
organic extract was washed with water (10 ml), brine (10 ml),
dried (MgSO4) and the solvent evaporated under reduced pres-
3186
J. Chem. Soc., Perkin Trans. 1, 1999, 3177–3189

View Article Online
sure. The resulting yellow oil was purified by flash column
chromatography on silica gel (10% EtOAc–light petroleum) to
give (ϩ)-31 as a yellow solid (71 mg, 95%), [α]D23 122 (c 1.1 in
CHCl3). The 1H NMR spectrum of the product was identical to
that described above for (Ϫ)-31.
116.6 (CrC) and 232.8 (3CO); m/z (EI) 286 (Mϩ, 24%), 202
[(M Ϫ 3CO)ϩ, 100%] (HRMS: found Mϩ, 285.9764. Requires
M, 285.9756).
The enantiomeric excess of complex 33 was determined to be
94% using a Chiralcel OD column using 95:5, hexane–IPA as
eluent. Flow rate 1 ml minϪ1. Detection 256 nm. Retention time
18.7 min (major) and 23.7 (minor).
Asymmetric substitution of complex 6 according to Table 2
Enantiomerically pure material {[α]D23 Ϫ117 (c 0.50 in CHCl3),
(i) Preparation of (1R,3ЈS)-tricarbonyl[ꢀ6-1-trimethylsilyl-
1,3-dihydroisobenzothiophene]chromium(0) 32 (Me3SiCl in situ
quench). A solution of the bis-lithium amide base 9 was pre-
pared by addition of n-BuLi (0.55 ml of a 1.6 M solution in
hexanes, 0.89 mmol) to a solution of the appropriate chiral
diamine (186 mg, 0.44 mmol) in THF (10 ml) at Ϫ78 ЊC under
an atmosphere of nitrogen. The solution was allowed to warm
to room temperature with stirring and then recooled to
Ϫ100 ЊC. Chlorotrimethylsilane (0.23 ml, 1.81 mmol) was
added in one portion, followed by a solution of complex 6 (100
mg, 0.37 mmol) in THF (2 ml). The reaction mixture was
stirred at this temperature for 1 h before MeOH (1 ml) was
added with subsequent warming to room temperature. The
solvents were removed under reduced pressure and the resulting
yellow residue was purified by flash column chromatography on
silica gel (10% EtOAc–light petroleum) to give complex 32 as
a yellow solid (121 mg, 95%), mp 110 ЊC; [α]D23 Ϫ7 (c 0.62 in
CHCl3) (Found: C, 48.77; H, 4.62; S, 9.25. C14H16O3SCrSi
i
ee ≥99%} could be obtained by recrystallisation from PrOH
(89% recovery).
Preparation of (1S,3ЈS)-tricarbonyl(η6-1-ethyl-1,3-dihydro-
isobenzothiophene)chromium(0) 34. The above typical protocol
was followed, using 0.30 g of 6. Flash column chromatography
on silica gel (15–25% EtOAc–light petroleum) gave complex 34
as a yellow solid (300 mg, 91%), mp 98 ЊC; [α]D23 Ϫ146 (c 0.3
in CHCl3); νmax (CHCl3)/cmϪ1 1971 and 1901 (C᎐O); δ (250
᎐
᎐
H
MHz, CDCl3) 1.03 (3H, t, J 7, CH3), 1.58–1.98 (2H, m, CH2),
3.80 (1H, d, JAB 14, SCHH), 4.19 (2H, m, SCHH ϩ SCH), 5.26
(2H, m, CrCH) and 5.45 (2H, m, CrCH); δC (68 MHz, CDCl3)
12.2 (CH3), 33.5 (CH2), 36.5 (CH2), 55.5 (CH), 90.4 (CrCH),
90.7 (CrCH), 91.7 (CrCH), 92.2 (CrCH), 111.9 (CrC), 115.6
(CrC) and 233.0 (3CO); m/z (FAB) 300 (Mϩ, 68%), 244
[(M Ϫ 2CO)ϩ, 65%], 216 [(M Ϫ 3CO)ϩ, 30%] (HRMS: found
Mϩ, 299.9929. Requires M, 299.9912).
The enantiomeric excess of complex 34 was determined to be
87% using a Chiralcel OD column with 95:5, hexane–IPA as
eluent. Flow rate 1 ml minϪ1. Detection 256 nm. Retention time
15.6 min (major) and 20.1 (minor).
requires C, 48.82; H, 4.68; S, 9.31%); νmax (CHCl3)/cmϪ1 1968
᎐
and 1894 (C᎐O); δ (400 MHz, CDCl ) 0.13 (9H, s, SiMe ), 3.40
᎐
H
3
3
4
Preparation of (1S,3ЈS)-tricarbonyl(η6-1-benzyl-1,3-dihydro-
isobenzothiophene)chromium(0) 35. The above typical
protocol was followed, using 1.0 g of 6. Flash column chrom-
atography on silica gel (10–20% EtOAc–light petroleum) gave
complex 35 as a yellow solid (932 mg, 70%), mp 90 ЊC; [α]D23
(1H, d, JH-H 2, SCH), 3.81 (1H, d, JAB 14, SCHH), 4.05 (1H,
dd, JAB 14 and JH-H 2, SCHH), 5.18 (1H, m, CrCH), 5.29
4
(2H, m, CrCH) and 5.48 (1H, d, J 6, CrCH); δC (68 MHz,
CDCl3) Ϫ3.1 [Si(CH3)], 36.7 (CH2), 39.9 (CH), 88.0 (CrCH),
89.9 (CrCH), 90.8 (CrCH), 91.3 (CrCH), 109.3 (CrC), 117.0
(CrC) and 232.8 (3CO); m/z (EI) 344 (Mϩ, 16%), 260
[(M Ϫ 3CO)ϩ, 44%] (HRMS: found Mϩ, 343.9992. requires M,
343.9994).
The enantiomeric excess of complex 32 was determined to be
89% using a Chiralcel OD column with 97.5:2.5 hexane–IPA as
eluent. Flow rate 1 ml minϪ1. Detection 256 nm. Retention time
8.3 min (major) and 11.9 min (minor). Enantiomerically pure
material (ee ≥99%) could be obtained by recrystallisation from
iPrOH (85% recovery).
Ϫ177 (c 1.15 in CHCl3); νmax (CHCl3)/cmϪ1 1961 and 1876
᎐
(C᎐O); δ (400 MHz, CDCl3) 3.04–3.19 (2H, m, CH2), 3.63
᎐
H
(1H, d, JAB 14, SCHH), 3.81 (1H, d, JAB 14, SCHH), 4.43 (1H,
dd, J 7, 7, CH), 5.11–5.15 (2H, m, CrCH), 5.21–5.25 (1H, m,
CrCH), 5.36 (1H, d, J 6, CrCH) and 7.11–7.28 (5H, m, ArH);
δC (68 MHz, CDCl3) 35.5 (CH2), 45.4 (CH2), 53.6 (CH), 89.6
(CrCH), 90.0 (CrCH), 90.2 (CrCH), 91.4 (CrCH), 111.3 (CrC),
113.7 (CrC), 126.9 (ArCH), 128.3 (ArCH), 129.8 (ArCH),
137.0 (ArC) and 232.3 (3CO); m/z (EI) 362 (Mϩ, 4%), 278
[(M Ϫ 3CO)ϩ, 20%] and 135 [(C8H7S)ϩ, 100%] (HRMS: found
Mϩ, 362.0061. C15H14O3SCr requires M, 362.0069).
(ii) Preparation of complexes 33–38. Typical procedure:
(1S,3ЈS)-tricarbonyl(η6-1-methyl-1,3-dihydroisobenzothio-
phene)chromium(0) 33. A solution of the bis-lithium amide
base 9 was prepared by addition of n-BuLi (0.50 ml of a 1.6 M
solution in hexanes, 0.80 mmol) to a solution of the appropriate
chiral diamine (0.17 g, 0.40 mmol) in THF (10 ml) at Ϫ78 ЊC
under an atmosphere of nitrogen. The solution was allowed
to warm to room temperature with stirring and then cooled to
Ϫ100 ЊC. To the resulting pink solution was added a solution of
LiCl (7.7 mg, 0.18 mmol) in THF (5 ml) via a cannula, followed
by a solution of complex 6 (100 mg, 0.37 mmol) in THF (10 ml)
dropwise. The red solution was stirred at Ϫ100 ЊC for a further
1 h. Iodomethane (0.12 ml, 1.9 mmol) was added in one portion
and the reaction mixture was allowed to warm to Ϫ78 ЊC and
maintained at this temperature for a further 1 h. MeOH (1 ml)
was added with subsequent warming to room temperature
before the solvents were removed under reduced pressure. The
residue was purified by flash column chromatography on silica
gel (10–20% EtOAc–light petroleum) to give complex 33 as a
yellow solid (100 mg, 95%), mp 118 ЊC; [α]D23 Ϫ110 (c 0.53 in
CHCl3) (Found: C, 50.63; H, 3.53. C12H10O3SCr requires C,
Preparation of (1S,3ЈS)-tricarbonyl[η6-1-(1-diphenyl-1-
hydroxymethyl)-1,3-dihydroisobenzothiophene]chromium(0) 36.
The above typical protocol was followed, using 0.2 g of 6. Flash
column chromatography on silica gel (10–20% EtOAc–light
petroleum) gave complex 36 as a yellow solid (290 mg, 88%),
mp 158 ЊC; [α]D22 Ϫ118 (c 0.98 in CHCl3); νmax (CHCl3)/cmϪ1 3528
᎐
(OH), 1963 and 1879 (C᎐O); δ (400 MHz, CDCl ) 3.15 (1H, s,
᎐
H
3
D2O exch., OH), 3.74 (1H, d, JAB 14, SCHH), 4.09 (1H, d, JAB
14, SCHH), 4.18 (1H, s, SCH), 4.79 (1H, dd, J 6, 6, CrCH),
5.23 (1H, dd, J 6, 6, CrCH), 5.32 (1H, d, J 2, CrCH), 5.37 (1H,
d, J 6, CrCH), 7.26–7.37 (8H, m, ArH) and 7.48 (2H, d, J 8,
ArH); δC (126 MHz, CDCl3) 36.6 (CH2), 62.9 (CH), 82.0 (C),
89.0 (CrCH), 89.2 (CrCH), 92.2 (CrCH), 92.8 (CrCH), 109.8
(CrC), 113.1 (CrC), 126.4 (ArCH), 127.7 (ArCH), 127.7
(ArCH), 128.5 (ArCH), 143.0 (ArC), 146.1 (ArC) and 232.5
(3CO); m/z (EI) 454 (Mϩ, 9%), 370 [(M Ϫ 3CO)ϩ, 56%]
(HRMS: found Mϩ, 454.0309. Requires M, 454.0331).
The enantiomeric excess of complex 36 was determined to be
95% by using a Chiralcel OD column, with 95:5, hexane–IPA
as eluent. Flow rate 1 ml minϪ1. Detection 256 nm. Retention
time 15.5 min (major) and 27.5 (minor).
50.35; H, 3.52%); νmax (CHCl3)/cmϪ1 1971 and 1897 (C᎐O);
᎐
᎐
δH (250 MHz, CDCl3) 1.59 (3H, d, J 7, CH3), 3.86 (1H, d, JAB
Enantiomerically pure material {[α]D22 Ϫ125 (c 0.98 in CHCl3);
ee ≥99%} could be obtained by recrystallisation from Et2O–
light petroleum (75% recovery).
14, SCHH), 4.24 (1H, d, JAB 14, SCHH), 4.34 (1H, q, J 7,
SCH), 5.26 (2H, m, CrCH) and 5.42–5.48 (2H, m, CrCH);
δC (68 MHz, CDCl3) 26.4 (CH3), 35.8 (CH2), 47.6 (CH), 89.7
(CrCH), 90.3 (CrCH), 91.4 (CrCH), 91.6 (CrCH), 111.0 (CrC),
Preparation of (1S,3ЈS)-tricarbonyl(η6-1-allyl-1,3-dihydro-
isobenzothiophene)chromium(0) 37. The above typical protocol
J. Chem. Soc., Perkin Trans. 1, 1999, 3177–3189
3187

View Article Online
was followed, using 0.2 g of 6. Flash column chromatography
on silica gel (15–25% EtOAc–light petroleum) gave complex 37
as a yellow oil (173 mg, 75%), [α]D23 Ϫ159 (c 4.3 in CHCl3); νmax
(CH3), 31.7 (CH2), 36.8 (CH2), 56.2 (CH), 124.2 (ArCH), 124.8
(ArCH), 126.8 (ArCH), 126.9 (ArCH), 140.6 (ArC) and 144.3
(ArC); m /z (EI) 164 (Mϩ, 10%), 135 [(M Ϫ CH2CH3)ϩ, 100%].
(CHCl3)/cmϪ1 1960 and 1866 (C᎐O); δ (400 MHz, CDCl ) 2.61
᎐
᎐
H
3
(2H, m, CH2), 3.80 (1H, d, JAB 14, SCHH), 4.17 (1H, dd, JAB 14
and JH-H 2, SCHH), 4.30 (1H, m, 2, SCH), 5.12 (2H, m,
(iii) Preparation of (1S)-1-benzyl-1,3-dihydroisobenzothio-
phene 41. The general procedure was followed, using enantio-
merically enriched complex 35 (0.39 g). Purification by
Kugelrohr distillation (200 ЊC/1 mbar) gave 41 as a colourless
oil (0.20 g, 84%); [α]2D3 Ϫ70 (c 0.5 in CHCl3) (Found: C, 79.73;
H, 6.33; S, 14.09. Requires C, 79.62; H, 6.24; S, 14.14%); νmax
(CHCl3)/cmϪ1 2906 and 1730; δH (400 MHz, CDCl3) 3.03 (1H,
dd, JAB 14 and 9, CHHPh), 3.34 (1H, dd, JAB 14 and 5,
CHHPh), 4.08 (2H, m, SCH2), 4.91 (1H, m, SCH) and 7.21
(4H, m, ArH); δC (68 MHz, CDCl3) 36.5 (CH2), 45.1 (CH2),
55.3 (CH), 124.3 (ArCH), 124.7 (ArCH), 126.4 (ArCH), 126.5
(ArCH), 127.0 (ArCH), 128.1 (ArCH), 129.3 (ArCH), 138.8
(ArC), 140.7 (ArC) and 143.5 (ArC); m/z (EI) 226 (Mϩ, 1%),
135 [(M Ϫ PhCH2)ϩ, 100%] (HRMS: found Mϩ, 226.0815.
C15H14S requires M, 226.0816).
4
CrCH), 5.26 (2H, m, CrCH), 5.46 (2H, d, J 6, CH᎐CH ) and
᎐
2
5.82 (1H, m, CH᎐CH ); δ (100 MHz, CDCl ) 35.8 (CH ), 43.7
᎐
2
C
3
2
(CH2), 52.3 (CH2), 89.7 (CrCH), 90.6 (CrCH), 91.4 (CrCH),
111.2 (CrC), 114.0 (CrC), 118.9 (CH2), 133.8 (CH) and 232.3
(3CO); m/z (EI) 312 (Mϩ, 27%), 256 [(M Ϫ 2CO)ϩ, 14%], 228
[(M Ϫ 3CO)ϩ, 72%] (HRMS: found Mϩ, 311.9905. C14H12O3-
SCr requires M, 311.9912).
Preparation of (1S,3ЈS)-tricarbonyl[η6-1-(2-naphthylmethyl)-
1,3-dihydroisobenzothiophene]chromium(0) 38. The above typi-
cal protocol was followed, using 1.10 g of 6. Flash column
chromatography on silica gel (10–20% EtOAc–light petroleum)
gave complex 38 as a yellow solid (1.48 g, 89%), mp 148 ЊC; [α]D23
Ϫ250 (c 0.74 in CHCl3) (Found: C, 63.90; H, 3.87. C22H16O3SCr
requires C, 64.07; H, 3.91%); νmax (CHCl3)/cmϪ1 1971 and 1900
᎐
(C᎐O); δ (400 MHz, CDCl3) 3.23 (1H, dd, J 7 and JAB 14,
᎐
H
(iv) Preparation of (1S)-1-allyl-1,3-dihydroisobenzothiophene
42. The general procedure was followed, using enantiomerically
enriched complex 37 (0.39 g). Purification by Kugelrohr distil-
lation (100 ЊC/ 3 mbar) gave 42 as a colourless oil (22 mg, 79%)
[α]D23 Ϫ73 (c 1.18 in CHCl3); νmax (CHCl3)/cmϪ1 2902, 2253 and
CHH), 3.32 (1H, dd, J 7 and JAB 14, CHH2), 3.63 (1H, d, JAB
14, SCHH), 3.82 (1H, d, JAB 14, SCHH), 4.54 (1H, dd, J 7, 7,
SCH), 5.10 (2H, m, CrCH), 5.22 (1H, m, CrCH), 5.34 (1H, d,
J 6, CrCH), 7.26 (1H, m, ArH), 7.46 (2H, m, ArH), 7.57 (1H,
m, ArH), 7.75 (2H, m, ArH) and 7.82 (1H, m, ArH); δC (68
MHz, CDCl3) 35.5 (CH2), 45.5 (CH2), 53.6 (CH), 89.7 (CrCH),
90.0 (CrCH), 90.2 (CrCH), 91.4 (CrCH), 111.2 (CrC), 113.7
(CrC), 125.8 (ArCH), {(126.2, 127.6, 127.6, 127.8, 127.9,
128.5), ArCH}, 132.3 (ArC), 133.2 (ArC), 134.5 (ArC) and
232.3 (3CO); m/z (EI) 412 (Mϩ, 10%), 328 [(M Ϫ 3CO)ϩ, 13%];
(HRMS: found Mϩ, 412.0229. Requires M, 412.0225).
1794; δH (400 MHz, CDCl ) 2.54 (1H, m, CHHCH᎐CH ), 2.79
᎐
3
2
(1H, m, CHHCH᎐CH ), 4.17 (1H, d, JAB 14, SCHH), 4.23 (1H,
᎐
2
d, JAB 14, SCHH), 4.72 (1H, m, SCH), 5.10 (2H, m, CH᎐CH ),
᎐
2
5.86 (1H, m, CH᎐CH ) and 7.22 (4H, m, ArH); δ (100 MHz,
᎐
2
C
CDCl3) 36.8 (CH2), 42.9 (CH2), 53.6 (CH), 117.4 (CH2), 124.3
(ArCH), 124.9 (ArCH), 126.8 (ArCH), 127.1 (ArCH), 135.4
(CH), 140.7 (ArC) and 143.7 (ArC); m/z (EI) 176 (Mϩ, 0.2%),
135 [(C8H7S)ϩ, 43%] (HRMS: found Mϩ, 176.0643. C11H12S
requires M, 176.0660).
The enantiomeric excess of complex 38 was determined to be
95% using a Chiralcel OD column, with 94:6 hexane–IPA as
eluent. Flow rate 1 ml minϪ1. Detection 256 nm. Retention time
43.5 min (minor) and 50.4 min (major).
(v) Preparation of (1S)-1-(2-naphthyl)-1,3-dihydroisobenzo-
thiophene 43. The general procedure was followed, using enan-
tiomerically pure complex 38 (0.10 g). Purification by flash
column chromatography on silica gel (10% EtOAc–light petrol-
eum) gave 43 as a white solid (58 mg, 86%), [α]D23 Ϫ91 (c 0.23 in
CHCl3); νmax (CHCl3)/cmϪ1 2906 and 1731; δH (400 MHz,
CDCl3) 3.19 (1H, dd, JAB 14 and 9, CH2), 3.50 (1H, dd, JAB 14
and 5, CH2), 4.08 (2H, m, SCH2), 5.02 (1H, m, SCH), 7.20 (4H,
m, ArH), 7.44 (3H, m, ArH), 7.64 (1H, s, ArH) and 7.78 (3H,
m, ArH); δC (100 MHz, CDCl3) 36.7 (CH2), 45.5 (CH2), 55.5
(CH), 124.5 (ArCH), {(125.0, 125.5, 126.0, 126.7, 127.2, 127.7,
127.8, 127.9, 128.0), ArCH}, {(132.4, 133.5, 136.6, 140.9,
143.7), ArC}; m/z (EI) 276 (Mϩ, 0.1%), 135 [(C8H7S)ϩ, 100%]
(HRMS: found Mϩ, 276.0961. C19H16S requires M, 276.0973).
Enantiomerically pure material {[α]D23 Ϫ264 (c 0.70 in CHCl3),
i
ee ≥99%} could be obtained by recrystallisation from PrOH
(76% recovery).
Demetallation of chromium complexes to give enantiomerically
enriched sulfides 39–43
(i) Typical procedure: preparation of (1S)-1-methyl-1,3-
dihydroisobenzothiophene 39.24 A solution of enantiomerically
pure complex 33 (24 mg, 0.08 mmol) in dichloromethane (10
ml) was exposed to sunlight for 12 h. After this time a green
precipitate had formed. The solvent was removed under
reduced pressure and the residue was dissolved in ethyl acetate
(20 ml) and filtered through a pad of Celite. After removal of
the solvent, the residue was purified by Kugelrohr distillation
(85 ЊC/1 mbar) to give 39 as a colourless oil (11 mg, 88%), [α]D23
Ϫ140 (c 0.012 in CHCl3); νmax (CHCl3)/cmϪ1 2962 and 2864;
δH (400 MHz, CDCl3) 1.63 (3H, d, J 7, CH3), 4.19 (1H, d, JAB
14, SCHH), 4.25 (1H, dd, JAB 14, SCHH), 4.72 (1H, q, J 7,
SCH) and 7.21 (4H, m, ArH); δC (100 MHz, CDCl3) 24.3
(CH3), 36.9 (CH2), 48.2 (CH), 123.8 (ArCH), 124.7 (ArCH),
126.8 (ArCH), 126.9 (ArCH), 140.2 (ArC) and 145.6 (ArC);
m/z (EI) 150 (Mϩ, 31%), 135 [(M Ϫ CH3)ϩ, 100%] (HRMS:
found Mϩ, 150.0507. C9H10S requires M, 150.0503).
Crystal structure determination of 3‡
A crystal was mounted on a glass fibre and transferred into the
cold stream of the diffractometer’s low temperature device.
Crystal data. C24H23CrO4PSi, M = 486.5, tetragonal, a =
12.69(2), c = 29.55(5) Å, U = 4759(13) Å3, T = 150(2) K, space
group P41212 (No. 92), Z = 8, Dc = 1.358 g cmϪ3, µ(Mo-Kα) =
0.625 mmϪ1, 9031 reflections measured (including Friedel
opposites), 4185 unique (Rint 0.123), 4185 used in all calcu-
lations. Final R1 [3191 F > 4σ(F)] = 0.0536 and wR(all F2) was
0.108. The Flack parameter refined to Ϫ0.04(4).25
(ii) Preparation of (1S)-1-ethyl-1,3-dihydroisobenzothiophene
40.24 The general procedure was followed, using enantio-
merically enriched complex 34 (17.2 mg). Purification by
Kugelrohr distillation (60 ЊC/0.25 mbar) gave 40 as a colourless
oil (7 mg, 70%) [α]D23 Ϫ60 (c 0.33 in CHCl3); νmax (CHCl3)/cmϪ1
2964 and 2253; δH (400 MHz, CDCl3) 1.03 (3H, t, J 7, CH3),
1.79 (1H, m, CHHCH3), 2.05 (1H, m, CHHCH3), 4.19 (1H, d,
JAB 14, SCHH), 4.24 (1H, dd, JAB 14, SCHH) 4.63 (1H, m,
SCH) and 7.23 (4H, m, ArH); δC (100 MHz, CDCl3) 11.7
Crystal structure determination of 21
A crystal was mounted on a glass fibre and transferred into the
cold stream of the diffractometer’s low temperature device.
‡ CCDC reference number 207/356. See http://www.rsc.org/suppdata/
p1/1999/3177 for crystallographic files in .cif format.
3188
J. Chem. Soc., Perkin Trans. 1, 1999, 3177–3189

View Article Online
3 K. Schellhaas, H.-G. Schmalz and J. W. Bats, Chem. Eur. J., 1998, 4,
Crystal data. C28H21CrO4P, M = 504.42, triclinic, a =
10.820(2), b = 11.206(2), c = 14.618(2) Å, α = 75.33(3), β =
86.12(2), γ = 78.60(2)Њ, U = 1680.5(5) Å3, T = 150(2) K, space
57.
4 A. Ariffin, A. J. Blake, W.-S. Li and N. S. Simpkins, Synlett, 1997,
1453.
5 For a recent review, see (a) C. Bolm and K. Muniz, Chem. Soc. Rev.,
1999, 28, 51; (b) C. Bolm, K. Muniz and C. Ganter, New. J. Chem.,
1998, 1371; (c) S. U. Son, H.-Y. Jang, I. S. Lee and Y. K. Chung,
Organometallics, 1998, 17, 3236; (d) J. W. Han, S. U. Son and
Y. K. Chung, J. Org. Chem., 1997, 62, 8264.
6 R. A. Ewin and N. S. Simpkins, Synlett, 1996, 317.
7 A. Ariffin, A. J. Blake, R. A. Ewin and N. S. Simpkins, Tetrahedron:
Asymmetry, 1998, 2563.
8 (a) E. M. L. Cowton, S. E. Gibson, M. J. Schneider and M. H.
Smith, Chem. Commun., 1996, 839; (b) S. E. Gibson, P. C. V. Potter
and M. H. Smith, Chem. Commun., 1996, 2757; (c) S. E. Gibson,
P. Ham, G. R. Jefferson and M. H. Smith, J. Chem. Soc., Perkin
Trans. 1, 1997, 2161, See also reference 20 and references therein.
9 K. Bambridge, M. J. Begley and N. S. Simpkins, Tetrahedron Lett.,
1994, 35, 3391.
10 R. A. Ewin, A. M. MacLeod, D. A. Price, N. S. Simpkins and
A. P. Watt, J. Chem. Soc., Perkin Trans. 1, 1997, 401.
11 C. A. L. Mahaffy and P. L. Pauson, Inorg. Synth., 1979, 19, 154.
12 J. A. Bowden and R. Colton, Aust. J. Chem., 1973, 26, 43.
13 V. I. Losilkina, M. N. Estekhina, N. K. Baranetskaya and V. N.
Setkina, J. Organomet. Chem., 1986, 299, 187.
14 D. Price and N. S. Simpkins, Tetrahedron Lett., 1995, 36, 6135.
15 For examples of the types of conditions tried, see (a) P. O’Brien
and S. Warren, Synlett, 1996, 579; (b) A. P. Dishington, R. E.
Douthwaite, A. Mortlock, A. B. Muccioli and N. S. Simpkins,
J. Chem. Soc., Perkin Trans. 1, 1997, 323.
16 S. G. Davies, T. Loveridge and J. M. Clough, J. Chem. Soc., Chem.
Commun., 1995, 817.
17 T. Coumbe, N. J. Lawrence and F. Muhammad, Tetrahedron Lett.,
1994, 35, 625.
18 For a review, see N. Miyaura and A. Suzuki, Chem. Rev., 1995, 95,
2457.
19 N. S. Simpkins, in Advances in Asymmetric Synthesis, ed. G. R.
Stephenson, Blackie Academic, London, 1996.
20 S. E. Gibson, P. O’Brien, E. Rahimian and M. H. Smith, J. Chem.
Soc., Perkin Trans. 1, 1999, 909.
21 V. K. Aggarwal, Synlett, 1998, 329.
22 N. J. Archer, C. M. Rayner, D. Bell and D. Miller, Synlett, 1994,
617.
23 G. A. Cran, C. L. Gibson, S. Handa and A. R. Kennedy, Tetra-
hedron: Asymmetry, 1996, 7, 2511.
group P1 (No. 2), Z = 2, Dc = 0.997 g cmϪ3, µ(Mo-Kα) = 0.411
¯
mmϪ1, 10515 reflections, 5907 unique (Rint 0.023), 5907 used in
all calculations. Final R1 [5017 F > 4σ(F)] = 0.0468 and wR(all
F2) was 0.115. The values for M, Dc and µ ignore the contents
of an ill-defined solvent region which was modelled using the
SQUEEZE option in PLATON98.26
Crystal structure determination of 33
A crystal was mounted on a glass fibre in a file of perfluoro-
polyether oil and transferred into the cold stream of the
diffractometer’s low temperature device.
Crystal data. C12H10CrO3S, M = 286.3, monoclinic, a =
6.581(6), b = 8.758(9), c = 10.333(8) Å, β = 93.88(8)Њ, U =
594.2(7) Å3, T = 150(2) K, space group P21 (No. 4), Z = 2,
Dc = 1.600 g cmϪ3, µ(Mo-Kα) = 1.129 mmϪ1, 2082 reflections
measured (including Friedel opposites), 1971 unique (Rint
0.021), 1971 used in all calculations. Final R1 [1952 F >
4σ(F)] = 0.0283 and wR(all F2) was 0.0785. The Flack param-
eter refined to Ϫ0.02(2).25
Acknowledgements
We are grateful to the University of Malaya (Lembah Pantai,
59100 Kuala Lumpur, Malaysia) for financial support of A. A.
through the SLAB scheme. We also acknowledge the Engineer-
ing and Physical Sciences Research Council (EPSRC) for
funding for a diffractometer and for a postdoctoral award to
W.-S. L.
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3189