Scope and limitations of the Peterson olefination reaction as a route to vinylidene phosphanes

Article abstract of DOI:10.1002/ejoc.200300683

The Peterson olefination reaction has been investigated as a route to novel P-substituted alkenes. The reaction between [(nPr₂P) ₂(Me₃Si)C]Li and paraformaldehyde cleanly gives the symmetrical vinylidene phosphane (nPr₂P)₂C=CH₂ (4) in good to excellent yields. In contrast, reactions between [(R ₂P)(Me₃Si)₂C]Li (R = Me, nPr) and paraformaldehyde yield complex mixtures of products which do not contain the expected vinylidene species. However, the unsymmetrical vinylidene phosphanes [nPr₂P(BH₃)](Me₃Si)C=CH₂ (6), (Ph₂P)(iPr₂P)C=CH₂ (7), [nPr ₂P(S)](Me₃Si)C=CH₂ (10), [Ph ₂P(S)][iPr₂P(S)]C=CH₂ (11) and [Ph ₂P(S)][Me₂P(S)]C=CH₂ (12) are readily accessible by the Peterson olefination reaction {compound 7 is obtained by deprotection of the corresponding borane adduct [Ph₂P(BH ₃)][iPr₂P(BH₃)]C=CH₂ with pyrrolidine}. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejoc.200300683

FULL PAPER
Scope and Limitations of the Peterson Olefination Reaction as a Route to
Vinylidene Phosphanes
Keith Izod,*[a] William McFarlane,[a] and Brent V. Tyson[a]
Keywords: Olefination / Phosphorus / Peterson / Protecting groups
The Peterson olefination reaction has been investigated as a
route to novel P-substituted alkenes. The reaction between
[(nPr2P)2(Me3Si)C]Li and paraformaldehyde cleanly gives
the symmetrical vinylidene phosphane (nPr2P)2C=CH2 (4) in
good to excellent yields. In contrast, reactions between
[(R2P)(Me3Si)2C]Li (R = Me, nPr) and paraformaldehyde yield
complex mixtures of products which do not contain the ex-
pected vinylidene species. However, the unsymmetrical vi-
nylidene phosphanes [nPr2P(BH3)](Me3Si)C=CH2 (6),
(Ph2P)(iPr2P)C=CH2 (7), [nPr2P(S)](Me3Si)C=CH2 (10),
[Ph2P(S)][iPr2P(S)]C=CH2 (11) and [Ph2P(S)][Me2P(S)]C=CH2
(12) are readily accessible by the Peterson olefination reac-
tion {compound 7 is obtained by deprotection of the corres-
ponding borane adduct [Ph2P(BH3)][iPr2P(BH3)]C=CH2 with
pyrrolidine}.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2004)
Introduction
Polyphosphanes such as the tripodal triphosphane
MeC(CH2PPh2)3 are excellent ligands for the stabilization
of low oxidation state transition metal complexes, many of
which act as (pre-)catalysts for important organic trans-
formations;[1] for example, the bimetallic complex rac-
[{[Et2PCH2CH2P(Ph)]2CH2}Rh2(norbornadiene)2][BF4]2 is
a highly efficient pre-catalyst for the regioselective hydrofor-
mylation of α-olefins.[2] Diphosphanes in which the two
phosphorus atoms are separated by a single carbon such as
(Ph2P)2CH2 (dppm) and (Me2P)2CH2 (dmpm) are also of
enormous value and form a particularly useful sub-class of
‘‘A-frame’’ ligands which are able to support bi- and poly-
nuclear transition metal complexes.[3]
Scheme 1
Although we have successfully employed this method-
ology for the synthesis of a range of new polyphosphanes,
this reaction potentially suffers from the drawback that
there have, until now, been few readily available vinylidene
phosphane precursors. When we began this work only the
diphosphanes (Ph2P)2CϭCHR [R ϭ H (1a), Ph (1b)] and
the corresponding disulfides [Ph2P(S)]2CϭCHR [R ϭ H
(2a), Ph (2b)] had been reported. The diphosphane 1a may
be prepared in moderate yield from the reaction between
Ph2PLi and vinylidene chloride (Scheme 2).[5]
We have recently become interested in the synthesis of
new polyphosphane ligands I and II, the former of which
incorporate the PϪCϪP unit found in dppm and dmpm.
These new ligands are prepared by a Schlenk dimerization
protocol from vinylidene phosphanes of the form
(R2P)R1CϭCH2 (R1 ϭ e.g. R2P, R22P, Me3Si), according
to Scheme 1.[4]
Scheme 2
This reaction is suitable only for the synthesis of sym-
metrical vinylidene phosphanes and is limited to examples
where the lithium phosphanide precursor is readily access-
ible. In our hands this reaction has failed to give significant
quantities of vinylidene phosphanes with substituents other
[a]
Chemistry, School of Natural Sciences, University of Newcastle,
Newcastle upon Tyne, NE1 7RU, UK
Fax: (internat.) ϩ 44-(0)191-222-6929
E-mail: k.j.izod@ncl.ac.uk
Eur. J. Org. Chem. 2004, 1043Ϫ1048
DOI: 10.1002/ejoc.200300683
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K. Izod, W. McFarlane, B. V. Tyson
FULL PAPER
than phenyl at the phosphorus center, most likely due to
the ready anionic polymerization of vinylidene species. For
example, the reaction between two equivalents of Cy2PLi
and vinylidene chloride under the same conditions em-
ployed in the synthesis of (Ph2P)2CϭCH2 gave only an in-
tractable sticky solid which was free of the desired vinyl-
idene phosphane (Cy2P)2CϭCH2 (Cy ϭ cyclohexyl).
Grim and Goli have reported the synthesis of 2a and 2b
by the reaction of [{Ph2P(S)}2CH]Li with either paraform-
aldehyde or benzaldehyde, respectively.[6] The correspond-
ing diphosphanes 1 were obtained from the disulfides by
treatment with Si2Cl6. We have found that, where the sub-
stituents at phosphorus are other than phenyl, similar reac-
tions between phosphane-substituted organolithiums and
paraformaldehyde do not yield the corresponding vinyl-
idene phosphanes.
Scheme 4
The Peterson olefination of PV-substituted carbanions is
more established:[9] Savignac and co-workers have used the
Peterson reaction for the synthesis of α-fluorovinylphos-
phonates,[11] whereas Collignon and co-workers have used
this reaction for the synthesis of phosphonate-substituted
penta-1,3-dienes.[12]
We now report the use of a relatively straightforward Pet-
erson olefination protocol for the synthesis of a range of
vinylidene phosphanes and vinylidene phosphane sulfides.
In order to increase the range and availability of vinyl-
idene phosphanes we have initiated a study into their syn-
thesis by a relatively straightforward Peterson olefination
protocol. The Peterson olefination reaction is one of a
group of several olefination protocols dependent on the
elimination of a heteroatom-containing leaving group from
Results and Discussion
Treatment of the symmetrical diphosphane (nPr2P)2CH2
with one equivalent of tBuLi, followed by one equivalent
of Me3SiCl yields the corresponding α-silyl-substituted di-
phosphane (nPr2P)2(Me3Si)CH (3) (Scheme 5). Reaction of
3 with one equivalent of tBuLi, followed by an excess of
paraformaldehyde gives, after a simple aqueous workup, the
corresponding vinylidene phosphane (nPr2P)2CϭCH2 (4) in
good yield (Table 1). Compound 4 is isolated as a colorless,
volatile oil, which may be purified by distillation under re-
duced pressure.
a
heteroatom-stabilized ‘‘carbanion’’, which includes
Wittig, HornerϪWittig, HornerϪWadsworthϪEmmons
(HWE) and Julia olefinations (Scheme 3).[7]
Scheme 5. (i) tBuLi, light petroleum 16 h; (ii) Me3SiCl, Ϫ78 °C 2 h;
(iii) CH2O 1 h, then H2O
Attempts to prepare the corresponding vinylidene phos-
phanes (R2P)2CϭCH2 [R ϭ Cy or iPr] by this method
failed; after an aqueous workup we were able to recover
only the silyl-substituted starting materials (R2P)2(Me3Si)-
Scheme 3
It has been demonstrated, that in substrates where com- CH (R ϭ Cy, iPr) from these reactions. We attribute this
petitive Peterson and HornerϪWittig/HWE or Julia elimin- failure to the steric demands of the substituents at phos-
ations may take place, it is the Peterson reaction which phorus, which are likely to hinder nucleophilic attack by the
dominates.[8,9]
[{(EtO)2P(O)}(MeS)(Me3Si)C]Li with aldehydes gives the tionality.
For
example,
the
reaction
of sterically crowded carbanion center at the carbonyl func-
Peterson olefination product as the (E)-isomer in good
In contrast to the facile formation of 4, attempts to
yields (Scheme 4).[9] However, although the Peterson olefin- prepare the unsymmetrical vinylidene phosphanes
ation reaction is an excellent method for the synthesis of (R2P)(Me3Si)CϭCH2 [R ϭ Me, nPr] by Peterson olefin-
variously substituted alkenes, this methodology has been ation of the corresponding bis(silyl)-stabilized carbanions
applied to the synthesis of phosphorus()-substituted al- (R2P)(Me3Si)2CϪ were unsuccessful. Treatment of
kenes to only a limited extent. This is in spite of the fact [(R2P)(Me3Si)2C]Li with paraformaldehyde in THF or light
that Peterson himself reported the syntheses of the vinyl- petroleum at room temperature, followed by an aqueous
phosphanes Ph2PCHϭCR1R2 [R1 ϭ Ph; R2 ϭ H, Ph] and workup with de-gassed water and removal of solvent in va-
the vinylphosphane sulfide Ph2P(S)CHϭCPh2 in moderate cuo, gave a colorless oil containing a complex mixture of
1
yields in his original paper on silyl-based olefinations in products (Scheme 6). A H NMR spectrum of the crude
1968.[10]
product mixture (R ϭ nPr) indicated the presence of a small
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Scope and Limitations of the Peterson Olefination Reaction
Table 1. Isolated vinylidene phosphanes
FULL PAPER
a colorless oil which was identified as the vinylphosphane
nPr2PCHϭCH2 (5). Analysis of the crude reaction mixture,
after treatment with elemental sulfur, by GC-MS indicates
that 5 is formed in approximately 57% yield in this reaction,
along with about 20 further products. At lower tempera-
tures this reaction fails to proceed at all: when the reaction
between [(nPr2P)(Me3Si)2C]Li and paraformaldehyde was
carried out at either Ϫ20 or Ϫ78 °C only the starting mate-
rial (nPr2P)(Me3Si)2CH was recovered.
The isolation of the vinylphosphane 5 from this reaction
is somewhat unexpected, especially in light of the facile for-
mation of 4 and the previously reported high yield synthesis
of the vinylidene silane (Me3Si)2CϭCH2 by the Peterson
olefination of (Me3Si)3CLi with paraformaldehyde.[13] In
this regard, it is interesting to note that Grim and Goli re-
port that the reaction between [{Ph2P(S)}2CH]K and
paraformaldehyde gives the vinylphosphane sulfide
[Ph2P(S)]CHϭCH2 rather than the expected vinylidene
species.[6]
Whereas attempts to prepare (nPr2P)(Me3Si)CϭCH2
by a Peterson olefination protocol failed, the reaction
between the corresponding phosphane-borane derivative
[{nPr2P(BH3)}(Me3Si)2C]Li and paraformaldehyde gave the
borane-protected vinylidene phosphane [nPr2P(BH3)]-
(Me3Si)CϭCH2 (6) in high yield (Scheme 6). Unfortunately,
due to the strongly basic nature of the phosphane moiety,
attempts to remove the borane protecting group from this
compound using either Et2NH or pyrrolidine were unsuc-
cessful. It has been reported previously that α-lithiated
phosphane-borane complexes behave similarly to α-lithiated
phosphane oxides and undergo Horner-type elimination on
treatment with aldehydes to give the corresponding al-
kenes.[14] The reaction between [{nPr2P(BH3)}(Me3Si)2C]Li
and paraformaldehyde may, therefore, proceed by either a
Peterson or a HornerϪWittig-type olefination pathway to
give a phosphane-substituted or a silyl-substituted alkene,
respectively (Scheme 6). However, we see no evidence for
the HornerϪWittig product in this reaction, consistent with
previous observations on substrates where competitive
Horner and Peterson olefinations may take place.[9]
amount of unchanged starting material, (nPr2P)(Me3Si)2-
CH, along with other species containing nPr2P, SiMe3 and
vinyl fragments. The 31P{1H} NMR spectrum of this mix-
ture contains numerous peaks, with major signals at Ϫ43.2,
Ϫ28.8 and Ϫ28.0 ppm. There is no evidence for the ex-
The unsymmetrical vinylidene bis(phosphane) (Ph2P)-
pected vinylidene phosphane (nPr2P)(Me3Si)CϭCH2 or for (iPr2P)CϭCH2 (7) is accessible by the Peterson olefination
species containing PV. Flash distillation of the crude reac- of in situ-generated [Ph2P(BH3)][iPr2P(BH3)](Me2HSi)-
tion mixture under reduced pressure (20 °C, 0.1 Torr) gave C]Li (8) with paraformaldehyde and subsequent deprotec-
Scheme 6
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K. Izod, W. McFarlane, B. V. Tyson
FULL PAPER
˚
freeze-pump-thaw cycles and stored over activated 4-A molecular
tion of the adduct [Ph2P(BH3)][iPr2P(BH3)]CϭCH2 (9) with
pyrrolidine (Scheme 7). We find that the use of the less steri-
cally demanding dimethylsilyl substituent in the organoli-
thium compound gives greater yields of 7 and that simply
stirring the borane adduct with pyrrolidine for 12 h results
in deprotection of both phosphane functionalities. We attri-
bute the ease with which the borane protecting group may
be removed in this case to the steric bulk of the phos-
phane substituents.
sieves. Organolithiums were obtained from Aldrich, nBuLi as a 2.5
 solution in hexanes, tBuLi as a 1.7  solution in pentane;
nPrMgCl was obtained from Aldrich as a 2.0  solution in diethyl
ether. The adduct Me2SBH3 was obtained as a 2.0  solution in
diethyl ether. Potassium tert-butoxide was purchased from Lancas-
ter and heated under vacuum at 100 °C (10Ϫ3 Torr) for 4 h prior
to use. Paraformaldehyde was heated under vacuum at 100 °C
(10Ϫ3 Torr) prior to use. The compounds (Me3Si)2CHPCl2
and
[14]
[15]
CH2(PCl2)2
were prepared by previously published procedures.
All other compounds were used as supplied.
1H and 13C NMR spectra were recorded with a Bruker AC200 or
a JEOL Lambda500 spectrometer operating at 200.1, 500.1, 50.3
and 125.6 MHz, respectively. 31P NMR spectra were recorded with
a Bruker WM300 spectrometer operating at 121.5 MHz. 1H and
13C chemical shifts are quoted in ppm relative to tetramethylsilane
and 31P chemical shifts are quoted relative to external 85% H3PO4.
Elemental analyses were obtained by the microanalysis service at
London Metropolitan University, UK.
Preparation of (nPr2P)2CH2: To a cold (Ϫ78 °C) solution of
CH2(PCl2)2 (10.54 g, 48.40 mmol) in diethyl ether (100 mL) was
added nPrMgCl (96.80 mL, 0.193 mol), dropwise. The solution was
allowed to attain room temperature and was stirred for 12 h. De-
oxygenated water (3 ϫ 50 mL) was added and the organic layer
Scheme 7. (i) 2 BH3SMe2, diethyl ether, 1 h; (ii) nBuLi, THF, 12 h;
(iii) Me2HSiCl, diethyl ether/THF, Ϫ78 °C; (iv) CH2O, 1 h, then
H2O; (v) pyrrolidine, 16 h, 20 °C
˚
was dried with activated 4-A molecular sieves. Solvent was removed
in vacuo to give the diphosphane (nPr2P)2CH2. Isolated yield
1
9.70 g, 81%. H NMR (CDCl3, 25 °C): δ ϭ 0.92Ϫ1.49 (m, 28 H,
Pr), 2.28 (s, 2 H, PCH2P) ppm. 13C{1H} NMR (CDCl3, 25 °C):
δ ϭ 16.00 (Pr), 19.23 (Pr), 25.37 (PCH2P), 31.16 (Pr) ppm. 31P{1H}
NMR (CDCl3, 25 °C): δ ϭ Ϫ35.6 ppm.
In spite of the apparent problems associated with the syn-
thesis of unsymmetrical vinylidene phosphanes, the Peter-
son olefination methodology may readily be employed for
the synthesis of PV-substituted alkenes.[9,11,12,15] The phos-
phane sulfide derivative [{nPr2P(S)}(Me3Si)2C]Li reacts
rapidly with paraformaldehyde to give the corresponding
vinylidene compound [nPr2P(S)](Me3Si)CϭCH2 (10) in
good yield (Scheme 6). Similarly, the related compounds
[Ph2P(S)][iPr2P(S)]CϭCH2 (11) and [Ph2P(S)][Me2P(S)]Cϭ
CH2 (12) may be synthesized by this methodology (Table 1).
Once again, there is no evidence for the HornerϪWittig ole-
fination products in these reactions.
In summary, we have found that the Peterson olefination
of phosphorus-substituted organolithiums proceeds cleanly
to give symmetrically substituted vinylidene phosphanes,
but that this reaction is more complicated for unsymmetri-
cal systems. Unsymmetrical phosphorus-substituted alkenes
are accessible when the phosphorus substituent is in the
higher PV oxidation state or when the PIII center is bor-
ane-protected.
Preparation of (nPr2P)2C؍CH2 (4): To a solution of the diphos-
phane (nPr2P)2CH2 (6.06 g, 24.50 mmol) in light petroleum
(20 mL) was added tBuLi (14.41 mL, 24.50 mmol) and this solution
was stirred overnight. The resulting white slurry was added drop-
wise to chlorotrimethylsilane (3.11 mL, 24.50 mmol) at Ϫ78 °C and
allowed to stir for 2 h. The resulting solution was filtered and the
filtrate was treated with tBuLi (14.41 mL, 24.50 mmol) and stirred
for 12 h before being treated with a large excess of paraformal-
dehyde (4.41 g, 0.147 mol) and stirred for 1 hour. The reaction was
quenched with deoxygenated water (30 mL) and the organic layer
was extracted into diethyl ether (3 ϫ 20 mL) and dried with acti-
˚
vated 4-A molecular sieves. Solvent was removed in vacuo yielding
4 as a colorless, air sensitive oil. Isolated yield 5.12 g, 80%.
C14H30P2 (260.3): calcd. C 64.59, H 11.62; found C 64.69, H 11.52.
1H NMR (CDCl3, 25 °C): δ ϭ 0.80Ϫ1.68 (m, 28 H, Pr), 5.83 (t,
3
3JPHcis ϩ JPHtrans ϭ 30 Hz, 2 H, ϭCH2) ppm. 13C{1H} NMR
(CDCl3, 25 °C): δ ϭ 15.90 (t, JP,C ϭ 6 Hz, Pr), 19.20 (t, JP,C
ϭ
7 Hz, Pr), 28.76 (t, JP,C ϭ 3 Hz, Pr), 149.47 (t, JP,C ϭ 37 Hz, ϭ
CH2) ppm. 31P{1H} NMR (CDCl3, 25 °C): δ ϭ Ϫ23.1 ppm.
Preparation of [nPr2P(BH3)](Me3Si)C؍CH2 (6): To a cold (Ϫ78
°C) solution of (Me3Si)2CHPCl2 (13.63 g, 52.17 mmol) in diethyl
ether (100 mL) was added, dropwise, a solution of nPrMgCl in di-
ethyl ether (52.17 mL, 0.104 mol). The solution was allowed to at-
tain room temperature and was stirred for 12 h. Deoxygenated
water (50 mL) was added and the organic layer was dried with acti-
Experimental Section
General Remarks: All manipulations were carried out using stand-
ard Schlenk techniques under dry nitrogen. Light petroleum (b.p.
40Ϫ60 °C), diethyl ether and THF were distilled from sodium, pot-
assium or sodium/potassium alloy and were stored over a potass-
˚
vated 4-A molecular sieves. Solvent was removed in vacuo to give
crude (nPr2P)(Me3Si)2CH, which was purified by distillation at re-
ium film (with the exception of THF, which was stored over acti-
duced pressure (80 °C, 10Ϫ2 Torr). This phosphane (11.79 g,
˚
vated 4-A molecular sieves). Dichloromethane was distilled from 42.64 mmol) was dissolved in diethyl ether (60 mL), treated with
˚
CaH2 and was stored over activated 4-A molecular sieves. Deuter-
ated chloroform was distilled from CaH2, deoxygenated by three
BH3.SMe2 (21.32 mL, 42.64 mmol) and stirred for 2 h. THF
(20 mL) was added followed by nBuLi (17.06 mL, 42.64 mmol) and
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Scope and Limitations of the Peterson Olefination Reaction
FULL PAPER
this mixture was stirred for 2 h. A large excess of paraformaldehyde
(6.40 g, 0.21 mol) was added and the mixture was stirred for 1 h.
The reaction was then quenched with deoxygenated water (30 mL)
and the organic layer was extracted into diethyl ether (3 ϫ 20 mL)
room temperature and was stirred for 12 h. Deoxygenated water
(50 mL) was added and the organic layer was dried with activated
4-A molecular sieves. Solvent was removed in vacuo to give
(nPr2P)(Me3Si)2CH. This phosphane (2.60 g, 9.41 mmol) was dis-
solved in dichloromethane (10 mL), treated with elemental sulfur
˚
˚
and dried with activated 4-A molecular sieves. Solvent was removed
in vacuo to give 6 as a pale yellow oil. Isolated yield 8.97 g, 75%. (0.30 g, 9.41 mmol) and stirred for 2 h. Solvent was removed in
C11H28BPSi (230.2): calcd. C 57.39, H 12.26; found C 57.34, H vacuo and the product was dissolved in THF (20 mL), treated with
12.00. 1H NMR (CDCl3, 27 °C): δ ϭ 0.24 (s, 9 H, SiMe3), nBuLi (3.76 mL, 9.40 mmol) and stirred for 2 h. A large excess of
0.98Ϫ1.70 (m, 14 H, Pr), 6.38 (dd, JH,H ϭ 3, 3JPH ϭ 44 Hz, 1 H, ϭ
paraformaldehyde (1.41 g, 0.044 mol) was added and this mixture
CH2), 6.57 (dd, JH,H ϭ 3, 3JPH ϭ 27 Hz,1 H, ϭCH2) ppm. 13C{1H} was stirred for 1 h. The reaction was then quenched with deoxygen-
NMR (CDCl3, 27 °C): δ ϭ 0.00 (SiMe3), 15.58 (Pr), 16.46 (Pr), ated water (30 mL) and the organic layer was extracted with diethyl
27.10 (Pr), 144.47 (ϭCH2) ppm. 31P{1H} NMR (CDCl3, 25 °C): ether (3 ϫ 20 mL) and dried with activated 4-A molecular sieves.
˚
δ ϭ 21.9 (br) ppm.
Solvent was removed in vacuo to give 10 as a pale yellow oil. Iso-
1
lated yield 1.86 g, 65%. H NMR (CDCl3, 27 °C): δ ϭ 0.04 (s, 9
Preparation of (Ph2P)(iPr2P)C؍CH2 (7): To a solution of methyldi-
phenylphosphane (4.10 g, 20.48 mmol) in diethyl ether (30 mL) was
added nBuLi (8.36 mL, 20.48 mmol) and this mixture was left to
stir for approximately 1 h. To this orange/yellow solution was ad-
ded, dropwise, a solution of tBuOK (2.30 g, 20.48 mmol) in diethyl
ether (30 mL). The yellow precipitate was isolated by filtration and
washed with diethyl ether (3 ϫ 15 mL) and residual solvent was
removed in vacuo. The solid was dissolved in THF (30 mL) and
added to a cold (Ϫ78 °C) solution of chlorodiisopropylphosphane
(2.92 mL, 18.38 mmol) in THF (20 mL). The solvent was removed
in vacuo to give a viscous brown oil which was dissolved in light
petroleum (40 mL) and washed with deoxygenated water (3 ϫ
3
H, SiMe3), 0.76Ϫ1.55 (m, 14 H, Pr), 6.23 (dd, JH,H ϭ 3, JPH
ϭ
3
51 Hz, 1 H, ϭCH2), 6.67 (dd, JH,H ϭ 3, JPH ϭ 34 Hz, 1 H, ϭ
CH2) ppm. 13C{1H} NMR (CDCl3, 27 °C): δ ϭ 0.54 (SiMe3), 15.26
(Pr), 16.01 (Pr), 35.17 (Pr), 146.20 (ϭCH2) ppm. 31P{1H} NMR
(CDCl3, 25 °C): δ ϭ 52.3 ppm.
Preparation of [Ph2P(S)][iPr2P(S)]C؍CH2 (11): To a solution of
the diphosphane (Ph2P)(iPr2P)CH2 (3.64 g, 11.51 mmol; see 7
above) in dichloromethane (40 mL) was added elemental sulfur
(0.738 g, 11.51 mmol) and this solution was stirred for 2 h. Solvent
was removed in vacuo and the white solid was dissolved in THF
(20 mL), treated with nBuLi (4.60 mL, 11.51 mmol) and left to stir
for 12 h. The deep orange solution was then added, dropwise, to a
cold (Ϫ78 °C) solution of chlorotrimethylsilane (1.49 mL,
11.51 mmol) in diethyl ether (10 mL). The solution was allowed to
attain room temperature and was treated with a further equivalent
of nBuLi (4.60 mL, 11.51 mmol) and stirred for 12 h. To the re-
sulting solution was added solid paraformaldehyde (1.63 g,
54.15 mmol) and diethyl ether (20 mL) and the mixture was al-
lowed to stir for 1 h before deoxygenated water (30 mL) was added.
The organic phase was decanted, the aqueous layer was extracted
into diethyl ether (3 ϫ 10 mL) and the combined organic extracts
˚
20 mL). The organic layer was dried with activated 4-A molecular
sieves and solvent was removed in vacuo to give the diphosphane
(Ph2P)(iPr2P)CH2 as a colorless oil.
To a solution of the diphosphane (Ph2P)(iPr2P)CH2 (3.66 g,
11.57 mmol) in diethyl ether (40 mL) was added BH3·SMe2
(11.57 mL, 23.14 mmol) and this solution was stirred for 1 h. THF
(20 mL) was added, followed by nBuLi (5.03 mL, 11.57 mmol) and
the solution was left to stir for 12 h. The deep orange solution was
added dropwise to a cold (Ϫ78 °C) solution of chlorodimethylsil-
ane (1.28 mL, 11.57 mmol) in diethyl ether (10 mL). The solution
was allowed to attain room temperature and was treated with
nBuLi (5.03 mL, 11.57 mmol) and stirred for 12 h. To the resulting
solution was added paraformaldehyde (1.63 g, 54.15 mmol) and di-
ethyl ether (20 mL), the mixture was allowed to stir for 1 hour and
then deoxygenated water (30 mL) was added. The organic layer was
decanted, the aqueous layer was extracted into diethyl ether (3 ϫ
10 mL) and the combined organic extracts were dried with acti-
˚
were dried with activated 4-A molecular sieves. The solution was
filtered and solvent was removed in vacuo to give a colorless oil
which yielded 11 as a white crystalline solid on addition of ethanol
(20 mL). Isolated yield 2.10 g, 53% (based on Ph2PMe).
C20H26P2S2 (392.5): calcd. C 61.20, H 6.81; found C 60.51, H 6.81.
3
1H NMR (CDCl3, 25 °C): δ ϭ 0.72 [dd, JH,H ϭ 7, JPH ϭ 19 Hz,
3
6 H, CH(CH3)2], 1.08 [dd, JH,H ϭ 7, JPH ϭ 19 Hz, 6 H,
CH(CH3)2], 3.07 [m, 2 H, CH(CH3)2], 6.34 (ddd, JH,H ϭ 1, 3JPH ϭ
22, 3JPH ϭ 37 Hz, 1 H, ϭCH2), 7.40Ϫ7.50 (m, 6 H, Ph), 7.52 (ddd,
˚
vated 4-A molecular sieves. The dried solution was filtered and sol-
3
3
vent was removed in vacuo and a small amount of light petroleum
was added, yielding an off-white, crystalline solid. This solid was
dissolved in pyrrolidine (8.23 g, 0.115 mol) and the solution was
stirred overnight. Excess pyrrolidine was removed in vacuo and the
residue was distilled under reduced pressure (oil bath temperature
JH,H ϭ 1, JPH ϭ 22, JPH ϭ 37 Hz, 1 H, ϭCH2), 7.67Ϫ7.71 (m,
4 H, Ph) ppm. 13C{1H} NMR (CDCl3, 25 °C): δ ϭ 17.89
[CH(CH3)2], 18.18 [CH(CH3)2], 28.89 [CH(CH3)2], 128.72, 130.97,
131.84, 136.26 (Ph), 150.93 (ϭCH2) ppm. 31P{1H} NMR (CDCl3,
25 °C): δ ϭ 42.4 [d, JP,P ϭ 26 Hz, P(S)Ph2], 84.0 (d, JP,P ϭ 26 Hz,
P(S)iPr2) ppm.
150 °C, 0.01 Torr) to give 7 as a colorless oil. Isolated yield 2.85 g,
72%. 1H NMR (CDCl3, 25 °C): δ ϭ 0.94 [dd, JH,H ϭ 7, JP,P
ϭ
3
Preparation of [Ph2P(S)][Me2P(S)]C؍CH2 (12): To a solution of
trimethylphosphane (2.31 g, 30.66 mmol) in light petroleum
(30 mL) was added tBuLi (18.04 mL, 30.66 mmol) and this mixture
was stirred for 12 h. The resulting precipitate was isolated by fil-
tration, washed with light petroleum (3 ϫ 15 mL) and dried in va-
cuo. The solid was dissolved in THF (30 mL) and added to a cold
(Ϫ78 °C) solution of chlorodiphenylphosphane (4.63 mL,
25.81 mmol) in THF (20 mL). The solvent was removed in vacuo
to give a straw-colored oil which was dissolved in light petroleum
(40 mL) and washed with deoxygenated water (3 ϫ 20 mL). The
3
13 Hz, 6 H, CH(CH3)2], 1.03 [dd, JH,H ϭ 7, JP,P ϭ 13 Hz, 6 H,
CH(CH3)2], 1.95 [m, 2 H, CH(CH3)2], 5.58 (ddd, JH,H ϭ 2, 3JPH ϭ
3
3
9, JPH ϭ 19 Hz, 1 H, ϭCH2), 6.06 (ddd, JH,H ϭ 2, JPH ϭ 10,
3JPH ϭ 19 Hz, 1 H, ϭCH2), 7.26 (m, 10 H, Ph) ppm. 13C{1H}
NMR (CDCl3, 25 °C): δ ϭ 19.57 [CH(CH3)2], 22.82 [CH(CH3)2],
53.67 [CH(CH3)2] 128.10, 128.53, 134.13, 135.76 (Ph), 150.93 (ϭ
CH2) ppm. 31P{1H} NMR (CDCl3, 25 °C): δ ϭ Ϫ4.4 (d, JP,P
102 Hz, PiPr2), 15.4 (d, JP,P ϭ 102 Hz, PPh2) ppm.
ϭ
Preparation of [nPr2P(S)](Me3Si)C؍CH2 (10): To a cold (Ϫ78 °C)
solution of (Me3Si)2CHPCl2 (3.07 g, 11.76 mmol) in diethyl ether
(100 mL) was added, dropwise, a solution of nPrMgCl in diethyl
ether (11.76 mL, 23.52 mmol). The solution was allowed to attain
˚
organic phase was dried with activated 4-A molecular sieves and
solvent was removed in vacuo to give the diphosphane
(Ph2P)(Me2P)CH2 as a colorless oil.
Eur. J. Org. Chem. 2004, 1043Ϫ1048
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1047

K. Izod, W. McFarlane, B. V. Tyson
FULL PAPER
To a solution of the diphosphane (Ph2P)(Me2P)CH2 (4.74 g,
18.20 mmol) in dichloromethane (40 mL) was added elemental sul-
fur (1.17 g, 36.40 mmol) and this mixture was stirred for 2 h. Sol-
vent was removed in vacuo and the white solid was dissolved in
THF (20 mL), treated with nBuLi (6.76 mL, 16.56 mmol) and left
to stir for 12 h. The resulting deep orange solution was added,
dropwise, to a cold (Ϫ78 °C) solution of chlorotrimethylsilane
(2.10 mL, 16.56 mmol) in diethyl ether (10 mL). The solution was
allowed to attain room temperature and was treated with a further
equivalent of nBuLi (6.76 mL, 16.56 mmol) and stirred overnight.
To the resulting solution was added paraformaldehyde (2.49 g,
82.8 mmol) and diethyl ether (20 mL) and the mixture was stirred
for 1 h before deoxygenated water (30 mL) was added. The organic
layer was decanted, the aqueous layer was extracted into diethyl
ether (3 ϫ 10 mL) and the combined organic extracts were dried
Acknowledgments
The authors gratefully acknowledge the support of the EPSRC and
the Royal Society.
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[4]
˚
with activated 4-A molecular sieves. The dried solution was filtered
[5]
and solvent was removed in vacuo to give a colorless oil which
yielded 12 as a white crystalline solid on the addition of warm light
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2
δ ϭ 1.89 (d, JPH ϭ 13 Hz, CH3), 6.02 (m,1 H, ϭCH2), 7.41Ϫ7.84
(m, 11 H, Ph and ϭCH2) ppm. 13C{1H} NMR (CDCl3, 25 °C):
δ ϭ 23.55 (CH3), 128.8, 130.3, 131.9 (Ph), 147.8 (ϭCH2) ppm.
31P{1H} NMR (CDCl3, 25 °C): δ ϭ 42.7 (d, JP,P ϭ 30 Hz, PPh2),
43.0 (d, JP,P ϭ 30 Hz, PMe2) ppm.
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Reaction between [(nPr2P)(Me3Si)2C]Li and Paraformaldehyde: To
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3.87 mmol) in light petroleum (20 mL) was added tBuLi (6.58 mL,
3.87 mmol) and this mixture was stirred for 12 h. To the resulting
solution was added THF (10 mL) and solid paraformaldehyde
(1.00 g, 33.30 mmol). This mixture was stirred for 1 h and then de-
gassed water (20 mL) was added. The organic layer was decanted
and the aqueous phase was extracted into diethyl ether (3 ϫ
10 mL). The combined organic extracts were dried with activated
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˚
4-A molecular sieves and then solvent was removed in vacuo to
give a pale yellow oil. Flash distillation of this oil under reduced
pressure (20 °C, 10Ϫ2 Torr) gave 5 as a colorless oil. Spectroscopic
data for 5: 1H NMR (CDCl3, 24 °C): δ ϭ 1.10Ϫ1.45 (m, 14 H,
nPr), 5.59 (m, 1 H, ϭCH2), 5.65 (m, 1 H, CHϭ), 6.14 (m, 1 H, ϭ
CH2) ppm. 31P{1H} NMR (CDCl3, 24 °C): δ ϭ Ϫ28.0 ppm. EIMS
(of the sulfide): m/z ϭ 176.0795 [C8H17PS: 176.0789].
[15]
[16]
[17]
Received October 28, 2003
1048
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 1043Ϫ1048