Chemical behaviour of a prototype boryl(phosphino)carbene

Article abstract of DOI:10.1002/chem.201303039

We recently disclosed the synthesis of a novel push-pull boryl(phosphino)carbene. To determine the influence of this substitution pattern on the chemical behaviour, a study into the reactivity of the prototype (1) of this new family of B(sp²)-substituted phosphinocarbenes was undertaken. Carbene 1 exhibits one of the most common intramolecular rearrangements of singlet carbenes, involving a 1,2-mesityl shift, and typical [2+1] cycloaddition reactions with electron-poor acrylonitrile. A pronounced α,β-ambiphilic character was also shown by the reaction of 1 with benzaldehyde, leading to phosphorylalkene 4. Due to its specific electronic properties, carbene 1 also exhibits unprecedented reactivity with chloroacrylonitrile, enabling the formation of bicyclo[1.1.0]phosphetanium salt 6 and borylcyclopropene 9, which have been fully characterised by NMR spectroscopy and X-ray crystallography. The reactivity of stable boryl(phosphino)carbene 1 has been investigated. It showed the typical reactivity of transient singlet carbenes (1,2-migration and [2+1] cycloaddition), together with marked α,β-ambiphilic character (see scheme). Due to its specific electronic properties, carbene 1 enabled the formation of an original bicyclo[1.1.0]phosphetanium salt and a borylcyclopropene. Copyright

Full text of DOI:10.1002/chem.201303039

DOI: 10.1002/chem.201303039
Full Paper
&
Carbene Chemistry
Chemical Behaviour of a Prototype Boryl(phosphino)carbene
Florie Lavigne,[a] Eddy Maerten,*[a] Gilles Alcaraz,[b] Nathalie Saffon-Merceron,[c] and
Antoine Baceiredo*[a]
Abstract: We recently disclosed the synthesis of a novel
“push–pull” boryl(phosphino)carbene. To determine the in-
fluence of this substitution pattern on the chemical behav-
iour, a study into the reactivity of the prototype (1) of this
new family of B(sp2)-substituted phosphinocarbenes was un-
dertaken. Carbene 1 exhibits one of the most common intra-
molecular rearrangements of singlet carbenes, involving
a 1,2-mesityl shift, and typical [2+1] cycloaddition reactions
with electron-poor acrylonitrile. A pronounced a,b-ambiphil-
ic character was also shown by the reaction of 1 with ben-
zaldehyde, leading to phosphorylalkene 4. Due to its specific
electronic properties, carbene 1 also exhibits unprecedented
reactivity with chloroacrylonitrile, enabling the formation of
bicyclo[1.1.0]phosphetanium salt 6 and borylcyclopropene 9,
which have been fully characterised by NMR spectroscopy
and X-ray crystallography.
Introduction
stabilisation mode, leading to “push–push”, “push–spectator”
or “push–pull” carbenes. While aminocarbenes are predomi-
nantly push–push[2] or push–spectator[6] stabilised, the push–
pull mode is restricted to a limited number of phosphinocar-
benes featuring an additional p-accepting group, which in-
clude silyl,[1] phosphonio[7] or 2,6-bis(trifluoromethyl)phenyl
groups.[8] As a part of our research program aiming at extend-
ing this class of carbenes, we recently disclosed the synthesis
of a prototype (1) of the push–pull boryl(phosphino)carbene
family by deprotonation of the parent borylated methylene-
phosphonium salt (Figure 1).[9] With the presence of a B(sp2)-
containing boryl group adjacent to the carbenic centre in 1,
one could expect to induce a stabilising push–pull effect of
greater magnitude (Figure 1).
Carbenes represent an important family of compounds, de-
fined as neutral species featuring a divalent carbon atom with
only six electrons in the valence shell, that have long been
considered as transient intermediates. The isolation of a stable
phosphino(silyl)carbene in 1988[1] and of a crystalline imidazol-
2-ylidene compound in 1991,[2] in which two heteroatoms in-
teract with the carbene centre, made real breakthroughs in
this field. Since then, the chemistry of stabilised carbenes as
synthetic reagents, ligands or organo-catalysts has become
a very active area of investigation.[3] In this respect, the devel-
opment of various stabilisation modes by modifying the substi-
tution pattern at the carbon atom has been subject to detailed
study. To date, stable singlet carbenes are predominantly p sta-
bilised by the presence of at least one amino or phosphino
group at the carbenic centre.[4] The reduced energetic cost for
a nitrogen rather than a phosphorus atom to adopt a planar
geometry, favouring the p interaction of the lone pair of the
a-substituent with the pp orbital at the carbenic carbon atom,
renders amino groups significantly better p donors (or “push”)
than phosphino substituents.[5] In the case of stable non-cyclic
carbenes, the second substituent at the carbenic centre (sub-
stituted heteroatom, alkyl or aryl group) determines the overall
The reactivity of stabilised carbenes depends on the singlet–
triplet energy gap. With this in mind and because substituent
effects govern the energetic positions of the frontier ns and pp
[a] Dr. F. Lavigne, Dr. E. Maerten, Dr. A. Baceiredo
Universitꢀ de Toulouse, UPS, and CNRS
LHFA UMR 5069, 31062 Toulouse Cedex 9 (France)
Fax: (+33)561558204
E-mail: maerten@chimie.ups-tlse.fr
baceired@chimie.ups-tlse.fr
[b] Dr. G. Alcaraz
LCC, UPR CNRS 8241
31077 Toulouse (France)
[c] Dr. N. Saffon-Merceron
Universitꢀ de Toulouse, UPS, and CNRS
ICT FR 2599, 31062 Toulouse (France)
Figure 1. a) Push–push, push–spectator and push–pull stabilised carbenes.
b) Synthesis of boryl(phosphino)carbene 1.
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orbitals, a deeper investigation of the reactivity of boryl(phos-
phino)carbene 1 was undertaken. The aim is to better delin-
eate its synthetic potential, and continue to investigate its be-
haviour towards small molecules, such as CO2 and SO2.[10]
The more classical a,b-ambiphilic character resulting from
the Pp–Cp interaction in phosphinocarbenes is, however, re-
tained in compound 1. Indeed, carbene 1 quickly reacts with
a stoichiometric amount of water, quantitatively affording
compound 3 (Scheme 2). In the 31P{1H} NMR spectrum, the
Results and Discussion
The reactivity of phosphinocarbenes mirrors the degree of car-
bene perturbation, which is directly linked to the substitution
pattern at the carbenic centre; minor modifications of the elec-
tronic balance alter their stability. Push–pull phosphino-
(silyl)carbenes exhibit good thermal stability and drastic condi-
tions are often needed to observe intramolecular CÀH inser-
tion reactions into appropriately located side chains.[1] With
Scheme 2. Hydrolysis reaction of boryl(phosphino)carbene 1.
phosphorus atom of the phosphine oxide moiety resonates at
1
d=37.8 ppm.[15,16] In the H NMR spectrum, the two diastereo-
topic hydrogen atoms of the methylene group appear as a set
phosphino(aryl)carbenes, displaying
a similar stabilisation
2
of two doublets of doublets at d=2.31 (2JHH =13.8, JHP
=
mode, an intramolecular rearrangement through a 1,2-migra-
tion reaction is generally detected above approximately
808C,[11] which can also be induced at room temperature,
under photolytic conditions. Boryl(phosphino)carbene 1 is in
an intermediate situation since slow rearrangement into phos-
phaalkene 2, involving 1,2-migration of the phosphorus mesityl
group to the carbene centre, is observed at room temperature.
Monitoring the transformation by 31P NMR spectroscopy, in
THF, at 258C, indicates that the reaction reaches completion
after 24 h, whereas only 1 h is needed at 608C (Scheme 1). The
resulting phosphaalkene, 2, was isolated and fully character-
ised by multinuclear NMR spectroscopy. In the 31P{1H} NMR
spectrum, compound 2 displays a deshielded singlet at d=
231.7 ppm, falling in the expected range for a l2s3-P-contain-
ing species. In the 13C{1H} NMR spectrum, the carbon bound to
the phosphorus atom resonates at d=143.8 ppm, with a cou-
pling constant value (1JCP =61.2 Hz) indicative of direct connec-
tivity between these two atoms, as reported for phosphaal-
kenes.[12]
2
16.2 Hz) and 2.69 ppm (2JHH =13.8, JHP =22.2 Hz) in a 1:1 inte-
gration ratio.
The reactions between the phosphino(silyl)carbene and al-
dehydes have been investigated, and two competitive process-
es were observed. With aromatic aldehydes, the reaction pro-
ceeds through a concerted [2+1] cycloaddition reaction to
form a carbonyl group, leading to formation of oxiranes,[13]
whereas with alkyl aldehydes a competitive pathway was ob-
served through a [2+2]-like cycloaddition, providing a transient
oxaphosphetene that rapidly transforms into the correspond-
ing phosphorylated olefin.[17] The boryl(phosphino)carbene
1 reacts with benzaldehyde to produce exclusively the Z
isomer of boryl(phosphoxide)alkene 4 (Scheme 3).
As previously observed with carbon and sulfur dioxide,[10]
the olefinic derivative 4 could be rationalised by the formation
of an intermediate oxaphosphetene through a Wittig-type re-
action, illustrating the pronounced a,b-ambiphilic character of
carbene 1. Compound 4 was isolated and fully characterised
by multinuclear NMR spectroscopy. In the 31P{1H} NMR spec-
trum, a singlet is observed at d=44.6 ppm for the phosphine
oxide moiety. The 13C{1H} NMR spectrum exhibits, in addition
to the signals of the phenyl carbon atoms, a set of two dou-
blets at d=137.2 (1JCP =25.6 Hz) and 143.9 ppm (2JCP =2.4 Hz),
The absence of any reactivity with Lewis basic reagents, like
tert-butylisocyanide[13] or PMe3,[8,14] indicates poor electrophilic
behaviour of boryl(phosphino)carbene 1.
1
corresponding to the ethylenic carbon atoms. In the H NMR
Scheme 1. Thermal rearrangement of boryl(phosphino)carbene 1 into phos-
phaalkene 2.
Scheme 3. Reaction of boryl(phosphino)carbene 1 with benzaldehyde.
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spectrum, the presence of a doublet at d=7.40 ppm with
a large coupling constant value (3JPH =44.5 Hz) is in good
agreement with a vinylic proton in a trans position to the
phosphorus atom.
To get a more comprehensive view of the influence of the
boryl moiety on the carbenic character of this prototype bor-
yl(phosphino)carbene, we assessed the ability of 1 to undergo
cyclopropanation reactions with electron-deficient olefins.[3b] In
contrast to the case of phosphino(silyl)carbenes, carbene
1 does not react with styrene or methyl acrylate to give the
corresponding cyclopropanes. This is probably due to the
steric congestion around the carbene centre in 1. In addition,
the easy rearrangement of 1 into phosphaalkene 2 prevents
any thermal activation of the cycloaddition process. Neverthe-
less, carbene 1 smoothly reacts with chloroacrylonitrile in pen-
tane, at À308C (Scheme 4).
Figure 2. Molecular structure of 5 (syn-5 featuring the chlorine cis to the
phosphorus is represented here). Thermal ellipsoids were set at 50% proba-
bility. Hydrogen atoms were omitted for clarity; selected bond lengths [ꢁ]
and angles [8]: C33ÀC32 1.491(2), C1ÀCC33 1.522(2), C1ÀC32 1.536(2), P1ÀN1
1.691(1), P1ÀC2 1.862(2), P1ÀC1 1.892(2), B1ÀN2 1.402(2), B1ÀC17 1.593(2),
B1ÀC1 1.638(2); C32-C1-P1 117.45(11), C33-C1-C32 58.36(11), C32-C1-B1
117.05(13), N1-P1-C2 101.66(7), N1-P1-C1 111.52(7), C2-P1-C1 107.39(7), N2-
B1-C17 121.27(14), N2-B1-C1 122.54(14), C17-B1-C1 116.09(13).
ed for cyclopropylÀB(sp2) linkages (1.52–1.56 ꢁ),[19] probably for
steric reasons.
Interestingly, the presence of nucleophilic (P) and electro-
philic (CÀCl) centres, allows the easy formation of an original
bicyclic structure. Indeed, the addition of one equivalent of
silver triflate to a solution of 5 in CH2Cl2, at À808C, leads to
the formation of bicyclo[1.1.0]phosphetanium salt 6, as a mix-
ture of two isomers (67:33), characterised by two singlets at
d=15.7 and 7.6 ppm in the 31P{1H} NMR spectrum (Scheme 4).
The bicyclo[1.1.0]phosphetanium salt 6 can also be obtained
directly from the methylene phosphonium salt 7, which is the
precursor of carbene 1. In this case, deprotonation and cyclo-
propanation were performed in situ and stepwise, leading to
the direct formation of the bicyclic structure 6, which was iso-
lated, in 60% yield, as a mixture of two diastereomers in
a 55:45 ratio. Probably, the salts formed in the first step cata-
lyse the nucleophilic attack of the phosphine centre of the in
situ generated phosphino cyclopropane 5.
Scheme 4. Reaction of boryl(phosphino)carbene 1 with chloroacrylonitrile.
The resulting cyclopropane 5 was isolated in 55% yield. The
31P{1H} NMR spectrum displays a set of singlets at d=49.0 and
47.3 ppm, in a 77:23 integration ratio, indicative of the pres-
ence of two diastereomers. The observed diastereoselectivity
of the cyclopropanation process contrasts with the case of
phosphino(silyl)carbenes, which react diastereospecifically with
acrylates, leading to the exclusive formation of the syn iso-
mer.[13a,18] However, the selectivity observed with carbene 1 is
very similar to that obtained in the reaction of [2,6-bis(tri-
fluoromethyl)phenyl](phosphino)carbene with chloroacryloni-
trile.[11] The major isomer of 5 (dP =49.0 ppm) was analysed by
multinuclear NMR spectroscopy. In the 11B{1H} NMR spectrum,
1
a singlet is observed at d=43 ppm. The H NMR spectrum dis-
plays a multiplet at d=1.79 and a doublet of doublets at
Diastereoselective crystallisation of the mixture of the two
isomers of 6 from a saturated solution in toluene at À308C al-
lowed the full characterisation of the major diastereomer (dP =
15.7 ppm) and allowed us to deduce the spectroscopic data of
the minor one (dP =7.6 ppm). The 11B{1H} NMR spectrum of the
major diastereomer displays a signal at d=40 ppm. In the
1H NMR spectrum, two sets of signals are observed for the dia-
stereotopic hydrogen atoms of the methylene bridge: dou-
blets of doublets at d=3.11 (2JHH =5.2, 3JHP =27.6 Hz) and
3
2.38 ppm (2JHH =3.3, JHP =6.0 Hz) in a 1:1 ratio for the diaste-
reotopic protons of the methylene group. The 13C{1H} NMR
spectrum exhibits a set of doublets at d=39.2 (1JCP =7.5 Hz)
and 29.7 ppm (2JCP =5.5 Hz), corresponding to the PCB and
methylenic carbon atoms, respectively. The X-ray structure of 5
was determined at À808C, revealing the presence of two dia-
stereoisomers in the asymmetric unit, in
a 55:45 ratio
(Figure 2). The P1ÀC1 bond length (1.892(2) ꢁ) is in agreement
with that reported for PÀC single bonds in phosphinocyclopro-
panes.[11,18a] The B1ÀC1 bond is slightly longer than that report-
3
2.99 ppm (2JHH =5.2, JHP =53.7 Hz). The solid-state structure of
the major diastereomer of 6 was determined by a single-crystal
Chem. Eur. J. 2014, 20, 297 – 303
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Scheme 5. Reaction of bicyclo[1.1.0]phosphetanium salt 6 with KF.
temperature into phosphaalkene 2 by a 1,2-mesityl migration
to the carbenic centre. This boryl(phosphino)carbene (1) pres-
ents an important a,b-ambiphilic character, reacting with ben-
zaldehyde and leading to the corresponding boryl(phosphox-
ide) alkene 4, rather than the boryl(phosphino)oxirane. In addi-
tion, the absence of any reactivity towards Lewis bases indi-
cates that 1 is weakly electrophilic. In contrast, it readily reacts
with the electron-poor chloroacrylonitrile to give the corre-
sponding [2+1] cycloadduct. The resulting boryl(phosphino)cy-
clopropane 5 displays interesting intramolecular reactivity, and
can be converted into the bicyclo[1.1.0]phosphetanium salt 6,
featuring an original structure with two fused three-membered
rings. The formal extrusion of a phosphenium fragment from
the bicyclic structure 6 allows easy synthesis of borylcyclopro-
pene 9 under mild conditions.
Figure 3. Molecular structure of 6. Thermal ellipsoids were set at 50% proba-
bility. Hydrogen atoms, GaCl4 and solvent were omitted for clarity; selected
À
bond lengths [ꢁ] and angles [8]: P1ÀN1 1.625(3), P1ÀC1 1.770(3), P1ÀC3
1.784(3), P1ÀC11 1.786(3), N2ÀB1 1.391(4), N3ÀC4 1.147(5), C3ÀC4 1.434(5),
B1ÀC1 1.605(5), C1ÀC2 1.540(5), C1ÀC3 1.614(4), C2ÀC3 1.484(4), B1ÀC26
1.588(5); N1-P1-C1 117.94(14), N1-P1-C3 128.46(15), C1-P1-C3 54.02(14), N1-
P1-C11 113.99(14), C1-P1-C11 119.53(15), C3-P1-C11 110.51(15), N2-B1-C26
123.5(3), N2-B1-C1 119.7(3), C2-C3-C1 59.4(2), C2-C3-P1 99.8(2), C1-C3-P1
62.55(16), C26-B1-C1 116.6(3), C2-C1-B1 120.0(3), C2-C1-C3 56.1(2), B1-C1-C3
131.0(3), C2-C1-P1 98.2(2).
X-ray diffraction analysis at À808C, clearly showing the tetrava-
lent environment of the phosphorus centre, and the bicyclic
structure (Figure 3).
In conclusion, due to its unique electronic properties, the
push–pull boryl(phosphino)carbene 1 exhibits both classical
and unprecedented reactivities. Our efforts to develop new
push–pull models are still underway and will allow a better un-
derstanding of this type of reactivity.
The intracyclic PÀC bond lengths (1.770(3) and 1.784(3) ꢁ)
are shorter than those of classical PÀC single bonds (1.80–
1.90 ꢁ) and lie between the bond lengths of phosphetanium
salts (PÀCꢀ1.800 ꢁ)[20] and those of phosphiranium cations
(PÀCꢀ1.760 ꢁ).[21] A similar trend is observed for the variation
of the C1-P1-C3 bond angle (54.02(14)8), which also lies be-
tween that in phosphetanium (75–828) and phosphiranium
salts (47–528).[20,21]
By analogy with the reactivity of phosphiranium salts, the
ability of 6 to undergo the cheletropic extrusion of a phosphe-
nium fragment was evaluated.[22] In the presence of diphenyla-
cetylene or dimethyl acetylenedicarboxylate, no reaction was
observed, even at an elevated temperature. In contrast, the ad-
dition of one equivalent of potassium fluoride to 6 led quanti-
tatively to borylcyclopropene 9 and fluorophosphine 8, which
were fully characterised spectroscopically. In this case, instead
of generating a transient phosphenium salt, the reaction prob-
ably involves the transient formation of a bicyclic phosphorane
(Scheme 5).[23]
Experimental Section
General procedures: All manipulations were performed under an
inert atmosphere of argon by using standard Schlenk techniques.
1
Dry and oxygen-free solvents were used. H, 11B, 13C and 31P NMR
spectra were recorded on Brucker Avance 400 or Avance 300 spec-
1
trometers. H and 13C NMR chemical shifts are reported in parts per
million (ppm) relative to Me4Si as an external standard. 31P and
11B NMR downfield chemical shifts are expressed in ppm relative to
85% H3PO4 and BF3·Et2O, respectively. IR spectra were recorded on
a Varian 640-IR spectrophotometer. Mass spectra were recorded on
a Hewlett Packard 5989A spectrometer. Carbene 1 and methylene-
phosphonium 7 were prepared according to a literature proce-
dure.[9]
Phosphaalkene 2: Phosphaalkene 2 was obtained quantitatively
by heating a solution of carbene 1 (72 mg, 0.15 mmol) in [D8]THF
(1 mL) at reflux for 1 h or by stirring the solution at room tempera-
ture for 24 h. The product was spectroscopically characterised
without further purification. 1H NMR (400 MHz, [D8]THF): d=0.80
(d, 3JHH =6.3 Hz, 12H; PNCHCH3), 0.85 (d, 3JHH =6.9 Hz, 6H;
BNCHCH3), 1.09 (d, 3JHH =6.9 Hz, 6H; BNCHCH3), 1.76 (m, 6H;
CH3orthoB), 1.82 (m, 3H; CH3paraB), 1.97 (s, 6H; CH3orthoMes), 1.98 (s,
3H; CH3paraMes), 3.22 (septd, 3JHH =6.9, 3JPH =13.5 Hz, 2H;
PNCHCH3), 3.32 (sept, 3JHH =7.2 Hz, 2H; BNCHCH3), 6.32 (s, 2H;
CHArMes), 6.46 ppm (s, 2H; CHArB); 13C{1H} NMR (100 MHz, [D8]THF):
d=19.9 (s; CH3orthoMes), 20.2 (s; CH3paraMes), 21.3 (s; CH3orthoB), 22.0
Conclusion
The chemical behaviour of the novel push–pull boryl(phosphi-
no)carbene 1 was thoroughly evaluated through a range of ap-
propriate reactions mirroring the different aspects generally
encountered in stabilised carbenes. We have shown that car-
bene 1 is relatively stable but not to the same degree as
phosphino(silyl)carbenes. Indeed, it slowly rearranges at room
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(s; CH3paraB), 22.9 (s; BNCHCH3), 23.0 (s; PNCHCH3), 23.5 (s;
BNCHCH3), 47.1 (s; BNCHCH3), 48.1 (d, 3JCP =3.1 Hz; PNCHCH3),
129.7 (s; CHArB), 130.7 (d, 4JCP =1.4 Hz; CHArPh), 135.3 (s; CorthoB),
1
4
137.2 (d, JCP =25.6 Hz; PCB), 138.8 (d, JCP =2.6 Hz; CparaP), 138.9 (s;
CparaB), 140.4 (s; CorthoB), 140.9 (d, 2JCP =12.4 Hz; CorthoP), 143.8 (s;
CorthoP), 143.9 ppm (d, 2JCP =2.4 Hz; PC=CH); the carbon ipso to
boron was not observed; 31P{1H} NMR (121.5 MHz, CDCl3): d=
44.6 ppm (s); 11B{1H} NMR (96.3 MHz, CDCl3): d=45.1 ppm (s);
HRMS (ESI+): m/z calcd for C38H56BN2OP: 621.4121 [M+Na]+;
found: 621.4132.
126.3 (s; CHArMes), 127.4 (s; CHArB), 133.3 (s; CorthoMes), 135.0 (s;
1
CorthoB), 139.1 (s; CparaB), 140.1 (s; CparaMes), 143.8 ppm (d, JCP
=
61.2 Hz; PCB); 31P{1H} NMR (162 MHz, [D8]THF): d=231.7 ppm;
11B{1H} NMR (128 MHz, [D8]THF): d=42.6 ppm; HRMS (ESI+): m/z
calcd for C31H50BN2P: 493.3883 [M+H]+; found: 493.3872.
Phosphine oxide 3: At room temperature, water (2.5 mL,
0.14 mmol) was added to a solution of boryl(phosphino)carbene
1 (70 mg, 0.14 mmol) in pentane (2 mL). Within 5 min, the solution
becomes cloudy. The precipitate was purified and filtered through
a small layer of silica gel (eluent: ethanol). A yellow powder was
obtained (44 mg, 62% yield). M.p.=151–1528C; 1H NMR
Cyclopropane syn-and anti-5: 2-Chloroacrylonitrile (3 equiv,
48.7 mL, 0.60 mmol) was slowly added to a solution of carbene
1 (100 mg, 0.20 mmol) in pentane (1.5 mL) at À808C. The solution
was warmed to À308C, stirred at this temperature for 24 h, filtered
and the solvent was removed under vacuum. Extraction with pen-
tane (2ꢂ5 mL) was performed and cyclopropane 5 was purified by
silica gel chromatography with pentane as the eluent. A mixture of
two diastereoisomers was obtained in a 77:23 ratio, as indicated by
31P NMR spectroscopy (64 mg, 55% yield). White crystals of 5 in
a 55:45 ratio of isomers (estimated by 31P NMR analysis) could be
obtained from a saturated solution in pentane at À408C. IR (THF):
3
(300.1 MHz, C6D6): d=0.79 (d, JHH =6.9 Hz, 3H; BNCHCH3), 0.84 (d,
3JHH =6.6 Hz, 3H; BNCHCH3), 1.04 (d,3JHH =6.6 Hz, 6H; PNCHCH3),
1.30 (d, 3JHH =6.9 Hz, 6H; PNCHCH3), 1.36 (d, 3JHH =7.2 Hz, 3H;
BNCHCH3), 1.52 (d, 3JHH =6.9 Hz, 3H; BNCHCH3), 2.03 (s, 3H;
CH3orthoP), 2.15 (s, 3H; CH3orthoB), 2.18 (s, 3H; CH3orthoB), 2.24 (s, 3H;
CH3paraB), 2.31 (dd, 2JHH =14.1, 2JHP =16.2 Hz, 1H; PCH2B), 2.37 (s,
u˜ =2305 cmÀ1
.
2
2
3H; CH3paraP), 2.68 (dd, JHH =14.1, JHP =22.8 Hz, 1H; PCH2B), 2.88
(s, 3H; CH3orthoP), 3.25 (sept, 3JHH =7.5 Hz, 1H; BNCHCH3), 3.42
(sept, 3JHH =6.9 Hz, 2H; PNCHCH3), 3.60 (sept, 3JHH =6.9 Hz, 1H;
BNCHCH3), 6.44 (s, 1H; CHArP), 6.50 (s, 1H; CHArB), 6.59 (s, 1H;
CHArB), 6.64 ppm (s, 1H; CHArP); 13C{1H} NMR (75.1 MHz, C6D6): d=
20.9 (s; CH3orthoP), 21.2 (s; CH3orthoB), 22.0 (s; BNCHCH3), 22.1 (s;
BNCHCH3), 22.6 (s; CH3orthoB), 22.9 (s; CH3paraP), 23.2 (s; CH3paraB),
23.2 (d, 3JCP =2.2 Hz; PNCHCH3), 23.6 (d, 3JCP =2.8 Hz; PNCHCH3),
24.4 (s; CH3orthoP), 24.9 (s; BNCHCH3), 25.0 (s; BNCHCH3), 28.6 (d,
1JCP =82.5 Hz; PCH2B), 47.4 (d, 2JCP =3.1 Hz; PNCHCH3), 48.5 (s;
BNCHCH3), 50.4 (s; BNCHCH3), 127.3 (s; CHArB), 127.4 (s; CHArB),
Major diastereomer: 1H NMR (300.1 MHz, C6D6): d=0.31 (m, 3H;
3
BNCHCH3), 1.00 (d, 3JHH =6.9 Hz, 3H; BNCHCH3), 1.01 (d, JHH
=
3
6.9 Hz, 3H; BNCHCH3), 1.09 (d, JHH =7.2 Hz, 3H; PNCHCH3), 1.18 (d,
3JHH =7.2 Hz, 3H; PNCHCH3), 1.26 (s, 3H; CH3orthoB), 1.46 (m, 3H;
BNCHCH3), 1.69 (d, 3JHH =6.6 Hz, 3H; PNCHCH3), 1.74 (s, 3H;
CH3orthoP), 1.78 (d, 3JHH =7.2 Hz, 3H; PNCHCH3), 1.79 (m, 1H;
2
CH2cycle), 2.08 (s, 3H; CH3paraP), 2.13 (s, 3H; CH3paraB), 2.38 (dd, JHH
=
=
3
4
3.3, JHP =6.0 Hz, 1H; CH2cycle), 2.45 (s, 3H; CH3orthoB), 2.81 (d, JHP
3.6 Hz, 3H; CH3orthoP), 3.13 (m, 1H; BNCHCH3), 3.61 (m, 1H;
BNCHCH3), 3.82 (sept, 3JHH =7.2 Hz, 1H; PNCHCH3), 5.19 (septd,
3
3JHH =6.6, JHP =2.7 Hz, 1H; PNCHCH3), 6.44 (s, 1H; CHArB), 6.54 (m,
1
3
128.9 (d, JCP =111.3 Hz; CipsoP), 130.4 (d, JCP =11.7 Hz; CHArP), 131.4
1H; CHArP), 6.69 (s, 1H CHArB), 6.76 ppm (d, 4JHP =6.3 Hz, 1H;
CHArP); 13C{1H} NMR (75.1 MHz, C6D6): d=20.4 (s; BNCHCH3), 20.8 (s;
CH3paraP), 21.0 (s; CH3paraB), 22.2 (s; CH3orthoB), 23.3 (m; CH3orthoP),
23.4 (s; PNCHCH3), 23.5 (s; PNCHCH3), 24.5 (s; CH3orthoP), 25.0 (s;
3
(d, JCP =12.9 Hz; CHArP), 135.5 (s; CorthoB), 137.7 (s; CparaB), 138.6 (s;
CorthoP), 139.5 (d, 4JCP =2.6 Hz; CparaP), 139.7 (s; CorthoB), 146.3 ppm
(d, 2JCP =10.1 Hz; CorthoP); the carbon ipso to boron was not ob-
served; 31P{1H} NMR (121.5 MHz, C6D6): d=37.8 ppm (s);
11B{1H} NMR (96.3 MHz, C6D6): d=43.4 ppm (s); HRMS (ESI+): m/z
calcd for C31H52BN2OP: 511.3989 [M+H]+; found; 511.3991.
BNCHCH3), 25.2 (s; CH3orthoB), 25.5 (s; BNCHCH3), 25.6 (s; PNCHCH3),
2
26.1 (s; BNCHCH3), 29.1 (d, 3JCP =8.9 Hz; PNCHCH3), 29.7 (d, JCP
=
1
5.5 Hz; CH2cycle), 39.2 (d, JCP =7.5 Hz; PCB), 50.1 (s; BNCHCH3), 51.8
(s; BNCHCH3), 52.0 (s; PNCHCH3), 52.3 (s; PNCHCH3), 119.9 (s; CN),
128.2 (s; CHArB), 128.3 (s; CHArB), 129.8 (d, 3JCP =7.7 Hz; CHArP),
Phosphorylalkene 4: At room temperature, benzaldehyde (58.2 mL,
0.57 mmol) was added to a solution of boryl(phosphino)carbene
1 (200 mg, 0.41 mmol) in pentane (3 mL). Within 5 min, the solu-
tion turned yellow. After evaporation of the solvent, the product
was purified by filtration through a small layer of silica gel (eluent:
131.9 (s; CHArP), 134.8 (d, 1JCP =21.9 Hz; CipsoP), 136.4 (s; CparaB),
2
138.5 (s; CorthoB), 138.8 (s; CparaP), 140.6 (s; Cortho B), 143.3 (d, JCP
=
3.3 Hz; CorthoP), 144.1 ppm (m; CorthoP); the bridgehead carbon atom
alpha to the nitrile was not observed; 31P{1H} NMR (121.5 MHz,
C6D6): d=49.0 ppm (s); 11B{1H} NMR (96.3 MHz, C6D6): d=42.6 ppm
(s).
Minor Diastereomer: 31P{1H} NMR (121.5 MHz, C6D6): d=47.3 ppm
(s).
diethyl ether). A yellow powder was obtained (150 mg 61% yield).
3
M.p.=120–1228C; 1H NMR (300.1 MHz, CDCl3): d=0.95 (d, JHH
=
3
6.0 Hz, 3H; BNCHCH3), 1.27 (d, JHH =6.9 Hz, 3H; PNCHCH3), 1.33 (d,
3JHH =6.9 Hz, 3H; PNCHCH3), 1.35 (d, 3JHH =7.5 Hz, 3H; PNCHCH3),
1.36 (d, 3JHH =7.0 Hz, 3H; BNCHCH3), 1.39 (d, 3JHH =6.5 Hz, 3H;
3
BNCHCH3), 1.59 (d, 3JHH =6.0 Hz, 3H; BNCHCH3), 1.67 (d, JHH
=
Bicyclo[1.1.0]phosphetanium salt 6: A solution of silver triflate
(57 mg, 0.22 mmol) in CH2Cl2 (1 mL) was added to a solution of cy-
clopropane 5 (130 mg, 0.22 mmol) in CH2Cl2 (2 mL) at À808C. The
solution was slowly warmed to room temperature (4 h) and fil-
tered. After removal of the solvent, crude compound 6 was
washed with pentane (3ꢂ3 mL). Compound 6 was obtained as
a white powder, containing two diastereoisomers in a ratio of
67:33 (85 mg, 55% yield). HRMS (ESI+): m/z calcd for C34H52BClN3P:
580.3759 [M+H]+; found: 580.3763; the counter-anion was found
to be chlorine by HRMS.
7.2 Hz, 3H; PNCHCH3), 1.89 (s, 3H; CH3orthoP), 2.00 (s, 3H; CH3paraB),
2.06 (s, 3H; CH3orthoB), 2.13 (s, 3H; CH3paraP), 2.22 (s, 3H; CH3orthoB),
2.80 (s, 3H; CH3orthoP), 3.39 (m, 1H; BNCHCH3), 3.65 (m, 1H;
BNCHCH3), 4.00 (sept, 3JHH =7.5 Hz, 1H; PNCHCH3), 4.33 (sept,
3JHH =7.0 Hz, 1H; PNCHCH3), 6.06 (s, 1H; CHArB), 6.07 (s, 1H; CHArP),
6.44 (s, 1H; CHArP), 6.69 (s, 1H; CHArB), 7.39 (m, 3H; CHArPh), 7.40
(d, 3JPH =44.5 Hz, 1H; PC=CHPh), 7.89 ppm (m, 2H; CHArPh);
13C{1H} NMR (75.1 MHz, CDCl3): d=20.8 (d, 5JCP =4.5 Hz; CH3paraP),
20.9 (s; CH3orthoB), 22.1 (s; BNCHCH3), 22.5 (s; PNCHCH3), 23.0 (s;
3
CH3orthoB), 23.1 (s; PNCHCH3), 23.3 (s; BNCHCH3), 23.9 (d, JCP
=
3
4.1 Hz; CH3orthoP), 24.0 (s; BNCHCH3), 24.1 (d, JCP =3.7 Hz; CH3orthoP),
25.0 (s; CH3paraB), 25.7 (s; PNCHCH3), 26.8 (s; BNCHCH3), 26.9 (s;
PNCHCH3), 46.6 (s; BNCHCH3), 48.4 (s; BNCHCH3), 51.3 (s;
PNCHCH3), 51.4 (s; PNCHCH3), 126.5 (s; CHArP), 127.1 (s; CHArP),
127.9 (s; CHArPh), 128.0 (d, 1JCP =111.4 Hz; CipsoP), 128.9 (s; CHArB),
Major diastereomer: 67% yield; IR (THF): u˜ =2150 cmÀ1 1H NMR
;
(400.1 MHz, CDCl3): d=1.15 (d, 3JHH =6.8 Hz, 3H; BNCHCH3), 1.21
(d, 3JHH =7.2 Hz, 3H; BNCHCH3), 1.22 (d, 3JHH =7.2 Hz, 6H;
PNCHCH3), 1.24 (s, 3H; CH3orthoB), 1.38 (d, 3JHH =6.8 Hz, 6H;
3
PNCHCH3), 1.51 (d, 3JHH =7.2 Hz, 3H; BNCHCH3), 1.52 (d, JHH
=
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6.8 Hz, 3H; BNCHCH3), 2.14 (s, 3H; CH3paraB), 2.28 (s, 3H; CH3orthoB),
2.44 (s, 3H; CH3paraP), 2.76 (s, 3H; CH3orthoP), 2.89 (s, 3H; CH3orthoP),
2.99 (dd, 2JHH =5.2, 3JHP =53.7 Hz, 1H; CH2cycle), 3.11 (dd, 2JHH =5.2,
3JHP =27.6 Hz, 1H; CH2cycle), 3.72 (septd, 3JHH =6.4, 3JHP =13.2 Hz,
was stirred for 48 h at room temperature to quantitatively afford
fluorophosphine 8 and borylcyclopropene 9.
Fluorophosphine 8: HRMS (ESI+): m/z calcd for C15H25NFP:270.1787
[M+H]+; found: 270.1756; 1H NMR (500.3 MHz, [D8]THF): d=1.01
3
2H; PNCHCH3), 3.77 (sept, JHH =6.8 Hz, 1H; BNCHCH3), 4.47 (sept,
3
4
(d, JHH =10.0 Hz, 12H; NCHCH3), 2.27 (s, 3H; CH3para), 2.44 (d, JHP
=
3JHH =7.2 Hz, 1H; BNCHCH3), 6.54 (s, 1H; CHArB), 6.73 (s, 1H; CHArB),
7.23 (d, 4JPH =6.4 Hz, 1H; CHArP), 7.24 ppm (d, 4JPH =6.0 Hz, 1H;
CHArP); 13C{1H} NMR (100.1 MHz, CDCl3): d=20.9 (s; CH3paraB), 21.6
(s; CH3paraP), 21.7 (s; BNCHCH3), 22.6 (s; CH3orthoB), 22.9 (s; CH3orthoP),
23.0 (s; PNCHCH3), 23.1 (s; PNCHCH3), 23.2 (s; BNCHCH3), 23.3 (s;
CH3orthoB), 24.0 (s; CH3orthoP), 24.7 (s; BNCHCH3), 25.6 (s; BNCHCH3),
2.5 Hz, 6H; CH3ortho), 2.91 (sept, 3JHH =5.0 Hz, 2H; NCHCH3),
6.86 ppm (d, 4JHH =1,6 Hz, 2H; CHAr); 13C{1H} NMR (125.8 MHz,
[D8]THF): d=20.0 (s; CH3para), 21.1 (s; CH3ortho), 22.7 (s; NCHCH3),
45.0 (s; NCHCH3), 129.9 (m; CHAr), 138.8 (s; Cpara), 140.7 ppm (d,
2JCP =21.3 Hz; Cortho); the ipso carbon could not be observed;
1
31P{1H} NMR (202.5 MHz, [D8]THF): d=151.2 ppm (d, JPF =984.2 Hz);
1
27.6 (d, JCP =48.5 Hz; PCB), 34.8 (d, 2JCP =2.2 Hz; CH2cycle), 50.5 (s;
1
19F NMR (282.4 MHz, [D8]THF): d=À113.8 ppm (d, JPF =984.2 Hz).
BNCHCH3), 52.9 (s; PNCHCH3), 54.0 (s; BNCHCH3), 110.8 (s; CN),
116.7 (d, 1JCP =125.4 Hz; CipsoP), 127.7 (s; CHArB), 127.9 (s; CHArB),
Borylcyclopropene 9: HRMS (ESI+): m/z calcd for C19H27BN2:
295.2346 [M+H]+; found: 295.2345; IR (THF): u˜ =2236 cmÀ1 (CN);
1H NMR (500.3 MHz, [D8]THF): d=1.16 (d, 3JHH =10.0 Hz, 6H;
3
3
130.6 (d, JCP =14.0 Hz; CHArP), 131.7 (d, JCP =13.6 Hz; CHArP), 137.5
2
(s; CorthoB), 138.4 (s; CparaB), 138.7 (s; CorthoB), 142.4 (d, JCP =12.3 Hz;
3
2
4
NCHCH3), 1.34 (d, JHH =10.0 Hz, 6H; NCHCH3), 1.50 (s, 2H; CH2cycle),
CorthoP), 143.6 (d, JCP =12.0 Hz; CorthoP), 148.4 ppm (d, JCP =2.6 Hz;
CparaP); the bridgehead carbon atom alpha to the nitrile was not
observed; 31P{1H} NMR (121.5 MHz, CDCl3): d=15.7 ppm (s);
11B{1H} NMR (128.4 MHz, CDCl3): d=40.4 ppm (s).
2.24 (s, 3H; CH3para), 2.29 (s, 6H; CH3ortho), 3.60 (m, 1H; NCHCH3),
3.74 (sept, 3JHH =10.0 Hz, 1H; NCHCH3), 6.78 ppm (s, 2H; CHAr);
13C{1H} NMR (125.8 MHz, [D8]THF): d=12.7 (s; CH2cycle), 20.2 (s;
CH3para), 20.7 (s; NCHCH3), 21.1 (s; CH3orho), 24.5 (m; NCHCH3), 45.3
(s; NCHCH3), 51.8 (s; NCHCH3), 96.2 (s; CCN), 112.1 (s; CN), 127.1 (s;
CHAr.), 136.8 (s; Cpara), 137.9 ppm (s; Cortho); the carbon ipso to boron
and the bridgehead carbon atom alpha to boron were not ob-
served; 11B{1H} NMR (160.5 MHz, [D8]THF): d=38.5 ppm (s).
Minor diastereomer: 33% yield; product not isolated; NMR spectra
were deduced from analysis of the mixture; 1H NMR (400.1 MHz,
3
CDCl3): d=1.13 (d, 3JHH =6.8 Hz, 3H; BNCHCH3), 1.17 (d, JHH
=
3
6.8 Hz, 3H; BNCHCH3), 1.38 (d, JHH =6.8 Hz, 6H; PNCHCH3), 1.39 (d,
3JHH =6.8 Hz, 6H; PNCHCH3), 1.42 (d, 3JHH =6.8 Hz, 3H; BNCHCH3),
1.50 (d, JHH =6.4 Hz, 3H; BNCHCH3), 2.21 (m, 2H; CH2cycle), 2.24 (s,
X-ray structural analysis: The data for the structures for 5 and 6
were collected on a Bruker-AXS Quazar APEX II diffractometer by
using a 30 W air-cooled microfocus source (ImS) with focusing mul-
tilayer optics (5) and on a Brucker-AXS SMART APEX II diffractome-
ter (6) at a temperature of 193(2) K, with MoKa radiation (wave-
length=0.71073 ꢁ) by using phi and omega scans. The details of
data collection and crystal structure refinements are summarised in
3
3H; CH3orthoB), 2.25 (s, 3H; CH3orthoB), 2.31 (s, 3H; CH3paraB), 2.38 (s,
3H; CH3orthoP), 2.39 (s, 3H; CH3paraP), 2.58 (s, 3H; CH3orthoP), 3.71 (m,
3
3
1H; BNCHCH3), 3.99 (septd, JHH =6.8, JHP =13.6 Hz, 2H; PNCHCH3),
3
4.38 (sept, JHH =6.8 Hz, 1H; BNCHCH3), 6.81 (s, 1H; CHArB), 6.84 (s,
1H; CHArB), 7.15 ppm (d, 4JPH =6.4 Hz, 2H; CHArP); 13C NMR
1
(100.1 MHz, CDCl3): d=6.9 (d, JCP =63.2 Hz; PCB), 21.0 (s; CH3orthoB),
2
21.6 (s; CH3paraP), 21.7 (s; CH3orthoP), 21.8 (s; BNCHCH3), 22.1 (d, JCP
=
13.1 Hz; CH2cycle), 22.6 (s; BNCHCH3), 23.6 (s; PNCHCH3), 23.8 (s;
CH3orthoB), 23.9 (s; CH3paraB), 24.0 (s; CH3orthoP), 24.1 (s; BNCHCH3),
24.2 (s; PNCHCH3), 24.3 (s; BNCHCH3), 49.8 (s; BNCHCH3), 51.8 (d,
Table 1. Crystal data and structure refinement for compounds 5 and 6.
5
6
1
2JCP =2.8 Hz; PNCHCH3), 53.7 (s; BNCHCH3), 106.9 (d, JCP =102.3 Hz;
empirical formula
formula weight
temperature [K]
wavelength [ꢁ]
crystal system
space group
a [ꢁ]
b [ꢁ]
c [ꢁ]
a [8]
b [8]
C34H52BClN3P
580.02
193(2)
0.71073
monoclinic
P21/c
11.0429(5)
34.2430(13)
9.6712(4)
90
110.854(2)
90
3417.5(2)
4
1.127
0.185
C48H68BCl4GaN3P
940.35
193(2)
0.71073
triclinic
CipsoP), 112.5 (s; CN), 128.0 (s; CHArB), 128.5 (s; CHArB), 130.6 (d,
3JCP =14.0 Hz; CHArP), 138.4 (s; CparaB), 138.7 (s; CorthoB), 139.0 (s;
CorthoB), 143.9 (d, 2JCP =13.7 Hz; CorthoP), 144.8 (d, 2JCP =9.9 Hz;
4
CorthoP), 148.9 ppm (d, JCP =2.8 Hz; CparaP); the bridgehead carbon
atom alpha to the nitrile was not observed; 31P{1H} NMR
(161.9 MHz, CDCl3): d=7.6 ppm (s); 11B{1H} NMR (128.4 MHz, CDCl3):
d=41.2 ppm (s).
¯
P1
11.3645(2)
12.5065(2)
20.1667(4)
75.4480(10)
88.6350(10)
67.2530(10)
2549.91(8)
2
Alternative procedure for synthesis of 6: Methylene phosphonium 7
(645 mg, 0.92 mmol) was dissolved in THF (6 mL). The solution was
cooled to À808C and a solution of potassium hexamethyldisilazide
(KHMDS, 275 mg, 1.38 mmol) in THF (2 mL) was added dropwise
(185 mg, 0.92 mmol). After 30 min at À808C, excess 2-chloroacrylo-
nitrile was added and then the solution was warmed to room tem-
perature and stirred overnight. A brown precipitate appeared. The
solvent was evaporated under vacuum and the crude product was
washed with pentane (4ꢂ5 mL). Compound 6 was isolated as
a light-brown powder (417 mg, 60% yield) in a 55:45 diastereoiso-
meric ratio (31P NMR). White crystals of the major isomer were ob-
tained, at À308C, from a saturated solution in toluene. Major dia-
stereomer: 55% yield; 31P{1H} NMR (121.5 MHz, CDCl3): d=
15.7 ppm (s). Minor diastereomer: 45% yield; 31P{1H} NMR
(121.5 MHz, CDCl3): d=7.6 ppm (s).
g [8]
volume [ꢁ3]
Z
1calcd [gcmÀ3
]
1.225
0.814
992
m (MoKa) [mmÀ1
F(000)
]
1256
crystal size [mm3]
reflections collected
independent reflections
Rint
0.10ꢂ0.10ꢂ0.08
38108
6881
0.40ꢂ0.20ꢂ0.08
33382
10215
0.0373
0.0458
max. and min. transmission
data/restraints/parameters
goodness-of-fit on F2
R1 [I>2s(I)]
0.9854 and 0.9818 0.9377 and 0.7365
6881/43/403
1.057
10215/397/648
1.050
0.0414
0.0568
wR2 [I>2s(I)]
0.1021
0.1434
R1 (all data)
wR2 (all data)
larg. diff. peak and hole [eꢁÀ3
0.0569
0.1099
0.231 and À0.228
0.0956
0.1631
0.498 and À0.391
Fluorophosphine 8 and borylcyclopropene 9: A solution of KF
(5 mg, 0.09 mmol) in [D8]THF (0.5 mL) was added to a solution of 6
(30 mg, 0.04 mmol, 67:33 mixture) in [D8]THF (0.6 mL). The solution
]
Chem. Eur. J. 2014, 20, 297 – 303
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ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
[10] F. Lavigne, E. Maerten, G. Alcaraz, V. Branchadell, N. Saffon-Merceron, A.
Baceiredo, Angew. Chem. 2012, 124, 2539; Angew. Chem. Int. Ed. 2012,
51, 2489.
[11] E. Despagnet-Ayoub, H. Gornitzka, D. Bourissou, G. Bertrand, Eur. J. Org.
Chem. 2003, 2039.
[12] K. Karaghiosoff, H. Klehr, A. Schmidpeter, Chem. Ber. 1986, 119, 410.
[13] a) A. Igau, A. Baceiredo, G. Trinquier, G. Bertrand, Angew. Chem. 1989,
101, 617; Angew. Chem. Int. Ed. Engl. 1989, 28, 621; b) G. Gilette, A. Igau,
A. Baceiredo, G. Bertrand, New J. Chem. 1991, 15, 393; c) O. Illa, A. Alvar-
ez-Larena, A. Baceiredo, V. Branchadell, R. M. OrtuÇo, Tetrahedron: Asym-
metry 2007, 18, 2617.
[14] S. Goumri-Magnet, O. Polishchuk, H. Gornitzka, C. J. Marsden, A. Baceire-
do, G. Bertrand, Angew. Chem. 1999, 111, 3938; Angew. Chem. Int. Ed.
Engl. 1999, 38, 3727.
Table 1. The data were integrated with SAINT and an empirical ab-
sorption correction with SADABS was applied.[24] The structures
were solved by direct methods using SHELXS-97[25] and refined by
using the least-squares method on F2.[25] All non-hydrogen atoms
were treated anisotropically. All hydrogen atoms attached to
carbon atoms were fixed geometrically and treated as riding on
their parent atoms with CÀH=0.95 (aromatic), 0.98 (CH3), 0.99
(CH2) or 1.0 ꢁ (CH) with Uiso(H)=1.2Ueq(CH, CH2) or Uiso(H)=
1.5Ueq(CH3). CCDC-951086 (5) and CCDC-951087 (6) contain the
supplementary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
[15] The carbenic centre presumably abstracts a proton from water, as was
predicted by theoretical calculations; however, nucleophilic attack of
OHÀ occurs at the oxophilic phosphorus moiety, leading, after 1,3-pro-
totropy, to phosphine oxide 3. For similar reactivity, see: J. D. Masuda,
D. Martin, C. Lyon-Saunier, A. Baceiredo, H. Gornitzka, B. Donnadieu, G.
Bertrand, Chem. Asian J. 2007, 2, 178. For calculations see: C.-S. Wu, M.-
D. Su, Dalton Trans. 2012, 41, 3253.
Acknowledgements
This work was supported by the CNRS and the Universitꢃ de
Toulouse, UPS.
[16] a) T. Kawashima, T. Ishii, N. Inamoto, Bull. Chem. Soc. Jpn. 1987, 60,
1831; b) O. Illa, X. Bagan, A. Baceiredo, V. Branchadell, R. M. OrtuÇo, Tet-
rahedron: Asymmetry 2008, 19, 2353.
[17] For similar Wittig-type reactions, see: a) O. Illa, H. Gornitzka, V. Brancha-
dell, A. Baceiredo, G. Bertrand, R. M. OrtuÇo, Eur. J. Org. Chem. 2003,
3147; b) O. Illa, H. Gornitzka, A. Baceiredo, G. Bertrand, V. Branchadell,
R. M. OrtuÇo, J. Org. Chem. 2003, 68, 7707.
Keywords: boron
cycloaddition · phosphiranium · Wittig reactions
·
borylcyclopropenes
·
carbenes
·
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