Convenient mild and selective hydrophosphination of functionalized alkenes: Access to P,O and P,S derivatives

Article abstract of DOI:10.1055/s-2008-1067275

The synthesis of new functionalized phosphines is carried out through the easy and atom economic hydrophosphination reaction of functionalized alkenes such as vinyl ethers and vinyl thioethers. The reactions occur under mild conditions without catalyst us

Full text of DOI:10.1055/s-2008-1067275

PAPER
3121
Convenient Mild and Selective Hydrophosphination of Functionalized
Alkenes: Access to P,O and P,S Derivatives
Uncatalyzed
H
yd
e
rophosphin
n
ation of
V
in
o
i
Thioe
t
Laboratoire de Chimie Moléculaire et Thio-organique, ENSICAEN, Université de Caen Basse-Normandie, CNRS,
6 boulevard du Maréchal Juin, 14050 Caen, France
Fax +33(2)31452877; E-mail: annie-claude.gaumont@ensicaen.fr
Received 2 May 2008; revised 20 June 2008
phine-boranes as hydrophosphinating agents. The com-
pounds obtained could be of great interest for
homogeneous catalysis as hemilabile ligands.8
Abstract: The synthesis of new functionalized phosphines is car-
ried out through the easy and atom economic hydrophosphination
reaction of functionalized alkenes such as vinyl ethers and vinyl
thioethers. The reactions occur under mild conditions without cata-
lyst using phosphine-boranes as hydrophosphinating agents.
The reaction conditions for the hydrophosphination of vi-
nyl ethers were set using the couple diphenylphosphine-
borane 1/ethyl vinyl ether (Equation 1). To prevent de-
complexation, the reaction was carried out using a low
amount of an inert solvent (toluene) at ambient tempera-
ture without any catalyst. To our delight, the whole pre-
cursor 1 was consumed after 24 hours leading to
phosphine-borane 2 as the main product (96%), the re-
maining percentage corresponding to the oxide of the de-
complexed hydrophosphination product. This preliminary
result shows that under these mild conditions, decomplex-
ation of the phosphine-borane by the ether is rather low. It
is also worth noting that no catalyst is required to promote
the reaction.
Key words: addition reactions, alkenes, boron, phosphorus, radical
reactions
Phosphines are important ligands in transition-metal-
catalyzed reactions.1 Among the variety of methods em-
ployed for their synthesis, hydrophosphination (i.e., the
addition of a P–H bond to an unsaturation) is a straightfor-
ward and efficient process, which fulfils the atom econo-
my principle. The main promoters used are metal
complexes, strong bases, acids, and free radicals.2 How-
ever, this approach continues to pose considerable chal-
lenges in the preparation of oxygen-sensitive phosphines.
An alternate approach using phosphine-boranes as hydro-
phosphinating agent has solved a number of difficulties.
Hence, the borane group acts as a protecting group and
prevents the oxidation of the phosphine. It also activates
through an inductive effect the P–H bond and consequent-
ly permits to perform the reactions under mild conditions
or even in the absence of a catalyst.3,4 Another advantage
of the phosphine-boranes is related to the existence of ef-
ficient methods to remove the borane.5 The hydrophos-
phination using phosphine-borane complexes has been
largely used with simple unsaturated derivatives.3 On the
other hand, little is known about the hydrophosphination
of functionalized derivatives3f,g,6 despite the fact that it
would give an easy entry to bifunctional phosphine
ligands. Here, we report the hydrophosphination of vinyl
ethers and vinyl thioethers, which are available substrates.
No precedent dealing with the hydrophosphination of
such substrates by phosphine-borane could be found in the
literature.2 The lack of examples may be related to the
Lewis base character of the oxygen or sulfur atom, which
could promote the decomplexation of the borane group
and thus deprotect the phosphine-borane leading to an un-
activated and unprotected phosphine.7 Herein, we docu-
ment for the first time results on the hydrophosphination
of vinyl ethers and vinyl thioethers using secondary phos-
BH3
r.t., 24 h
toluene
BH3
P
+
P
H
OEt
OEt
2
1
Equation 1
Only one regioisomer was detected by 31P NMR spectros-
1
copy. H NMR revealed the exclusive formation of the
anti-Markovnikov adduct 2. The observed regioselectivi-
ty is similar to that obtained under radical activationwith
free phosphines.9 However, in our system, only a slight
excess (1.2 equiv) of alkenes was used instead of the 2 or
3 equivalents, which are required in radical-activated pro-
cess. Moreover, the reaction requires neither thermal
activation nor UV irradiation, thus avoiding the polymer-
ization of the alkene. Finally, in contrast with ‘free’ phos-
phines, no workup was required. The adduct was easily
purified in air by flash filtration on a pad of silica gel
(flash chromatography using toluene as eluent) affording
2 in 76% yield. In the first trial, the reaction was carried
out on a 100 mg precursor scale but the reaction can easily
be scaled up to grams under the previously defined condi-
tions. In this case, a strong improvement of the isolated
yield is observed, indicating that the moderate yields,
which are obtained with low amount of precursors, are in-
herent to the purification process and not to the conditions
of the reaction.
SYNTHESIS 2008, No. 19, pp 3121–3125
x
x.
x
x
.
2
0
0
8
Advanced online publication: 05.09.2008
DOI: 10.1055/s-2008-1067275; Art ID: T07408SS
© Georg Thieme Verlag Stuttgart · New York

3122
B. Join et al.
PAPER
As shown in Table 1, the methodology can be successful- 48 hours affording phosphine-borane 7 in 64% yield after
ly applied to other acyclic and cyclic vinyl ethers. Butyl purification (Equation 2, Table 1, entry 6).
vinyl ether was totally hydrophosphinated in 24 hours
while 2-methoxypropene required 96 hours for a full con-
All the substrates being easily hydrophosphinated by 1
under mild conditions (r.t. or 35 °C), we then extended
version (Equation 2, Table 1, entries 2, 3). As in the pre-
our study to more electron-rich phosphine precursors,
vious example, no competing decomplexation of the
which are known to be less reactive than diarylphosphine
phosphine-borane was noticed. Tertiary phosphine-
derivatives.3 Methylphenylphosphine-borane 8 was first
selected. Addition of 8 to ethyl vinyl ether was performed
boranes 3 and 4 having a predictable regiochemistry (anti-
Markovnikov adducts) were isolated in 74 and 60%
at room temperature. The reaction was completed in 24
yields, respectively, and fully characterized. With 3,4-di-
hours and phosphine-borane 11 was isolated in 73% yield
(Equation 3, Table 2, entry 1).
hydro-2H-pyran, no strong influence of the cyclic struc-
ture on the reactivity was observed and hydro-
phosphination could be carried out in 48 hours at room
temperature. Regioselectively, the phosphorus atom en-
ters exclusively at the carbon in the b-position producing
as expected the phosphine-borane 5, which was isolated in
69% yield after flash chromatography (Equation 2,
Table 1, entry 4).
R2
R2
temp, time
toluene
BH3
BH3
P
P
+
R1
R1
OR3
H
OR3
8: R1 = Me, R2 = Ph
9: R1 = t-Bu, R2 = Ph
10: R1 = Cy, R2 = Cy
Equation 3
R3
BH3
temp, time
toluene
BH3
Table 2 Reaction of Phosphine-boranes 8–10 with Vinyl Ethers
R3
P
P
+
R2
H
XR1
Entry Precursor R3
Temp
(°C)
Time
Yield
(%)
Product
R2
XR1
1
1
2
3
4a
5
6
8
9
Et
r.t.
r.t.
70
75
r.t.
r.t.
24 h
7 d
73
11
12
13
13
13
14
Equation 2
Table 1 Reaction of 1 with Vinyl Ethers and Thioethers
Et
47
10
10
10
10
Bu
Bu
Bu
Et
48 h
30 min
96 h
96 h
22
Entry X
R1
R2
R3
Temp Time Yield Product
(°C)
(h)
24
24
96
48
(%)
76
74
60
69
14
1
2
3
4
O
O
O
Et
H
H
H
H
r.t.
2
3
4
5
54b
53b
Bu
Me
H
r.t.
a Microwave activation.
b Amount of Et3B used: 1.2 equiv.
Me
r.t.
r.t.
O
The reactivity of tert-butylphenylphosphine-borane 9
was, as expected, lower due to the steric bulkiness of the
tert-butyl group. Nevertheless, after seven days at room
temperature, hydrophosphination product 12 could be iso-
lated in a reasonable yield of 47% (Equation 3, Table 2,
entry 2). Finally, we selected dicyclohexylphosphine-
borane 10 as precursor. It soon became obvious that the
conditions defined for phosphines 2, 8, and 9 were inap-
propriate with such a bulky and electron-rich phosphine.
Hence after four days at room temperature, no hydrophos-
phination product was observed with ethyl vinyl ether.
Former studies on the hydrophosphination of alkenes with
such phosphine derivatives showed that the reaction re-
quired a thermal activation.3b,f Ethyl vinyl ether having a
low boiling point (bp 36 °C), we turned to butyl vinyl
ether, which was more adapted for a thermal activation
(bp 94 °C). Various temperatures were tested without suc-
cess. Only high temperature (70 °C, 48 h) afforded some
hydrophosphination product 13 although in a rather low
amount (36%), as determined by 31P NMR spectroscopy.
The expected product was accompanied by various side-
5
6
S
S
Et
H
H
H
H
35
35
24
48
69
64
6
7
Ph
P,S ligands have a different behavior than P,O ligands due
to the bulkiness of the sulfur atom and to its electronic
properties, which makes sulfur a softer ligand, according
to Pearson’s theory.10 We were consequently interested to
check our method in the synthesis of such P,S derivatives.
Ethyl vinyl sulfide was selected as a model substrate and
reacted with 1 under the previously defined conditions for
the oxygenated counterpart (24 h, r.t.). However, the con-
version remained low (58%). Upon slightly increasing the
temperature to 35 °C, an almost complete conversion was
obtained after 24 hours. Again, as with vinyl ethers, no de-
complexation of the phosphine borane was noticed and
only the anti-Markovnikov regioisomer was formed.11
Phosphine-borane 6 was isolated after purification in 69%
yield (Equation 2, Table 1, entry 5). With phenyl vinyl
sulfide, the hydrophosphination was complete at 35 °C in
Synthesis 2008, No. 19, 3121–3125 © Thieme Stuttgart · New York

PAPER
Uncatalyzed Hydrophosphination of Vinyl Ethers and Thioethers
3123
products and phosphine-oxides indicating decomplex- do not require any catalyst except for the very bulky and
ation of phosphine-borane derivatives. Nevertheless, electron-rich dicyclohexylphosphine-borane, where a rad-
phosphine 13 was isolated in 22% yield (Equation 3, ical activation using Et3B was applied at room tempera-
Table 2, entry 3). To improve the yield we used a micro- ture. Application in homogeneous catalysis of the
wave irradiation (MWI) device. Former studies had potential phosphine-ether ligands, which have been pre-
shown the compatibility of this device with phosphine- pared by this methodology, is under investigation.
boranes and its advantage with bulky and electron-rich
hydrophosphinating agents.3b,c,e,f However, the reaction
Phosphine-boranes 1,16 8,17 9,18 and 1019 were synthesized follow-
afforded mainly decomplexed and oxidized secondary
phosphines. The expected adduct 13 was isolated only in
low yield (14%) (Equation 3, Table 2, entry 4). These last
results show the importance of avoiding high temperature
in order to limit the decomplexation-oxidation of phos-
phine-boranes and the formation of side-products when
using ethers as substrates.12
ing published procedures. Toluene was dried by an Innovative
Technology Pure Solvent device. Solvents used for column chroma-
tography were directly used from commercial bottles. The micro-
wave irradiation apparatus was a Discover from CEM Company
with a maximal power of 300 watts.
1H, 13C, and 31P NMR spectra were recorded on Bruker DPX 250
and Bruker AC 400 spectrometers. 11B NMR spectra were recorded
on a Bruker AC 400 spectrometer. TMS was used as internal refer-
1
ence for recording the H and 13C NMR spectra. 85% H3PO4 and
Since thermal activation was inappropriate, our next study
focused on the use of a radical activator. This choice was
based on the fact that: i) we had previously proposed that
the mechanism of the uncatalyzed hydrophosphination re-
action using phosphine-borane derivatives could involve
a radical intermediate,3b,c and ii) a radical mechanism was
recently proposed for the addition of phosphate oxides to
alkenes in the presence of a catalytic amount of oxygen.13
To prevent the formation of side-products and the poly-
merization of the alkenes, we avoided AIBN, which re-
quires the use of a high temperature (65–70 °C) and
selected Et3B as a radical initiator. Trialkylboranes and
especially Et3B have been widely used as low temperature
initiators.14 To the best of our knowledge, they were never
employed with phosphine-borane derivatives although
they have been used in one report dealing with C–P bond
formation by hydrophosphination using hypophosphite as
hydrophosphinating agent.15 Et3B in hexane (1.2 equiv)
was simply added to the reaction mixture and the reaction
was run at room temperature using a 1:1.2 ratio of phos-
phine-borane 10/butyl vinyl ether in a small amount of
toluene. Under these conditions, the reaction was com-
plete in 96 hours at room temperature and compound 13
was isolated in 54% yield (Equation 3, Table 2, entry 5).
To verify that the reaction was indeed radical activated,
the experiment was repeated in the presence of a radical
trap (duroquinone). After 24 hours, secondary phosphine-
borane 10 was recovered unreacted and no trace of phos-
phine-borane 13 was detected by 31P NMR spectroscopy,
confirming the radical activation induced by Et3B. The re-
action was next carried out with ethyl vinyl ether in the
presence of Et3B, and 14 was isolated in 53% yield
(Equation 3, Table 2, entry 6). The Et3B activation was
also observed, although less impressive, in the reaction
between butyl vinyl ether and phosphine-borane 1, the re-
action being completed in 13 hours compared to 24 hours
in the absence of the radical catalyst. All these results are
in agreement with a radical-catalyzed process.
BF3·OEt2 were used as external reference for 31P and 11B NMR
spectroscopy, respectively. Coupling constants are reported in Hz.
Mass spectra were recorded on Varian MAT 311 and Varian Saturn
2000 spectrometers in high-resolution mode.
Uncatalyzed Hydrophosphination of Vinyl Derivatives;
General Procedure
An oven-dried Schlenk-tube was charged with phosphine-borane
precursor 1, 8 or 9 (1 equiv). After three cycles with oil pump
vacuum/N2 purge, the respective alkene (1.2 equiv) was added un-
der a N2 flow. Then, toluene (0.25 mL) was added to the solution.
The mixture was stirred for the time and at temperature indicated in
Tables 1 and 2 , and then cooled to r.t. as required. The crude prod-
uct was directly purified by silica gel chromatography. The pure
product was obtained after drying under vacuum.
Et3B-Catalyzed Hydrophosphination of Vinyl Derivatives with
10; General Procedure
An oven-dried Schlenk-tube was charged with phosphine-borane
precursor 10 (1 equiv). After three cycles with oil pump vacuum/N2
purge, the respective alkene (1.2 equiv) was added under a N2 flow.
Then, toluene (0.25 mL) and Et3B (1.2 equiv) were added to the so-
lution. The mixture was stirred for 96 h at r.t. The crude product was
directly purified by silica gel chromatography. The product was ob-
tained after drying under vacuum.
(2-Ethoxy)ethyldiphenylphosphine-borane (2)
Prepared from phosphine-borane 1 (100 mg, 0.5 mmol) and ethyl
vinyl ether (58 mL, 0.6 mmol); yield: 76%, translucent oil; Rf = 0.35
(toluene).
1H NMR (250 MHz, CDCl3): d = 7.75–7.72 (m, 1 H), 7.72–7.68 (m,
2 H), 7.68–7.64 (m, 1 H), 7.56–7.37 (m, 6 H), 3.65 (dt, 3JH,P = 15.2
3
3
Hz, JH,H = 7.5 Hz, 2H), 3.41 (q, JH,H = 7.0 Hz, 2 H), 2.60 (dt,
2JH,P = 11.4 Hz, JH,H = 7.5 Hz, 1 H), 2.55 (dt, JH,P = 11.4 Hz,
3
2
3JH,H = 7.5 Hz, 1 H), 1.096 (t, JH,H = 7.0 Hz, 3 H), 0.90 (qm,
3
1JH,B = 90.1 Hz, 3 H).
13C NMR (63 MHz, CDCl3): d = 132.1 (d, 2JC,P = 9.4 Hz), 131.2 (d,
4JC,P = 1.9 Hz), 129.3 (d, 1JC,P = 56.6 Hz), 128.8 (d, 3JC,P = 10.1 Hz),
66.3 (s), 64.9 (d, 2JC,P = 5.0 Hz), 26.4 (d, 1JC,P = 36.48 Hz), 15.0 (s).
31P NMR (101 MHz, CDCl3): d = 13.53 (dm, 1JP,B = 71.0 Hz).
HRMS: m/z calcd for [M – H]+.: 258.1174; found: 258.1182.
In summary, we have devised a fully regioselective hy-
drophosphination of functionalized alkenes, which gives
an efficient and easy access to a new family of ether and
thioether/phosphine-borane derivatives. All the reactions
were carried out under mild conditions (r.t. to 35 °C) and
(2-Butoxy)ethyldiphenylphosphine-borane (3)
Prepared from phosphine-borane 1 (100 mg, 0.5 mmol) and butyl
vinyl ether (78 mL, 0.6 mmol); yield: 74%; translucent oil; Rf = 0.2
(toluene).
Synthesis 2008, No. 19, 3121–3125 © Thieme Stuttgart · New York

3124
B. Join et al.
PAPER
1
1H NMR (250 MHz, CDCl3): d = 7.75–7.72 (m, 1 H), 7.72–7.68 (m,
2 H), 7.68–7.65 (m, 1 H), 7.54–7.39 (m, 6 H), 3.65 (dt, 3JH,P = 16.0
11B NMR (128 MHz, CDCl3): d = –37.15 (dq, JP,B = 65.2 Hz,
1JB,H = 81.4 Hz).
3
3
Hz, JH,H = 7.4 Hz), 6.43 (t, JH,H = 6.4 Hz, 2 H), 2.59 (dt,
HRMS: m/z calcd for [M–H]+.: 287.1195; found: 287.1182.
3
2
2JH,P = 11.5 Hz, JH,H = 7.4 Hz, 1 H), 2.55 (dt, JH,P = 11.5 Hz,
3JH,H = 7.4 Hz, 1 H), 1.52–1.36 (m, 2 H), 1.36–1.16 (m, 2 H), 0.86
(t, 3JH,H = 7.2 Hz, 3 H), 0.70–0.10 (m, 3 H).
(2-Mercaptophenyl)ethyldiphenylphosphine-borane (7)
Prepared from phosphine-borane 1 (100 mg, 0.5 mmol) and phenyl
vinyl sulfide (79 mL, 0.6 mmol); yield: 64%; translucent oil;
Rf = 0.7 (toluene).
1H NMR (250 MHz, CDCl3): d = 7.65–7.48 (m, 4 H), 7.48–7.27 (m,
6 H), 7.27–6.95 (m, 5 H), 3.02–2.89 (m, 2 H), 2.49–2.34 (m, 2 H),
0.92 (qm, 1JH,B = 82.5 Hz, 3 H).
13C NMR (63 MHz, CDCl3): d = 132.1 (d, 2JC,P = 9.4 Hz), 131.2 (d,
4JC,P = 2.5 Hz), 129.4 (d, 1JC,P = 56.0 Hz), 128.8 (d, 3JC,P = 10.1 Hz),
70.8 (s), 65.2 (d, 2JC,P = 5.0 Hz), 31.7 (s), 26.4 (d, 1JC,P = 36.5 Hz),
19.2 (s), 13.9 (s).
31P NMR (101 MHz, CDCl3): d = 13.72 (dm, 1JP,B = 72.0 Hz).
HRMS: m/z calcd for [M – BH3]+.: 286.1487; found: 286.1492.
13C NMR (63 MHz, CDCl3): d = 134.9 (s), 132.2 (d, 2JC,P = 9.4 Hz),
4
131.6 (d, JC,P = 2.5 Hz), 129.7 (s), 129.3 (s), 129.1 (s), 129.1 (d,
1
[(2-Methoxy)-2-methyl]ethyldiphenylphosphine-borane (4)
Prepared from phosphine-borane 1 (100 mg, 0.5 mmol) and 2-meth-
oxypropene (58 mL, 0.6 mmol); yield: 60%; translucent oil; Rf = 0.3
(toluene).
3JC,P = 10.1 Hz), 128.7 (d, JC,P = 55.3 Hz), 126.7 (s), 27.3 (d,
2JC,P = 2.5 Hz), 26.1 (d, 1JC,P = 32.1 Hz).
31P NMR (101 MHz, CDCl3): d = 16.20 (dm, 1JP,B = 67.0 Hz).
HRMS: m/z calcd for [M – BH3 + H]+.: 323.1023; found: 323.1022.
1H NMR (250 MHz, CDCl3): d = 7.79–7.64 (m, 4 H), 7.53–7.37 (m,
6 H), 3.84–3.67 (m, 1 H), 3.13 (s, 3 H), 2.67 (ddd, 2JH,H = 14.5 Hz,
(2-Ethoxy)ethylmethylphenylphosphine-borane (11)
Prepared from phosphine-borane 8 (70 mL, 0.5 mmol) and ethyl vi-
nyl ether (58 mL, 0.6 mmol); yield: 73%; translucent oil; Rf = 0.7
(CH2Cl2).
1H NMR (250 MHz, CDCl3): d = 7.82–7.66 (m, 2 H), 7.58–7.40 (m,
3 H), 3.78–3.62 (m, 1 H), 3.60–3.33 (m, 3 H), 2.29–2.05 (m, 2 H),
1.64 (d, 2JH,P = 10.5 Hz, 3 H), 1.14 (t, 3JH,H = 7.0 Hz, 3 H), 0.75 (qm,
1JH,B = 92.9 Hz, 3 H).
3
2
2JH,P = 13.3 Hz, JH,H = 7.3 Hz, 1 H), 2.24 (ddd, JH,H = 14.5 Hz,
3
3
2JH,P = 9.3 Hz, JH,H = 5.3 Hz, 1 H), 1.18 (dd, JH,H = 6.1 Hz,
4JH,P = 1.1 Hz, 3 H), 0.98 (qm, 1JH,B = 106.1 Hz, 3 H).
13C NMR (63 MHz, CDCl3): d = 132.5 (d, 2JC,P = 9.4 Hz), 132.2 (d,
4
2JC,P = 8.8 Hz), 131.2 (d, JC,P = 1.9 Hz), 131.1 (d, 4JC,P = 2.5 Hz),
1
1
130.5 (d, JC,P = 56.6 Hz), 130.0 (d, JC,P = 56.0 Hz), 128.9 (d,
3JC,P = 10.1 Hz), 128.7 (d, JC,P = 10.1 Hz), 73.0 (s), 56.0 (s), 33.9
3
(d, 1JC,P = 35.9 Hz), 20.9 (d, 3JC,P = 8.2 Hz).
13C NMR (63 MHz, CDCl3): d = 131.5 (d, 2JC,P = 9.4 Hz), 131.4 (d,
31P NMR (101 MHz, CDCl3): d = 14.43 (dm, 1JP,B = 70.7 Hz).
HRMS: m/z calcd for [M – H]+.: 271.1423; found: 271.1436.
4JC,P = 2.5 Hz), 129.9 (d, 1JC,P = 54.7 Hz), 128.9 (d, 3JC,P = 10.1 Hz),
1
66.4 (s), 65.2 (s), 28.3 (d, JC,P = 35.9 Hz), 15.2 (s), 11.7 (d,
1JC,P = 38.4 Hz).
Pyran-2-yldiphenylphosphine-borane (5)
31P NMR (101 MHz, CDCl3): d = 8.42 (qm, 1JP,B = 63.5 Hz).
HRMS: m/z calcd for [M – H]+.: 209.1267; found: 209.1267.
Prepared from phosphine-borane 1 (100 mg, 0.5 mmol) and 3,4-di-
hydro-2H-pyran (55 mL, 0.6 mmol); yield: 69%; translucent oil;
Rf = 0.3 (toluene).
tert-Butyl(2-ethoxy)ethylphenylphosphine-borane (12)
Prepared from phosphine-borane 9 (90 mL, 0.5 mmol) and ethyl vi-
nyl ether (58 mL, 0.6 mmol); yield: 47%; translucent oil; Rf = 0.3
(CH2Cl2).
1H NMR (250 MHz, CDCl3): d = 7.80–7.67 (m, 2 H), 7.57–7.40 (m,
3 H), 3.82–3.68 (m, 1 H), 3.53–3.30 (m, 1 H), 3.43 (t, 3JH,H = 7.1 Hz,
2 H), 2.59–2.39 (m, 1 H), 2.32–2.14 (m, 1 H), 1.14 (t, 3JHH = 7.1 Hz,
3 H), 1.11 (d, 3JH,P = 14.0 Hz, 9 H), 0.60 (qm, 1JH,B = 88.4 Hz, 3 H).
13C NMR (63 MHz, CDCl3): d = 133.4 (d, 2JC,P = 8.2 Hz), 131.4 (d,
4JC,P = 1.9 Hz), 128.5 (d, 3JC,P = 9.4 Hz), 125.9 (d, 1JC,P = 48.4 Hz),
66.4 (s), 65.5 (d, 2JC,P = 5.0 Hz), 29.2 (d, 1JC,P = 33.3 Hz), 25.4 (d,
2JC,P = 2.5 Hz), 19.9 (d, 1JC,P = 33.3 Hz).
1H NMR (250 MHz, CDCl3): d = 7.83–7.66 (m, 4 H), 7.57–7.40 (m,
5
6 H), 4.01–3.90 (m, 1 H), 3.90–3.79 (m, 1 H), 3.59 (dt, JH,P = 2.0
3
5
3
Hz, JH,H = 11.25 Hz, 1 H), 3.40 (dt, JH,P = 3.25 Hz, JH,H = 11.0
Hz, 1 H), 2.89–2.68 (m, 1 H), 1.87–1.54 (m, 4 H), 1.70–0.15 (m, 3
H).
13C NMR (63 MHz, CDCl3): d = 132.6 (d, 2JC,P = 8.8 Hz), 132.4 (d,
4
2JC,P = 8.8 Hz), 131.6 (d, JC,P = 2.5 Hz), 131.5 (d, 4JC,P = 2.5 Hz),
3
3
129.1 (d, JC,P = 9.4 Hz), 129.0 (d, JC,P = 9.4 Hz), 127.6 (d,
1JC,P = 54.7 Hz), 127.5 (d, JC,P = 54.1 Hz), 68.4 (s), 68.2 (d,
1
2JC,P = 8.7 Hz), 32.7 (d, 1JC,P = 34.3 Hz), 29.9 (s), 26.5 (d, 2JC,P = 9.9
Hz), 24.1 (s).
31P NMR (101 MHz, CDCl3): d = 16.63 (dm, 1JP,B = 61.5 Hz).
HRMS: m/z calcd for [M – H]+.: 283.1423; found: 283.1414.
31P NMR (101 MHz, CDCl3): d = 27.82 (qm, 1JP,B = 69.7 Hz).
Dicyclohexyl(2-butoxy)ethylphosphine-borane (13)
(2-Mercaptoethyl)ethyldiphenylphosphine-borane (6)
Prepared from phosphine-borane 1 (100 mg, 0.5 mmol) and ethyl
vinyl sulfide (61 mL, 0.6 mmol); yield: 69%; translucent oil;
Rf = 0.65 (toluene).
1H NMR (400 MHz, CDCl3): d = 7.75–7.62 (m, 4 H), 7.58–7.40 (m,
6 H), 2.72–2.64 (m, 2 H), 2.56 (q, 3JH,H = 7.4 Hz, 2 H), 2.55–2.47
(m, 2 H), 1.23 (t, 3JH,H = 7.4 Hz, 3 H), 1.02 (qm, 1JH,B = 81.4 Hz, 3
H).
13C NMR (63 MHz, CDCl3): d = 132.5 (d, 2JC,P = 8.8 Hz), 131.8 (d,
4JC,P = 2.5 Hz), 129.4 (d, 3JC,P = 9.5 Hz), 129.2 (d, 1JC,P = 54.8 Hz),
27.0 (d, 1JC,P = 32.7 Hz), 26.2 (s), 25.4 (d, 2JC,P = 2.0 Hz), 15.0 (s).
31P NMR (162 MHz, CDCl3): d = 15.34 (dm, 1JP,B = 65.2 Hz).
Prepared from phosphine-borane 10 (106 mg, 0.5 mmol), butyl vi-
nyl ether (78 mL, 0.6 mmol), and Et3B (600 mL, 1 mol·L–1 in hex-
ane); yield: 54%; translucent oil; Rf = 0.3 (toluene).
2
1H NMR (250 MHz, CDCl3): d = 3.62 (dt, JH,P = 15.3 Hz,
3JH,H = 7.7 Hz, 2 H), 3.42 (t, 3JH,H = 6.5 Hz, 2 H), 2.00–1.68 (m, 12
H), 1.68–1.48 (m, 4 H), 1.48–1.10 (m, 12 H), 0.91 (t, 3JHH = 7.3 Hz,
3 H), 1.00 to –0.30 (m, 3 H).
13C NMR (63 MHz, CDCl3): d = 70.8 (s), 65.9 (d, 2JC,P = 3.0 Hz),
31.9 (d, 1JC,P = 32.9 Hz), 31.8 (s), 27.0 (d, 3JC,P = 1.2 Hz), 26.9 (s),
26.8 (d, 2JC,P = 2.8 Hz), 26.7 (d, 2JC,P = 2.4 Hz), 26.0 (d, 3JC,P = 1.1
Hz), 19.8 (d, 1JC,P = 30.9 Hz), 19.4 (s), 13.9 (s).
31P NMR (101 MHz, CDCl3): d = 23.91 (dm, 1JP,B = 75.3 Hz).
HRMS: m/z calcd for [M – H]+.: 311.2675; found: 311.2677.
Synthesis 2008, No. 19, 3121–3125 © Thieme Stuttgart · New York

PAPER
Uncatalyzed Hydrophosphination of Vinyl Ethers and Thioethers
3125
Dicyclohexyl(2-ethoxy)ethylphosphine-borane (14)
(4) For examples of C–P coupling, see: (a)Julienne, D.; Lohier,
J.-F.; Delacroix, O.; Gaumont, A.-C. J. Org. Chem. 2007,
72, 2247. (b) Pican, S.; Gaumont, A.-C. Chem. Commun.
2005, 2393.
Prepared from phosphine-borane 10 (106 mg, 0.5 mmol), ethyl vi-
nyl ether (58 mL, 0.6 mmol), and Et3B (600 mL, 1 mol·L–1 in hex-
ane); yield: 53%; translucent oil; Rf = 0.3 (toluene).
(5) For reviews, see: (a) Gaumont, A.-C.; Carboni, B. In
Science of Synthesis, Vol. 6; Kaufmann, D. E.; Matesson, D.
S., Eds.; Thieme Verlag: Stuttgart, 2005, 485–512.
(b) Brunel, J.-M.; Faure, B.; Maffei, M. Coord. Chem. Rev.
1998, 178-180, 665. (c) Ohff, M.; Holz, J.; Quirmbach, M.;
Borner, A. Synthesis 1998, 1391.
3
1H NMR (250 MHz, CDCl3): d = 3.63 (dt, JH,P = 15.5 Hz,
3JH,H = 7.4 Hz, 2 H), 3.49 (q, 3JH,H = 7.0 Hz, 2 H), 1.98–1.62 (m, 13
H), 1.48–1.13 (m, 11 H), 1.20 (t, JH,H = 7.0 Hz, 3 H), 0.25 (qm,
3
1JH,B = 93.2 Hz, 3 H).
13C NMR (63 MHz, CDCl3): d = 66.2 (s), 65.7 (d, 2JC,P = 3.4 Hz),
31.9 (d, 1JC,P = 32.9 Hz), 26.9 (d, 3JC,P = 1.1 Hz), 26.8 (s), 26.7 (d,
2JC,P = 2.5 Hz), 26.6 (d, 2JC,P = 2.5 Hz), 25.9 (d, 3JC,P = 1.2 Hz), 19.8
(d, 1JC,P = 30.9 Hz), 15.2 (s).
31P NMR (101 MHz, CDCl3): d = 23.83 (dm, 1JP,B = 74.0 Hz).
HRMS: m/z calcd for [M – H]+.: 283.2362; found: 283.2367.
(6) Imamoto, T.; Oshiki, T.; Onozawa, T.; Kusumoto, T.; Sato,
K. J. Am. Chem. Soc. 1990, 112, 5244.
(7) Transfer of the borane group from a phosphorus to an
oxygen atom was already mentioned in the literature: see ref.
6.
(8) See, for example: (a) Lindner, E.; Wald, J.; Eichele, K.;
Fawzi, R. J. Organomet. Chem. 2000, 601, 220. (b) Valls,
E.; Suades, J. Organometallics 1999, 18, 5475. (c) Rogers,
C. W.; Wolf, M. O. Chem. Commun. 1999, 2297.
(9) (a) Lindner, E.; Schmid, M.; Wegner, P.; Nachtigal, C.;
Steinmann, M.; Fawzi, R. Inorg. Chim. Acta 1999, 296, 103.
(b) Dombek, B. D. J. Org. Chem. 1978, 43, 3408.
(10) Pearson, R. G. J. Am. Chem. Soc. 1963, 85, 3533.
(11) The anti-Markovnikov regioselectivity is similar to that
obtained under UV irradiation or AIBN activation with free
phosphines as reported by: Trofimov, B. A.; Gusarova, N.
K.; Malysheva, S. F.; Ivanova, N. I.; Sukhov, B. G.;
Belogorlova, N. A.; Kuimov, V. A. Synthesis 2002, 2207.
(12) With a simple alkene such as oct-1-ene, the hydrophos-
phination could be carried out at 80 °C without any
decomplexation and oxidative side reactions (see ref. 3b).
(13) Hirai, T.; Han, L.-B. Org. Lett. 2007, 9, 53.
(14) See, for example: (a) Miyabe, H.; Ueda, M.; Naito, T. Chem.
Commun. 2000, 2059. (b) Mase, N.; Watanabe, Y.; Toru, T.
Tetrahedron Lett. 1999, 40, 2797. (c) Nozaki, K.; Oshima,
K.; Utimoto, K. J. Am. Chem. Soc. 1987, 109, 2547.
(15) Deprele, S.; Montchamp, J.-L. J. Org. Chem. 2001, 66,
6745.
Acknowledgment
This work was performed within the ‘CRUNCH’ interregional net-
work. We gratefully acknowledge financial support from the
‘Ministère de la Recherche et des Nouvelles Technologies’, CNRS
(Centre National de la Recherche Scientifique), the ‘Région Basse-
Normandie’ and the European Union (FEDER funding) for financi-
al support.
References
(1) See, for example: van Leeuwen, P. W. N. M. Homogeneous
Catalysis, Understanding the Art; Kluwer Academic
Publishers: Dordrecht, 2004.
(2) For a recent review on hydrophosphination of alkene and
alkyne derivatives, see: Delacroix, O.; Gaumont, A.-C.
Curr. Org. Chem. 2005, 9, 1851.
(3) For examples of hydrophosphination with alkenes, see:
(a) Vallette, H.; Pican, S.; Boudou, C.; Levillain, J.;
Plaquevent, J.-C.; Gaumont, A.-C. Tetrahedron Lett. 2006,
47, 5191. (b) Mimeau, D.; Delacroix, O.; Join, B.; Gaumont,
A.-C. C. R. Chim. 2004, 7, 845. (c) Mimeau, D.; Delacroix,
O.; Gaumont, A.-C. Chem. Commun. 2003, 2928. For
examples with alkynes, see: (d) Join, B.; Mimeau, D.;
Delacroix, O.; Gaumont, A.-C. Chem. Commun. 2006,
3249. (e) Mimeau, D.; Gaumont, A.-C. J. Org. Chem. 2003,
68, 7016. For example with Michael acceptors, see:
(f) Join, B.; Delacroix, O.; Gaumont, A.-C. Synlett 2005,
1881. (g) Bourumeau, K.; Gaumont, A.-C.; Denis, J.-M.
Tetrahedron Lett. 1997, 38, 1923. For example with
carbonyles, see: (h) Bourumeau, K.; Gaumont, A.-C.; Denis,
J.-M. J. Organomet. Chem. 1997, 529, 205.
(16) Pellon, P. Tetrahedron Lett. 1992, 33, 4451.
(17) Lebel, H.; Morin, S.; Paquet, V. Org. Lett. 2003, 5, 2347.
(18) (a) Trippett, S.; Corfield, J. R.; De’ath, N. J. J. Chem. Soc. C
1971, 1930. (b) Harger, M. J. P. J. Chem. Soc., Perkin Trans.
1 1975, 514.
(19) Mohr, B.; Lynn, D. M.; Grubbs, R. H. Organometallics
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Synthesis 2008, No. 19, 3121–3125 © Thieme Stuttgart · New York