First examples of C-P cross-coupling reaction of vinyl tosylates with diphenylphosphine derivative: New access to vinylphosphine-boranes

Article abstract of DOI:10.1080/10426500802715551

Vinylphosphine-borane complexes are efficiently synthesized by palladium-catalyzed CP cross-coupling of vinyl tosylates with diphenylphosphine-borane. Both activated and unactivated vinyl tosylates are successfully used. The vinylphosphine derivatives are

Full text of DOI:10.1080/10426500802715551

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Phosphorus, Sulfur, and Silicon
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First Examples of C─P
Cross-Coupling Reaction
of Vinyl Tosylates with
Diphenylphosphine Derivative:
New Access to Vinylphosphine-
boranes
Delphine Julienne a , Olivier Delacroix a & Annie-
Claude Gaumont a
a Laboratoire de Chimie Moléculaire et
Thioorganique, UMR CNRS 6507, INC3M, FR 3038 ,
ENSICAEN & Université de Caen , Caen, France
Published online: 26 Mar 2009.
To cite this article: Delphine Julienne , Olivier Delacroix & Annie-Claude
Gaumont (2009) First Examples of C─P Cross-Coupling Reaction of Vinyl Tosylates
with Diphenylphosphine Derivative: New Access to Vinylphosphine-boranes,
Phosphorus, Sulfur, and Silicon and the Related Elements, 184:4, 846-856, DOI:
10.1080/10426500802715551
To link to this article: http://dx.doi.org/10.1080/10426500802715551
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Phosphorus, Sulfur, and Silicon, 184:846–856, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500802715551
First Examples of C P Cross-Coupling Reaction of Vinyl
Tosylates with Diphenylphosphine Derivative: New
Access to Vinylphosphine-boranes
Delphine Julienne, Olivier Delacroix,
and Annie-Claude Gaumont
Laboratoire de Chimie Mole´culaire et Thioorganique, UMR CNRS 6507,
INC3M, FR 3038, ENSICAEN & Universite´ de Caen, Caen, France
Vinylphosphine-borane complexes are efficiently synthesized by palladium-
catalyzed C P cross-coupling of vinyl tosylates with diphenylphosphine-borane.
Both activated and unactivated vinyl tosylates are successfully used. The vinylphos-
phine derivatives are purified by chromatography on silica gel.
Keywords C P cross-coupling reaction; phosphine-borane; vinylphosphine; vinyl tosy-
late
INTRODUCTION
The synthesis of vinylphosphines is of great interest for organic
chemists. They are important synthetic intermediates, especially for
the preparation of polyphosphines and ligands for organometallic
catalysis.1 For example, they can lead to new valuable bidentate
ligands after functionalization of the carbon–carbon double bond.
A survey of the literature reveals that only a few methods using
carbon–phosphorus (C P) bond formation have been developed to
access vinylphosphines.2 Such C P connections can be made by the
Received 19 December 2007; accepted 1 February 2008.
Dedicated to Professor Marian Mikołajczyk, CBMiM PAN in Ło´dz´, Poland, on the
occasion of his 70th birthday.
This work has been performed within the “PUNCHOrga” interregional network. We
gratefully acknowledge financial support from the “Ministe`re de la Recherche et des Nou-
velles Technologies,” CNRS (Centre National de la Recherche Scientifique), the “Re´gion
Basse-Normandie,” and the European Union (FEDER funding). The authors thank Yann
Munerel, preparing a DUT degree at the Universite´ de Rouen, for some experimental
work.
Address correspondence to Dr. Annie-Claude Gaumont, Laboratoire de Chimie
Mole´culaire et Thioorganique, UMR CNRS 6507, INC3M, FR 3038, ENSICAEN & Uni-
versite´ de Caen, 14050 Caen, France. E-mail: annie-claude.gaumont@ensicaen.fr
846

C
P Cross-Coupling Reaction
847
reaction between halophosphines and vinylic organometallic species.
However, this method shows a lack of tolerance toward various
functional groups. Alternative approaches are hydrophosphination of
alkynes (addition of a P H bond to a C C triple bond) and catalytic
carbon–phosphorus cross-coupling reaction. Hydrophosphination is
the most attractive methodology from both the economic and ecological
points of view and also for its tolerance toward functional groups.1a,3
However, this method cannot lead to the formation of vinylphosphine
containing cycles due to the lack of five- or six-membered ring alkynes.
Moreover, hydrophosphination is sensitive, like various addition
reactions, to steric factors. As our research program aims at developing
uncatalyzed4 or transition metal catalyzed5 transformations for the
construction of C P bonds, a part of our work deals with the synthesis of
various vinylphosphines by hydrophosphination using the convenient
phosphine-borane derivatives.6 However, we also experienced difficulty
in synthesizing bulky derivatives starting from hindered alkynes. In
order to overcome this problem and to provide a general and efficient
access to vinylphosphine derivatives, we turned our attention to the
C P cross-coupling reaction of vinylic derivatives. Different vinylic cou-
pling partners may be used as the electrophilic source: vinylic halides7
and vinylic derivatives derived from the widely available ketones, i.e.,
vinyl triflates8 or tosylates. Vinyl iodides are not widely available, and
chloride and bromide derivatives show a low reactivity in the first step,
i.e., the oxidative addition. We recently showed that acyclic and cyclic
vinyl triflates could be efficiently coupled under mild conditions with
phosphine-boranes having various electronic and steric properties.5a
Indeed, using this methodology, we were able to synthesize various hin-
dered vinylphosphines. The reaction was extended to the synthesis of
enantiopure derivatives starting from ketones derived from the chiral
pool.
We sought to extend this methodology to other enol sulfonates,
readily available from the corresponding ketones: vinyl tosylates.
Although vinyl tosylates are less reactive electrophiles than the
corresponding vinyl triflates, they offer two important advantages.
First, they are generally less expensive than the corresponding
vinyl triflates. Second, vinyl tosylates are stable crystalline solids,
which do not hydrolyze in the presence of residual water as ob-
served with triflates. Furthermore, they are, unlike triflates, eas-
ily purified by silica gel chromatography. To the best of our knowl-
edge, no such example involving the C P cross-coupling reaction
between vinyl tosylates and phosphine derivatives has ever been
reported.

848
D. Julienne et al.
RESULTS AND DISCUSSION
We report here the preliminary results of our investigation on the
palladium-catalyzed C P cross-coupling of vinyl tosylates with phos-
phine derivatives. Knowing that vinyl tosylates are less reactive than
the corresponding vinyl triflates, the reactions were performed with
diphenylphosphine-borane 1, which is a well-known reactive phosphine
derivative.9 Indeed, both phenyl and borane groups are able to activate
the P H bond of the phosphine.
In a preliminary test, we selected the activated vinyl tosylate 2
featuring an electron-withdrawing group in the β-position of the enol
tosylate in order to offset the lack of reactivity of these substrates. 2-
(Ethoxycarbonyl)cyclohex-1-en-1-yl-p-toluenesulfonate 2 was prepared
using the method of Klapars et al.10 Conditions for the coupling are in-
spired by our work on the C P cross-coupling of vinyl triflates.5a Thus,
we selected dpppPdCl2 as the source of palladium, K2CO3 as base, and
DMSO as solvent. The reactions were carried out with a stoichiometric
amount of phosphine 1 and tosylate, unlike with triflate, where a slight
excess of triflate was used to circumvent its partial hydrolysis.5a,11
After 3 h at 60◦C, the crude mixture was analyzed by 31P NMR spec-
troscopy (Table I, entry 1). Although an almost complete conversion
(89%) was observed, only a moderate amount of the expected coupling
product 3 (52%) was obtained together with various unindentified side
products. This result is not so surprising, since we have already ob-
served in a previous work5a that when the coupling conditions are
not optimized, an oxidation–degradation of phosphine-borane 1 takes
place, leading to the formation of side products. To improve the conver-
sion, a higher temperature (80◦C) was tested. Under these conditions,
the reaction was completed in only 3 h affording 3 in 83% (percent-
ages given always correspond, unless otherwise noted, to 31P NMR
proportion) (Table I, entry 2). The same reaction was also carried out
without any catalyst. After 3 h, the expected product 3 was obtained
in significantly lower amount (33%) together with various unindenti-
fied side products (Table I, entry 3). Using palladium acetate in the
absence of a bidentate phosphine ligand also afforded a low amount
of the expected phosphine 3 (61%) together with various unidentified
derivatives (Table I, entry 4). These experiments demonstrate that the
use of a palladium catalyst bearing a bidentate phosphine is required
to promote a clean coupling reaction and thus avoid side reactions.
In order to improve the amount of the expected product 3, reaction
time was decreased to 2 h, then to 1 h, and to 0.5 h (Table I, entries
5–7). In the first two cases (2 h and 1 h), both good conversion (95%)
and amount of the coupling product (83%–85%) were obtained (Table I,

C
P Cross-Coupling Reaction
849
TABLE I C P Cross-Coupling Reaction of Activated Vinyltosylate 2
Coupling product
Entry
T (◦C)
t
Conversiona (%)
3a (%)
1
2
3
4
5
6
7
8
9
60
80
3 h
3 h
3 h
3 h
2 h
89
100
72
99
95
95
71
28
29
66
58
52
83
33b
61
85
83
47
7
80
80c
80
80
80
1 h
0.5 h
5 min
15 min
15 min
1 h
80d
80d
90d
80e
18
21
41
10
11
aConversion and proportion were determined by 31P NMR spectroscopy, breaction
without catalyst, creaction without ligand using Pd(OAc)2as catalyst, dunder microwave
irradiation, ereaction with Ph2PH instead of borane derivative.
entries 4 and 5), while after only half an hour of reaction, incomplete
conversion was observed (Table I, entry 6).
These preliminary results show that the coupling between
diphenylphosphine-borane 1 and tosylate 2 can be performed under
reasonably mild conditions (1 h at 80◦C). In order to lower the con-
sumed energy, we envisioned performing the cross-coupling reaction
under microwave irradiation (Table I, entries 8–10). Our previous work
on the C P cross-coupling reaction has shown that the microwave ac-
tivation was efficient with triflates, phosphine-boranes, and palladium
catalyst allowing a decrease of the reaction time.
However, after both 5 min and 15 min of irradiation at 80◦C, only
a low conversion of 30% was obtained (Table I, entries 8 and 9). Tem-
perature was then increased to 90◦C (Table I, entry 10). After 15 min
of irradiation, a higher conversion of 66% was measured, but a lot of
side products were observed. As no improvement was observed in these
preliminary tests, the microwave activation was abandoned.
It is worth noting that in each previous experiment, the coupling
product was always recovered as the free phosphine, indicating that
deboronation has occurred during the reaction. In order to check if the

850
D. Julienne et al.
borane activation was required for this coupling, diphenylphosphine-
borane 1 was replaced by diphenylphosphine in the coupling reaction
using the optimized conditions (dpppPdCl2, K2CO3, DMSO, 80◦C, 1
h). As anticipated, a lower conversion (58%) was observed compared
to the one obtained with phosphine-borane (95%) (Table I, entry 11
vs. entry 6). Hence, the cross-coupling reaction of vinyl tosylate must
be performed with phosphine-borane complexes to avoid long reaction
time and to limit decomposition.
Finally, the cross-coupling reaction of vinyltosylate
2 with
diphenylphosphine-borane 1 was repeated using the best defined con-
ditions (Scheme 1). After boration, an easy purification by silica gel
flash chromatography in air afforded coupling product 4 in 56% yield.
SCHEME 1
We then turned our attention to the cross-coupling of unactivated
and consequently less reactive vinyl tosylates. We first used 1,1-
diphenylprop-1-en-2-yl-p-toluenesulfonate 5, which is easily prepared
using the method of Klapars et al.10 This tosylate was coupled with
phosphine-borane 1 using the conditions previously defined for cross-
coupling of tosylate 2: dpppPdCl2 as catalyst, K2CO3 as base, and
DMSO as solvent. As anticipated, due to the poor reactivity of 5, only
16% of coupling product 6 was observed after 3 h of reaction at 80◦C
together with a high proportion of side products (Table II, entry 1). Var-
ious conditions were then tested by modifying the reaction parameters
such as the temperature, the reaction time, the catalytic system, the
solvent, and by adding salts. First, the reaction was carried out under
the conditions described above, and potassium iodide (3 equiv.) was
added to the mixture (Table II, entry 2). Previous work in our labora-
tory on the C P cross-coupling reaction of triflates had shown that the
addition of iodide salt facilitated sluggish reactions.5a However with
tosylates, no benefit in the conversion was observed.
Reaction temperature was then increased to 90◦C, 110◦C, and
120◦C keeping the other parameters as previously defined: dpppPdCl2,
K2CO3, DMSO, 3 h (Table II, entries 3–5). At 90◦C, a high conver-
sion (95%) was observed, but with a low coupling product propor-
tion, showing a degradation of the starting material. At increased

C
P Cross-Coupling Reaction
851
TABLE II C P Cross-Coupling Reaction of Vinyltosylate 5
Coupling
Product
6a (%)
Conversiona
Entry
T (◦C)
t
Catalyst
(%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
80
80
90
3 h
3 h
3 h
3 h
3 h
2 h
1 h
2 h
2 h
2 h
2 h
2 h
2 h
2 h
2 h
2 h
2 h
dpppPdCl2
88
61
95
95
96
100
74
100
71
100
97
65
100
100
95
100
94
16
9
dpppPdClb2
dpppPdCl2
dpppPdCl2
dpppPdCl2
dpppPdCl2
dpppPdCl2
dppfPdCl2
Pd(OAc)2/(t-Bu)3P
Pd(OAc)2/Biph(t-Bu)2P
Pd(OAc)2/Biph(Cy)2P
Pd(OAc)2/Biph(t-Bu)2P
dpppPdCl2
dpppPdCl2
dpppPdCl2
Pd(OAc)2/Biph(t-Bu)2P
dpppPdCl2
21
76
54
77
54
27
26
63
37
11
61
55
27
—
59
110
120
110
110
110
110
110
110
90
110d
110e
90e
110e
110f
aConversion and proportion were determined by 31P NMR spectroscopy, badditive
added: KI (3 equiv.), cadditive added: KI (1 equiv.), dadditive added: n-Bu4NI (1 equiv.),
eusing DMF as solvent.
temperatures (110–120◦C), an almost total conversion was obtained,
with a higher proportion of 6 at 110◦C rather than at 120◦C, indicat-
ing a probable decomposition of 6 at high temperature. Consequently,
temperature of 110◦C was kept, and reaction time was decreased to 2
h and 1 h. After 2 h, a complete conversion and a good coupling prod-
uct proportion (77%) were obtained (Table II, entry 6), while after 1 h,
conversion was incomplete (Table II, entry 7).
At the sight of these first results, best conditions are a temperature
of 110◦C for a reaction time of 2 h using conventional oil bath acti-
vation (Table II, entry 6). In order to improve this catalytic system,
various metal/phosphine ligand couples were examined. Electron-poor
ligands such as dppf (dppfPdCl2 complex) provided a lower amount of
the expected coupling product presumably because electron-poor lig-
ands do not favor the oxidative addition step (Table II, entry 8).12
Hence, electron-rich phosphine ligands were tested (Table II, entries
9–12). Unfortunately, a lower proportion of coupling product 6 was

852
D. Julienne et al.
also measured. The best result in this C P coupling reaction is conse-
quently obtained with the simple and inexpensive diphosphine ligand
dppp (Table II, entry 6).
Screening of additives was then conducted. Salts such as KI and n-
Bu4NI were added in the mixture, but whatever the conditions used,
no improvement in the formation of 6 was observed (Table II, entries
13–16). These results confirm that the addition of iodide salts had no
benefit for the cross-coupling reaction of vinyl tosylates.
The influence of the nature of the solvent was then examined. By
analogy with vinyl triflates, the oxidative addition of vinyl tosylates
should lead to cationic palladium species. Our previous work on C P
cross-coupling of vinyl triflates had shown that use of a polar sol-
vent was necessary to ensure fast oxidative addition of vinyl triflate
to Pd(0).5a,13 Consequently, using the previously defined conditions
(dpppPdCl2, K2CO3, 110◦C, 2 h), DMSO was replaced by DMF (Table
II, entry 17). No improvement was noted.
Finally, cross-coupling reaction between vinyl tosylate 5 and
diphenylphosphine-borane 1 was repeated under optimized conditions
(Scheme 2). After boration and purification, coupling product 7 was
isolated in 62% yield.
SCHEME 2
The coupling reaction was extended to the unactivated cyclohex-1-
en-1-yl-p-toluenesulfonate 8. Reaction was carried out using optimized
conditions developed for the cross-coupling of vinyl tosylate 5. After
boration and purification, coupling product 9 was isolated in 74% yield
(Scheme 3).
SCHEME 3

C
P Cross-Coupling Reaction
853
CONCLUSION
To conclude, we have shown that vinyl tosylate can be efficiently cou-
pled with diphenylphosphine-borane using a simple and inexpensive
catalytic system such as dpppPdCl2. The best-defined conditions in-
volved a weak base, K2CO3, a polar solvent (DMSO), and a temper-
ature between 80◦C and 110◦C. Vinyl tosylate bearing an electron-
withdrawing group can be coupled under conditions quite similar to
vinyl triflates. Less reactive vinyl tosylates were also successfully cou-
pled, although a higher temperature was required (110◦C). It is worth
noting that this methodology allows us, for the first time, to generate
vinylphosphine derivatives from easily accessible enol tosylates, which
are known to be rather poor electrophiles.
EXPERIMENTAL
All reactions were carried out under nitrogen atmosphere, and all
glassware was flame dried before use. Vinyl tosylates10 2 and 5 and
phosphine-borane 1[14] precursors were prepared according to litera-
ture procedures. Dimethylsulfoxide was distilled from calcium hydride
and degassed before use.
The microwave oven used was a CEM Discover with a power up to
300 W. The software used was ChemDriver. Reactions were carried out
by setting temperature and a power threshold of 30 W.
Column chromatography was performed on Merck silica gel Si 60
(40–63 µm). Solvents were used as purchased. Thin layer chromatog-
raphy (TLC) was performed on silica gel 60 F-254 plates (0.1 mm) with
iodine or UV detection.
1H and 13C NMR chemical shifts are reported relative to Me4Si as an
internal standard. 31P and 11B NMR chemical shifts are reported rela-
tive to H3PO4 (85%) and BF3.Et2O as external references, respectively.
Coupling constants are reported in Hertz (Hz). Abbreviations are used
as follows: s = singlet, d = doublet, t = triplet, q = quartet, sept =
septet, oct = octet, and m = multiplet.
Melting points were measured with an Electrotherma IA 9200 ap-
paratus and are given without correction.
Mass spectroscopy was performed with a Waters QTOF APCI
instrument.
Cyclohex-1-en-1-yl-p-toluenesulfonate 815
In a two-necked round-bottomed flask equipped with a thermometer
and a nitrogen inlet, HMDS (2.25 mL, 10.6 mmol, 1.1 equiv.) is dissolved

854
D. Julienne et al.
in anhydrous THF (15 mL). The solution is cooled to –50◦C, and n-BuLi
(4.24 mL, 2.5 M in hexane, 10.6 mmol, 1.1 equiv.) is slowly added. After
15 min, a solution of cyclohexanone (1 mL, 9.6 mmol) in anhydrous
THF (15 mL) is added, and the mixture is stirred at –50◦C for 2 h. A
solution of p-tolylsulfonic anhydride (3.46 g, 10.6 mmol, 1.1 equiv.) in
anhydrous THF (15 mL) is added. The mixture is stirred for 15 min
at –50◦C and for 2 h at 0◦C. The mixture is then concentrated under
reduced pressure, and MTBE (50 mL) is added. The organic layer is
washed with aqueous 2M NaHCO3 (50 mL) and water (3 × 50 mL),
dried over MgSO4, filtered, and concentrated under reduced pressure.
The crude product is purified by silica-gel column chromatography with
pentane:AcOEt (95:5, Rf = 0.24) as eluent giving a white solid (1.6 g,
1
3
65 %), mp = 24◦C. H NMR (250.1 MHz, CDCl3): δ = 7.73 (d, JHH
=
3
8.3 Hz, 2H), 7.26 (d, JHH = 8.3 Hz, 2H), 5.31–5.24 (m, 1H), 2.38 (s,
3H), 2.05–1.88 (m, 4H), 1.61–1.49 (m, 2H), 1.48–1.36 (m, 2H). 13C NMR
(62.9 MHz, CDCl3): δ = 148.2, 144.8, 133.7, 129.6, 128.2, 117.2, 27.6,
23.8, 22.7, 21.7, 21.3. HRMS Calcd. for C13H16O3S [M+H]+: 253.0898.
Found: 253.0901.
(2-(Ethoxycarbonyl)cyclohex-1-en-1-yl)diphenylphosphine-
borane 4
In
a Schlenk tube, flushed under nitrogen, dpppPdCl2 (16.5
mg, 0.03 mmol, 5.6 mol %) is dissolved in DMSO (1 mL). 2-
(Ethoxycarbonyl)cyclohex-1-en-1-yl-p-toluenesulfonate 2 (162 mg, 0.50
mmol), K2CO3 (83 mg, 0.60 mmol, 1.2 equiv.), and phosphine-borane 1
(100 mg, 0.50 mmol) are introduced. The mixture is heated to 80◦C for 3
h. After cooling to room temperature, BH3·SMe2 is added up to complete
boration of the product if a partial decomplexation has occurred during
the reaction. The mixture is stirred for 30 min and hydrolyzed with
1 mL of degassed water. The aqueous layer is extracted with diethyl
ether (3 × 2 mL). The combined organic layers are dried over MgSO4
and concentrated under reduced pressure. The crude product is then
purified by silica-gel column chromatography with toluene (Rf = 0.27)
as eluent giving a red viscous oil (99 mg, 56%). 31P NMR (161.9 MHz,
CDCl3): δ = 24.1–21.3 (m). 1H NMR (400.1 MHz, CDCl3): δ = 7.65–7.58
3
(m, 4H), 7.43–7.32 (m, 6H), 3.33 (q, JHH = 7.2 Hz, 2H), 2.45–2.37 (m,
2H), 2.09–2.00 (m, 2H), 1.77–0.51 (m, 3H), 1.68–1.60 (m, 2H), 1.60–1.51
(m, 2H), 0.89 (t, 3JHH = 7.2 Hz, 3H). 13C NMR (100.6 MHz, CDCl3): δ =
3
2
2
168.2 (d, JPC = 6.9 Hz), 144.2 (d, JPC = 1.9 Hz), 133.2 (d, JPC = 9.6
Hz), 131.0 (d, 4JPC = 2.4 Hz), 129.3 (d, 1JPC = 46.2 Hz), 128.5 (d, 1JPC
=
3
3
57.5 Hz), 128.4 (d, JPC = 10.2 Hz), 60.9, 29.7 (d, JPC = 8.2 Hz), 29.1

C
P Cross-Coupling Reaction
855
(d, 2JPC = 10.7 Hz), 22.2 (d, 3JPC = 7.4 Hz), 21.1, 13.4. 11B NMR (128.4
MHz, CDCl3): δ = –31.6 to –36.2 (m). HRMS Calcd. for C21H25O2BP
[M-H]+: 351.1685. Found: 351.1670.
Preparation of Vinylphosphine-Boranes from Unactivated
Vinyl Tosylates: General Procedure
In a Schlenk tube, flushed under N2, dpppPdCl2 (5.6 mol %) is dissolved
in DMSO. Vinyl tosylate (1 equiv.), K2CO3 (1.2 equiv.) and phosphine-
borane 1 (1 equiv.) are introduced. The mixture is heated to 110◦C for
2 h. After cooling to room temperature, BH3·SMe2 is added up to com-
plete boration of the product if a partial decomplexation has occurred
during the reaction. The mixture is stirred for 30 min and hydrolyzed
with degassed water. The aqueous layer is extracted with diethyl ether.
The combined organic layers are dried over MgSO4 and concentrated
under reduced pressure. The crude product is then purified by silica-gel
column chromatography.
(1,1-Diphenylprop-1-en-2-yl)diphenylphosphine-borane16
dpppPdCl2 (14.9 mg, 0.025 mmol), DMSO (0.9 mL), 1,1-diphenylprop-
1-en-2-yl-p-toluenesulfonate 5 (164.2 mg, 0.45 mmol), K2CO3 (74.7 mg,
0.54 mmol), diphenylphosphine-borane 1 (90 mg, 0.45 mmol), degassed
water (1 mL), diethyl ether (3 × 2 mL). Eluent: toluene:pentane (60:40),
Rf = 0.50, yield: 62% (110 mg), red powder, mp = 130◦C.
(Cyclohex-1-en-1-yl)diphenylphosphine-borane 916
dpppPdCl2 (14.9 mg, 0.025 mmol), DMSO (0.9 mL), cyclohex-1-en-1-
yl-p-toluenesulfonate 8 (113.7 mg, 0.45 mmol), K2CO3 (74.7 mg, 0.54
mmol), diphenylphosphine-borane 1 (90 mg, 0.45 mmol), degassed wa-
ter (1 mL), diethyl ether (3 × 2 mL). Eluent: pentane:AcOEt (80:20),
Rf = 0.80, yield: 74% (93 mg), red powder, mp = 95◦C.
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[16] For full characterization see reference [5a].