FULL PAPER
temperature. The tube was tightly closed, shaken, and then
NMR spectroscopies were recorded. H NMR (600 MHz, d-o-
Acknowledgements
1
Dichlorobenzene) δ 7.66 (d, J=8.4 Hz, 1H), 7.59 (dd, J=6.9,
1.4 Hz, 1H), 7.56 (dd, J=8.1, 1.4 Hz, 1H), 7.49–7.36 (m, 10H),
7.31–7.24 (m, 4H), 7.23 (dd, J=8.1, 6.9 Hz, 1H), 7.18–7.10
(m, 6H), 7.11–7.05 (m, 3H), 7.05–7.00 (m, 6H), 6.93 (d, J=
8.4 Hz, 1H), 5.41 (s, 1H), 2.38 (s, 3H), 1.73–1.66 (m, 2H), 1.02
(d, J=7.5 Hz, 6H), 0.87 (d, J=7.5 Hz, 6H). 13C NMR
(151 MHz, d-o-Dichlorobenzene) δ 158.6, 151.5, 148.7 (d, J=
241.8 Hz), 144.0, 138.5 (d, J=245.6 Hz), 137.0, 136.6 (dm, J=
245.0 Hz), 136.6, 135.8 (d, J=2.9 Hz), 132.7 (d, J=12.1 Hz),
131.3, 129.7 (d, J=13.8 Hz), 129.5, 128.4, 126.4, 126.4, 125.4,
122.6, 122.2, 121.5, 57.2, 24.6, 17.6, 17.4, 14.9. The C-ipso
The Agence Nationale de la recherche (ANR-16-CE07-0018-
01), the University of Bordeaux (UBx), and the CNRS are
gratefully acknowledged for financial support. We are indebted
to the CESAMO for NMR and mass spectroscopy analysis.
References
b) V. S. C. de Andrade, M. C. S. de Mattos, Curr. Org.
Synth. 2015, 12, 309–327; c) B. E. Maryanoff, A. B.
À
atoms of B(C6F5)4 are not observed due to considerable
broadening while coupling with the quadrupolar boron nuclei.
29Si INEPT NMR (60 MHz, d-o-Dichlorobenzene) δ 25.51 (d,
J=19.4 Hz). 15N (1H-15N HMBC) NMR (41 MHz, d-o-Dichlor-
obenzene) δ 304.1. 11B {1H} NMR (96 MHz, d-o-Dichloroben-
zene) δ À 16.2. 19F {1H} NMR (470 MHz, d-o-Dichloroben-
zene) δ À 132.6–À 133.2 (m, 8F), À 163.5 (t, J=20.4 Hz, 4F),
À 167.3 (t, J=19.3 Hz, 8F). 31P NMR (122 MHz, d-o-Dichlor-
obenzene) δ 52.7.
[2] a) P. C. J. Kamer, P. W. N. M. van Leeuwen, Phosphorus
(III) Ligands in Homogeneous Catalysis: Design and
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General procedure for the reduction of phosphine oxides. In
a glovebox under argon atmosphere, a solution of Ph3C+
[B(C6F5)4]À (16.6 mg, 0.018 mmol, 0.05 eq.) in d8-toluene
(0.3 mL), was added to the dry phosphine oxide (0.36 mmol,
1.0 eq.) and then injected into a dry J-Young NMR tube.
Deuterated solvent (0.4 mL) was used to wash the vials and
complete the tube at room temperature. Then PhSiH3 (0.09 mL,
0.72 mmol, 2.0 eq.) (2.0 eq./P=O function in the molecule) was
added into the tube at room temperature. The tube was tightly
°
closed, shaken, and transferred to an oil bath pre-heated at 80 C
and the reaction monitored through 31P NMR analysis. The
reaction was carefully quenched with 1:1 MeOH/Et3N mixture
(1 mL) [Caution: exothermic reaction with gas release]. The
resulting mixture was concentrated under reduced pressure. The
residue was purified by flash chromatography on silica gel with
petroleum ether/ethyl acetate as eluent to give pure phosphine.
In selected cases the purification is performed through recrystal-
lization in hot methanol or by filtration.
General procedure for the formation of phosphine-borane
adducts. For very sensitive phosphines, the above procedure
was followed, until complete conversion monitored by 31P
NMR. The reaction mixture was then put back into the
glovebox and BH3.THF (1 mL) added dropwise. After 12 h at
room temperature, 31P NMR analysis was performed and
showed complete formation of the phosphine-borane adduct.
The reaction mixture was then carefully poured onto silica gel
into an Erlenmeyer inside the glovebox. The flask was washed
with toluene. The reaction mixture was filtered through a
Buchner funnel outside glovebox and then washed with EtOAc
and concentrated under reduced pressure. The residue was
purified by flash chromatography on silica gel with petroleum
ether/ethyl acetate as eluent to give the pure phosphine-borane
adduct.
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[11] H. Fritzsche, U. Hasserodt, F. Korte, G. Friese, K.
Adv. Synth. Catal. 2021, 363, 1–10
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