B(C6F5)3-Catalyzed Reduction of Ketones and Imines
ployed; cyclohexane/tert-butyl methyl ether (TBME) or cyclohex-
ane/ethyl acetate solvent mixtures were used as eluents. 1H, 13C and
29Si NMR spectra were recorded in CDCl3 or C6D6 on Bruker AV
300, Bruker AV 400, Varian INOVA 500 and Varian Unity plus
600 spectrometers. GLC analyses were performed using a Shim-
adzu GC-17A equipped with a SE-54 capillary column (30 m
ϫ0.32 mm, 0.25 µm, N2 carrier gas, 250 °C injection temperature,
detector temperature 300 °C; temperature program: start tempera-
ture 40 °C for 1 min, heat rate 10 °C min–1, 280 °C end temperature
for 10 min). HPLC analysis was performed with an Agilent 1200
instrument on a chiral stationary phase using a Daicel Chiralcel
OD-H column (n-heptane/iPrOH as a solvent). Mass spectra were
recorded with Waters Micromass Quattromicro (GC-MS/EI) or
Bruker Daltronics Micro-TOF (ESI-MS). IR spectra were recorded
on a Varian 3100 FT-IR instrument equipped with an ATR unit.
Elemental analyses were conducted on a Vario EL III instrument
from Elementaranalysensysteme GmbH (Hanau, Germany). Ana-
lytical data for (SiR*,R*)-10 was included in a preliminary re-
port.[13]
(
SiR*,R*)-1-Isopropyl-1-(1-naphth-1-ylethoxy)-1-silatetraline
[(SiR*,R*)-18]: See Table 1, entry 3. According to GP 1, starting
from 13 (68.7 mg, 0.404 mmol), rac-8 (66.5 mg, 0.350 mmol), and
B(C6F5)3 (1) (10.4 mg, 0.0203 mmol) compound (SiR*,R*)-18
1
(79 mg, 63%, dr = 77:23 by H NMR spectroscopy) was obtained
as a colorless, highly viscous oil. Rf = 0.60 (cyclohexane/tert-butyl
methyl ether = 24:1). GLC (SE-54): tR = 24.0 (minor diastereomer),
24.1 min (major diastereomer); NMR spectroscopic data for major
diastereomer: 1H NMR (400 MHz, CDCl3): δ = 0.59 (ddd, J =
15.1, J = 7.9, J = 4.2 Hz, 1 H), 0.74 (ddd, J = 15.1, J = 10.4, J =
4.7 Hz, 1 H), 1.00 (d, J = 7.0 Hz, 3 H), 1.14 (d, J = 6.8 Hz, 3 H),
1.15–1.25 (m, 1 H), 1.53 (d, J = 6.4 Hz, 3 H), 1.59–1.68 (m, 1 H),
1.75–1.86 (m, 1 H), 2.58 (ddd, J = 15.9, J = 9.5, J = 3.1 Hz, 1 H),
2.68 (ddd, J = 15.9, J = 7.5, J = 3.0 Hz, 1 H), 5.48 (q, J = 6.2 Hz,
1 H), 7.15 (d, J = 7.5 Hz, 1 H), 7.28 (dd, J = J = 7.2 Hz, 1 H) 7.35
(ddd, J = J = 7.4, J = 1.6 Hz, 1 H), 7.40–7.51 (m, 3 H), 7.76–7.81
(m, 3 H), 7.79–7.84 (m, 1 H), 8.00 (dd, J = 6.8, J = 2.6 Hz, 1 H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 9.6, 14.2, 17.1, 17.2, 23.2,
26.6, 35.5, 68.9, 122.9, 123.6, 125.3, 125.4, 125.7 (2ϫ), 127.3, 128.6,
128.9, 129.7, 130.0, 132.1, 133.9, 134.7, 142.5, 150.5 ppm. NMR
spectroscopic data for minor diastereomer: 1H NMR (400 MHz,
CDCl3): δ = 0.86–1.11 (m, 8 H), 1.15–1.25 (m, 1 H), 1.57 (d, J =
6.4 Hz, 3 H), 1.86–1.96 (m, 1 H), 1.96–2.08 (m, 1 H), 2.63–2.73 (m,
1 H), 2.80 (ddd, J = 16.1, J = 7.2, J = 2.9 Hz, 1 H), 5.58 (q, J =
6.4 Hz, 1 H), 7.00 (dd, J = 7.4 Hz, 1 H), 7.11 (d, J = 7.5 Hz, 1 H),
7.23 (ddd, J = J = 7.5, J = 1.4 Hz, 1 H), 7.40–7.51 (m, 3 H), 7.76–
7.81 (m, 3 H), 7.79–7.84 (m, 1 H), 7.97 (m, 1 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 10.5, 14.1, 17.1, 17.3, 23.1, 26.6, 35.6, 69.0,
122.9, 123.6, 125.2 (2ϫ), 125.6, 125.7, 127.4, 128.6, 128.9, 129.5,
General Procedure for the Hydrosilylation of Ketones (GP 1): A
Schlenk tube is charged with B(C6F5)3 (1) (0.04–0.10 equiv.) in a
glovebox. After connection to an argon/vacuum manifold, the solid
is dissolved in anhydrous degassed toluene forming a colorless solu-
tion. Subsequently, solutions of the ketone (1.05 equiv.) and the
silane (1.00 equiv.) in toluene are added dropwise via syringe. The
resulting solution (0.1 in silane) is maintained at ambient tem-
perature until complete consumption of the reactants (1.00 to 18.5
h) as monitored by GLC. After addition of cyclohexane (10 mL)
and a small portion of silica gel the solvents are evaporated. Purifi-
cation by flash column chromatography on silica gel (mixtures of
cyclohexane/tert-butyl methyl ether) affords the analytically pure
products as colorless, highly viscous oils or solids.
130.0, 131.5, 133.9, 134.8, 142.3, 150.0 ppm. IR (ATR): ν = 3052
˜
(w), 2923 (m), 2863 (m), 1590 (w), 1092 (s) cm–1. HRMS (ESI):
calcd. for C24H28OSiNa [[M + Na]+]: 383.1802; found 383.1813.
C24H28OSi (360.56): calcd. C 79.95, H 7.83; found C 80.01, H 7.82.
(
SiR*,R*)-1-Isopropyl-1-(1-naphth-2-ylethoxy)-1-silatetraline
[(SiR*,R*)-17]: See Table 1, entry 2. According to GP 1, starting
from 12 (71.5 mg, 0.420 mmol), rac-8 (74.5 mg, 0.400 mmol), and
B(C6F5)3 (1) (11.1 mg, 0.0217 mmol) compound (SiR*,R*)-17
(78 mg, 54%, dr = 73:27 by GLC) was obtained as a colorless,
highly viscous oil. Rf = 0.57 (cyclohexane/tert-butyl methyl ether =
24:1). GLC (SE-54): tR = 24.5 (minor diastereomer), 24.7 min
(SiR*,R*)-1-Isopropyl-1-(1-mesitylethoxy)-1-silatetraline [(SiR*,R*)-
19]: See Table 1, entry 4. According to GP 1, starting from 14
(71.1 mg, 0.438 mmol), rac-8 (74.4 mg, 0.400 mmol), and B(C6F5)3
(1) (10.4 mg, 0.0203 mmol) compound (SiR*,R*)-19 (123 mg, 87%,
1
dr = 80:20 by H NMR spectroscopy) was obtained as a colorless,
(major diastereomer). NMR spectroscopic data for major dia-
stereomer: H NMR (400 MHz, CDCl3): δ = 0.65 (ddd, J = 15.0, = 98:2). GLC (SE-54): tR = 21.8 min (both diastereomers). NMR
J = 7.9, J = 4.3 Hz, 1 H), 0.75 (ddd, J = 15.0, J = 10.4, J = 4.7 Hz,
highly viscous oil. Rf = 0.16 (cyclohexane/tert-butyl methyl ether
1
spectroscopic data for major diastereomer: 1H NMR (500 MHz,
1 H), 0.86–1.23 (m, 7 H), 1.42 (d, J = 6.6 Hz, 3 H), 1.58–1.72 (m, CDCl3): δ = 0.52 (dddd, J = 15.0, J = 8.2, J = 4.2, J = 0.9 Hz, 1
1 H), 1.76–1.93 (m, 1 H), 2.57 (ddd, J = 16.0, J = 9.6, J = 2.9 Hz, H), 0.74 (ddd, J = 15.0, J = 10.4, J = 4.6 Hz, 1 H), 0.95–1.14 (m,
1 H), 2.62–2.72 (m, 1 H), 4.92 (q, J = 6.4 Hz, 1 H), 7.13 (d, J = 7 H), 1.41 (d, J = 6.8 Hz, 3 H), 1.47–1.56 (m, 1 H), 1.75–1.83 (m,
7.2 Hz, 1 H), 7.25 (dd, J = J = 7.2 Hz, 1 H), 7.32 (ddd, J = J =
7.5, J = 1.6 Hz, 1 H), 7.40–7.49 (m, 3 H), 7.64–7.84 (m, 5 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 9.8, 14.2, 17.1, 17.2, 23.1, 27.1,
35.5, 71.2, 123.7, 124.2, 125.4, 125.6, 126.0, 127.8, 128.0, 128.1,
128.5, 129.7, 132.1, 132.8, 133.4, 134.7, 144.2, 150.1 ppm. NMR
spectroscopic data for minor diastereomer: 1H NMR (400 MHz,
CDCl3): δ = 0.86–1.23 (m, 9 H), 1.47 (d, J = 6.6 Hz, 3 H), 1.76–
1.93 (m, 1 H), 1.94–2.01 (m, 1 H), 2.62–2.72 (m, 1 H), 2.79 (ddd,
J = 15.9, J = 7.3, J = 2.9 Hz, 1 H), 4.99 (q, J = 6.8 Hz, 1 H), 7.03
1 H), 1.95–2.50 (br. s, 9 H), 2.59 (ddd, J = 16.0, J = 9.2, J = 3.2 Hz,
1 H), 2.61 (ddd, J = 16.0, J = 7.6, J = 3.3 Hz, 1 H), 5.12 (q, J =
6.8 Hz, 1 H), 6.76 (br. s, 2 H), 7.13 (d, J = 7.5 Hz, 1 H), 7.25 (dd,
J = J = 7.2 Hz, 1 H), 7.32 (ddd, J = J = 7.5, J = 1.6 Hz, 1 H), 7.64
(dd, J = 7.2, J = 1.6 Hz, 1 H) ppm. 13C NMR (125 MHz, CDCl3):
δ = 10.0, 14.3, 17.1, 17.2, 20.4, 20.9, 23.1 (2ϫ), 35.6, 68.2, 125.4,
128.7, 129.6, 129.9, 132.0, 134.6, 135.5, 136.0, 138.3, 150.1 ppm.
NMR spectroscopic data for minor diastereomer: 1H NMR
(500 MHz, CDCl3): δ = 0.83–0.92 (m, 1 H), 0.95–1.14 (m, 8 H),
(dd, J = J = 7.3 Hz, 1 H), 7.11 (d, J = 7.5 Hz, 1 H), 7.20–7.28 (m, 1.45 (d, J = 6.8 Hz, 3 H), 1.85–1.95 (m, 1 H), 1.95–2.50 (br. s, 10
1 H), 7.36 (dd, J = 7.3, J = 1.3 Hz, 1 H), 7.40–7.49 (m, 3 H), 7.64– H), 2.68 (ddd, J = 15.9, J = 9.8, J = 2.9 Hz, 1 H), 2.82 (ddd, J =
7.84 (m, 4 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 10.5, 14.1, 16.0, J = 7.4, J = 2.8 Hz, 1 H), 5.15 (q, J = 6.8 Hz, 1 H), 6.73 (br.
17.1, 17.3, 23.1, 27.0, 35.6, 71.3, 123.8, 124.2, 125.2, 125.5, 126.0,
127.7, 127.9, 128.1, 128.6, 129.5, 131.5, 132.8, 133.4, 134.8, 144.0,
s, 2 H), 6.98 (dd, J = J = 7.5 Hz, 1 H), 7.11 (d, J = 7.5 Hz, 1 H),
7.17 (dd, J = 7.5, J = 1.6 Hz, 1 H), 7.24 (ddd, J = J = 7.5, J =
1.6 Hz, 1 H) ppm. 13C NMR (125 MHz, CDCl3): δ = 10.7, 14.0,
17.1, 17.2, 20.4, 20.9, 23.2, 23.3, 35.7, 68.3, 125.2, 128.3, 129.6,
150.1 ppm. IR (ATR): ν = 3055 (m), 2923 (m), 2862 (m), 1602 (w),
˜
1086 (s) cm–1. HRMS (ESI): calcd. for C24H28OSiNa [[M + Na]+]:
383.1802; found 383.1801. C24H28OSi (360.56): calcd. C 79.95, H
7.83; found C 80.04, H 7.95.
129.9, 131.6, 134.8, 135.5, 135.7, 138.3, 150.3 ppm. IR (ATR): ν =
˜
2923 (s), 2863 (m), 1612 (w), 1085 (s) cm–1. HRMS (ESI): calcd. for
Eur. J. Org. Chem. 2009, 5047–5056
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5053