S. Jones, J. C. C. Atherton / Tetrahedron: Asymmetry 11 (2000) 4543–4548
4547
were recorded on a Bruker AC200 spectrometer using the Bruker Aspect 3000 system. Residual
1
proton signals from chloroform ( H 7.25 ppm) was used as a reference. Coupling constants were
measured in Hz. Specific rotations were determined on a Polaar 2001 automatic polarimeter at
−
1
2
−1
5
89 nm and measured at 20°C unless otherwise stated. [h] values are given in 10 deg cm g .
D
HPLC was carried out using a Beckman System Gold instrument with a Chiralcel OD (4.8×250
3
mm) column and IPA in heptane as the solvent system. The flow rate was 1.00 cm per minute
and the detector was set at 254 nm. Gas chromatography was carried out on a Packard Model
4
27 instrument using a flame ionisation detector. A fused silica capillary column was used with
b-cyclodextrin as the stationary phase. Hydrogen was used as the carrier gas. N-Benzyl and
6,7
N-methyl-(1R)-amino-(2S)-indanol were prepared by literature methods.
4
.1. General procedure for the preparation of the B-methyl catalysts
3
Trimethylboroxine (0.19 cm , 1.34 mmol) was added to a solution of the (1R)-amino-(2S)-
3
indanol (2.01 mmol) in toluene (10 cm ) and stirred at room temperature for 30 minutes.
3
3
Toluene (10 cm ) was added and the resulting solution was concentrated to approximately 2 cm
by distillation. This process was repeated twice after which the toluene was removed under
3
reduced pressure to give the catalyst as a white solid. THF (2 cm ) was added to produce an
approximately 1.0 M solution of catalyst in THF that was used in subsequent reactions. This
solution was found to be stable for a limited period (48 hours) at room temperature when stored
under a nitrogen atmosphere.
4
.2. Optimised procedure for the reduction of aryl ketones
3
BH ·DMS (0.45 cm , 4.71 mmol) was added to a solution of B-methyl-(1R)-amino-(2S)-
3
3
3
indanol (0.42 cm , 0.43 mmol) in THF (4 cm ) and stirred at room temperature under N for 30
minutes. The resulting solution was cooled to 0°C and the ketone (4.29 mmol) in THF (3 cm )
2
3
added via cannula. The reaction mixture was stirred for a further 2 hours at 0°C then quenched
with methanol and allowed to warm to room temperature for 10 minutes. Water was added and
the solvent removed under reduced pressure to leave the product in aqueous phase. The product
3
was extracted into dichloromethane (3×10 cm ), the organic phase washed with 1 M HCl, water
and dried over MgSO . Removal of the solvent produced the product as a slightly cloudy
4
colourless oil in most cases.
4
.2.1. 1-Phenylethanol 1
lH 7.31–7.08 (5H, m, ArH), 4.80 (1H, q, J 6.5, CHOH), 1.97 (1H, br, OH), 1.41 (3H, d, J 6.5,
CH CH); [h] −46.8 (c 1, CHCl ); e.e. 82% (5% IPA in heptane).
3
D
3
4
.2.2. 1-Phenylpropan-1-ol 9
lH 7.31–7.14 (5H, m, ArH), 4.50 (1H, t, J 6.6, CHOH), 1.96 (1H, br, OH), 1.70 (2H, m,
CH CH ), 0.83 (3H, d, J 6.6, CH CH); [h] −36.6 (c 1, CHCl ); e.e. 69% (5% IPA in heptane).
2
3
3
D
3
4
.2.3. 2-Chloro-1-phenylethanol 10
l 7.39–7.25 (5H, m, ArH), 4.88 (1H, dd, J 3.7 and 8.6, CHOH), 3.69 (2H, m, CH Cl), 2.74
H
2
(
1H, br, OH); [h] −53.4 (c 1, CHCl ); e.e. 87% (5% IPA in heptane).
D
3