My PhD dissertation - Institut Fresnel

107
(+)-(M)-Dimethyl-6,6’-dibromobiphenyl-2,2’-dicarboxylate (M-38): Prepared following
the same protocol, starting from (+)-(M)-6,6’-dibromobiphenyl-2,2’-dicarboxylic acid (37);
20
D
m.p. 103 - 105 °C; [ α ] = +5.8 (c = 0.51, acetone).
C16H12Br2O4 (428.07) calcd. C 44.89% H 2.83%
found C 44.65% H 2.67%.
(±)-(PM)-(6,6’-Dibromobiphenyl-2,2’-diyl)dimethanol (39): Prepared following the
procedure described by R. Schmid et al. [15] , starting from (±)-(PM)-dimethyl-6,6’-
dibromobiphenyl-2,2’-dicarboxylate (38; 3.0 g, 7.0 mmol); colorless prisms; m.p. 130 -
132 °C (ref. [15] m.p. 134 - 136 °C); yield: 2.19 g (84%).
(-)-(P)-(6,6’-Dibromobiphenyl-2,2’-diyl)dimethanol (P-39): Prepared following the same
protocol, starting from (-)-(P)-dimethyl-6,6’-dibromobiphenyl-2,2’-dicarboxylate (38); m.p.
[ ] 20
19
107 - 108 °C; α = -43.2 (c = 0.5, ethanol); ee > 99% (determined by F NMR analysis of
D
the enantiomerically pure Mosher ester derivative, in comparison with a racemic mixture of
the ester).
(+)-(6,6’-Dibromobiphenyl-2,2’-diyl)dimethanol (M-39): Prepared following the same
protocol, starting from (+)-(M)-dimethyl-6,6’-dibromobiphenyl-2,2’-dicarboxylate (38); m.p.
[ ] 20
19
105 - 107 °C; α = +41.9 (c = 0.51, ethanol). ee ≥ 98% (determined by F NMR analysis
D
of the enantiomerically pure Mosher ester derivative, in comparison with a racemic mixture of
the ester).
Preparation of Mosher ester derivative of (-)-(P)-(39) and (+)-(M)-(39): Under inert
atmosphere, the diol (39, 0.17 g, 0.45 mmol) was dissolved in a mixture of carbon
tetrachloride (2.0 mL) and pyridine (2.0 mL) at 25 °C and (R)-(-)-α-methoxy-α-
(trifluoromethyl)-phenylacetyl chloride (0.25 mL, 0.34 g, 1.35 mmol) was added. The
mixture was stirred for 20 h and the completion of the reaction was monitored by TLC.
N,N-dimethylethanolamine (0.1 mL, 9.0 mg, 1.0 mmol) and the mixture was stirred for a
further 30 min. Dichloromethane (5.0 mL) and 1.0 M hydrochloric acid (5.0 mL) were
added and phases were decanted. The organic layer was washed with brine, dried with
sodium sulfate and evaporated to dryness to afford a slightly yellow oil; yield: 347 mg
(96%).