Resolution of racemic aryl dichloromethyl sulfoxides with (−)-menthone

The addition reaction of the sodium α-sulfinyl carbanion of a racemic aryl dichloromethyl sulfoxide to (−)-menthone in the presence of boron trifluoride diethyl etherate gave an adduct as a mixture of two easily separable diastereomers. After separation of the diastereomers, they were each treated with sodium hydride to afford enantiomerically pure aryl dichloromethyl sulfoxides and (−)-menthone both in high yields. This procedure provides a simple and efficient method for the resolution of racemic aryl dichloromethyl sulfoxides.

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(S)-Dichloromethyl p-tolyl sulfoxideC8H8Cl2OSEe = 99%[α]D28=+172.3 (c 0.36, acetone)Source of chirality: (−)-menthoneAbsolute configuration: (S)

(S)-Dichloromethyl phenyl sulfoxideC7H6Cl2OSEe = 97%[α]D29=+152.3 (c 0.50, acetone)Source of chirality : (−)-menthoneAbsolute configuration: (S)

(S)-Dichloromethyl 2-naphthyl sulfoxideC11H8Cl2OSEe = 99%[α]D29=+182.8 (c 0.30, acetone)Source of chirality: (−)-menthoneAbsolute configuration: (S)

(S)-Dichloromethyl 4-methoxyphenyl sulfoxideC8H8Cl2O2SEe = 98%[α]D29=+152.8 (c 0.30, acetone)Source of chirality: (−)-menthoneAbsolute configuration: (S)

(S)-Dichloromethyl 4-chlorophenyl sulfoxideC7H5Cl3OSEe = 99%[α]D27=+160.6 (c 0.25, acetone)Source of chirality: (−)-menthoneAbsolute configuration: (S)

(S)-Dichloromethyl 4-nitrophenyl sulfoxideC7H5Cl2NO3SEe = 99%[α]D28=+153.6 (c 0.30, acetone)Source of chirality: (−)-menthoneAbsolute configuration: (S)