Carbon tetrachloride–dimethyl sulphone–potassium hydroxide–t-butyl alcohol: a convenient new reagent for gem-dichloromethylenation of alkenes

Abstract

The action of dimethyl sulphone–potassium hydroxide–t-butyl alcohol on carbon tetrachloride readily affords dichlorocarbene. In the presence of alkenes, gem-dichlorocyclopropanes are formed in moderate to high yields. The dichlorocarbene generated by this procedure adds stereospecifically to alkenes with retention of geometric configuration about the carbon–carbon double bond. Relative reactivities of alkenes towards the CCl₄-derived dichlorocarbene parallel the nucleophilicities of the alkenes and indicate that free dichlorocarbene is probably involved.