Alkyl/halogen substitution in carbenes (carbenoids): a route to new cyclopropane derivatives

7-Halo-7-methylnorcaranes (I) and 7,7-dimethylnorcarane (II) are formed via replacement of halogen by Me during the reaction of cyclohexene (III) with carbenes (carbenoids) and MeLi. Thus, III is treated with CHClF2 or CCl2F2 and MeLi to give a mixt. of 7-chloro-7-fluoronorcarane (IV), I, and II. 1,1-Difluoro-2,2-dimethylcyclopropanes (V) are obtained from Me2C:CHMe and Me2C:CH(CH2)2CH(OEt)2. [on SciFinder (R)]