The dehydrochlorination of either 1, 2-dichloro-1-methylcyclopropane or 1-bromo-2-chloro-2- methylcyclopropane with potassium t-butoxide yields 2-t-butoxy-1-methylenecyclopropane. These results are interpreted in terms of methylenecyclopropene as a reactive intermediate which is trapped by addition of nucleophile (t-butoxide) to the cyclopropenyl double bond. The introduction of methanethiol to the reaction medium yields 2-thiomethyl-1- ...