Unusual behaviour of 2-methyladamantane during bromination

Abstract

As well as 1-bromo-2-methyladamantane and cis- and trans-1-bromo-4-methyladamantane the expected products of bridgehead substitution, bromination of 2-methyladamantane with hot bromine gives 4eq- and 4ax-bromo-2-(dibromomethylene)adamantane. The monobromides were not isolated as such, but were hydrolysed to the corresponding alcohols. The tribromides may be formed by an ionic mechanism involving an adamantane–protoadamantane–adamantane rearrangement.