Ionic methylation of dichloro- and dibromoalkanes

The dichloro and dibromo derivatives of hydrocarbons are methylated by the action of tetramethylsilane in the presence of aluminum bromide with the formation of hydrocarbons containing a quaternary carbon atom, irrespective of whether the halogen atoms are at one or at different carbon atoms. The overall yield of the hydrocarbons during the methylation of dihalogenopentanes amounts to about 35% with a reaction time of 30 min. The optimum amount of aluminum bromide is a 1.5-fold excess on the halogen atom for compounds in which the halogen atoms are at primary carbon atoms and a threefold excess for compounds in which the halogen atoms are at secondary carbon atoms. Increase in the amount of aluminum bromide above the optimum and also increase in the reaction time do not lead to an increase in the yield of the methylation products.