Methyl transfer in quaternary alkylammonium salts, derivatives of 1,4:3,6-dianhydrohexitols

An unexpected side-reaction took place during the synthesis of quaternary ammonium salts with O-triflyl derivatives of 1,4:3,6-dianhydrohexitols and tertiary alkylamines. The products were identified as tertiary amine derivatives of 1,4:3,6-dianhydrohexitol and tetraalkylammonium triflate. It was found that formation of the products was the consequence of the methyl group migration from QAS formed to the amine present in excess in the reaction mixture. Such reaction is a case of transquaternization, in which the exchange of the methyl group between two amines occurs. (C) 2020 The Authors. Published by Elsevier B.V.