Utilization of the Sterically Hindered Base, 4-Hydroxy-2,2,6,6-tetramethylpiperidine, as a Hydrogen Halide Acceptor

Over the years, methods have been developed for the preparation of quaternary ammonium compounds, which are important as organic intermediates, detergents, insecticides, bacteriostats, and drugs [1, 2]. The most common method for preparation of these compounds is by alkylation of tertiary amines [3, 4]. Primary and secondary amines have also been quaternized, albeit less frequently [3, 4], due to the harsh reaction conditions which are often required. In order to prepare quaternary ammonium compounds from primary amines, methods have been developed to minimize unwanted side reactions and to increase the yields [3, 4]. Since the reaction of a primary amine with an alkylating agent, such as, an alkyl halide, results in the formation of a hydrogen halide, various amine hydrohalide salts will be formed as by-products, thereby complicating the reaction. In order to suppress the side reactions, various bases, such as sodium hydroxide [3], 2,6-lutidine [5], 1,6-lutidine [5], triethylamine [5], tri-w-butylamine [6], dicyclohexylamine [6], N,N-diethylaniline [6], N,N-di-w-