Direct cycle between co-product and reactant: an approach to improve the atom economy and its application in the synthesis and protection of primary amines
Two important goals of green chemistry are to maximize the efficiency of reactants and to minimize the production of waste. In this study, a novel approach to improve the atom economy of a chemical process was developed by incorporating a direct cycle between a co-product and a reactant of the same reaction. To demonstrate this concept, recoverable 3,4-diphenylmaleic anhydride (1) was designed and used for the atom-economical synthesis of aliphatic primary amines from aqueous ammonia. In each individual cycle, only ammonia and alkyl halide were consumed, and 1 was recovered in nearly a quantitative yield. In this approach for developing atom-economical protecting agents, 1 showed good performance as a recoverable protecting agent for primary amines. The broad substrate scope, good tolerance to various reaction conditions, and high reaction and recovery rates make 1 a valuable complement to conventional primary amine protecting agents.