Advances in Formation of C—X Bonds via Cleavage of C—N Bond of Quaternary Ammonium Salts

Abstract

Amines have a wide variety and are readily available. Due to the larger C-N bond energy of amines, C-N bond of amines generally needs to be activated before cleavage. In recent years, a variety of activation methods of amino groups have been developed. Among the activation methods, converting amines into quaternary ammonium salts has certain advantages of easy preparation and stable storage. In last decade, quaternary ammonium salts derived from aromatic amines and benzylamines have made great progress in the study of constructing various C-X bonds via cleavage of C-N bond. This review mainly discusses the formation of C-X bonds of quaternary ammonium salts via cleavage of C-N bond with or without transition metal catalysts over the past few years. Via C-N bond breakage, quaternary ammonium salts can construct C-B bond, C-C bond, C-N bond, C-O bond, C-Si bond, C-P bond, C-S bond, C-Se bond, and so on. And thus borates, aromatics, alkanes, ethers, amines, silanes, phosphines, thioethers, disulfides, selenoethers, diselenides and other compounds are synthesized. Moreover, if the quaternary ammonium salts derived from chiral benzylamines are adopted, a variety of highly enantiopure chiral organic compounds are obtained. The chiralities of quaternary ammonium salts are excellently kept in the products, and S N 2 type configuration reversal occurs for all of the reported reactions. Keywords amines; quaternary ammonium salts; cleavage of C-N bond