Transition metal-catalyzed construction of C-X bonds via cleavage of C-N bond of quaternary ammonium salts

Amines are abundant in natural product chemistry and are readily available chemical raw materials. The C-N bonds of amines are difficult to break due to the large C-N bond energy. In recent years, chemists have developed a variety of activation methods for amino groups of amines. Among these reported methods, to convert amines into quaternary ammonium salts is preferred, for quaternary ammonium salts are readily available and stable. In recent years, great progress has been achieved in the study of transition metal-catalyzed construction of various C-X bonds involving aromatic amines and benzyl amines-derived quaternary ammonium salts by cleavage of C-N bonds. This review describes the transition metal-catalyzed reaction of quaternary ammonium salts to construct C-X bonds by cleavage of C-N bond. Moreover, if chiral benzylamines-derived quaternary ammonium salts are used, a variety of highly enantiomeric pure chiral organic compounds can also be obtained. The chirality of quaternary ammonium salts remained good in the products and all reactions underwent SN2-type configuration inversion.