Recent Advances in Synthesis of Benzazoles via Imines
Ran An, Mengbi Guo, Yingbo Zang, Hang Xu, Zhuang Hou, Chun Guo
Abstract
Imines, versatile intermediates for organic synthesis, can be exploited for the preparation of diverse classes of biologically active benzazoles. Because of the special characteristics of the C=N bond, imines can be simultaneously used in the synthesis of 1,3-benzazoles and 1,2-benzazoles. With the development of imine synthesis, a variety of novel cascade reactions for benzazole synthesis have been reported in the last decade. Therefore, there is a strong need to elucidate the recent progress in the formation of various classes of benzazoles, including benzimidazoles, benzoxazoles, benzothiazoles, indazoles, and benzisoxazoles, via imines obtained by condensation reactions or oxidative/ redox coupling reactions In this review, we provide a comprehensive survey of this area. In particular, various green and mild synthetic methodologies are summarized, and the multiple roles of novel catalysts and significant mechanisms for several transformations are highlighted in detail. We believe that this review will aid researchers studying the synthesis of complex molecules containing the benzazole motif via imines.