Ionic‐Liquid‐Catalyzed Synthesis of Imines, Benzimidazoles, Benzothiazoles, Quinoxalines and Quinolines through C−N, C−S, and C−C Bond Formation

Abstract

We report the tetramethyl ammonium hydroxide catalyzed oxidative coupling of amines and alcohols for the synthesis of imines under metal‐free conditions by utilizing oxygen from air as the terminal oxidant. Under the same conditions, with ortho‐phenylene diamines and 2‐aminobenzenethiols the corresponding benzimidazoles and benzothiazoles were obtained. Quinoxalines were obtained from ortho‐phenylene diamines and 1‐phenylethane‐1,2‐diol, the conditions were then extended to the synthesis of quinoline building blocks by reaction of 2‐amino benzyl alcohols either with 1‐phenylethan‐1‐ol or acetophenone derivatives. The formation of C−N, C−S and C−C bonds was achieved under metal‐free conditions. A broad range of amines (aromatic, aliphatic, cyclic and heteroaromatic) as well as benzylic alcohols including heteroaryl alcohols reacted smoothly and provided the desired products. The mild reaction conditions, commercially available catalyst, metal‐free, good functional‐group tolerance, broad range of products (imines, benzimidazoles, benzothiazoles, quinoxalines and quinolines) and applicability at gram scale reactions are the advantages of the present strategy.