Cu-Catalyzed Chemoselective Reduction of N-Heteroaromatics with NH3·BH3 in Aqueous Solution

Abstract

An efficient catalytic system was successfully developed on reduction of N-heteroaromatics with H3N∙BH3 as hydrogen source in CuSO4 solution, featuring excellent chemoselectivity as well as very broad functional group tolerance. Various challenging substrates, such as OH-, NH2-, Cl-, Br-, etc., contained quinolines, quinoxalines, 1,5-naphthyridines and quinazolines were all reduced smoothly. Mechanistic studies suggested that [Cu-H] intermediate might be generated from NH3∙BH3, which was believed to form with H3N∙BH3 in CuSO4 solution.