Controlled Reduction of Carboxamides to Alcohols or Amines by Zinc Hydrides

Abstract

New protocols for controlled reduction of carboxamides to either alcohols or amines were established using a combination of sodium hydride (NaH) and zinc halides (ZnX2 ). Use of a different halide on ZnX2 dictates the selectivity, wherein the NaH-ZnI2 system delivers alcohols and NaH-ZnCl2 gives amines. Extensive mechanistic studies by experimental and theoretical approaches imply that polymeric zinc hydride (ZnH2 )∞ is responsible for alcohol formation, whereas dimeric zinc chloride hydride (H-Zn-Cl)2 is the key species for the production of amines.Ministry of Education (MOE)Accepted versionThis work was supported by funding from Nanyang Technological University (NTU) (for S.C.), the Singapore Ministry of Education (Academic Research Fund Tier 1: RG10/17 for S.C.), and Takeda Science Foundation (for R.T.). Computations were performed using Research Center for Computational Science at Okazaki, Japan. We thank Prof. Subodh G. Mhaisalkar (School of Materials Science and Engineering, NTU) and Prof. Han Sen Soo (School of Physical and Mathematical Sciences, NTU) for the assistance in powder X‐ray diffraction (XRD) experiments