Highly Efficient System for Reduction of Carboxylic Acids and Their Derivatives to Alcohols by HfCl4/KBH4

Abstract HfCl4/KBH4 was found to be a facile, efficient, convenient, and chemoselective system for the reduction of carboxylic acids and their derivatives to the corresponding alcohols under mild conditions. HfCl4/NaBH4 was also utilized to reduce the same carboxylic acids and their derivatives, and it was found that the reducing ability of HfCl4/NaBH4 was similar to that of HfCl4/KBH4. The action of HfCl4/KBH4 on other types of substrates, such as benzyl chloride, peracid, epoxide, ketone, amide, imine, pyridine-N-oxide, and nitrile, was investigated, too. In addition, some competitive reductions of styrene oxide in the presence of carboxylic acid, carboxylic ester, nitrile, and amide were achieved.