Chiral Phosphinyl Enamines and Their Asymmetric Reduction through Group-Assisted Purification Chemistry Leading to Enantiopure β-Amino Esters/AmidesWe would like to acknowledge financial support from the National Natural Science Foundation of China (No. 21332005, 21672100) and the Robert Welch Foundation (D-1306).
Received: 11 May 2017
Accepted after revision: 26 June 2017
04 August 2017 (eFirst)
A series of new chiral N-phosphinyl β-enamino esters and amides were successfully prepared with excellent Z-stereoselectivity (Z/E > 99:1 in nearly all cases). Group-assisted purification chemistry proved to be an efficient method for the asymmetric reduction of the resulting β-enamino esters/amides to give enantiopure β-amino esters/amides. The asymmetric reduction can be controlled efficiently by using a combination of sodium cyanoborohydride and acetic acid.