Synthesis of α‐Propargylglycinates Using the Borono‐Mannich Reaction with Pinacol Allenylboronate and Potassium Allenyltrifluoroborate

Abstract

The three component borono‐Mannich reactions of ethyl glyoxylate, primary or secondary amines and pinacol allenylboronate or potassium allenyltrifluoroborate are highly regioselective and give α‐propargylglycinates. The ( S )‐ N ‐ tert ‐butylsulfinyl imine of ethyl glyoxylate underwent an indium chloride catalyzed addition reaction with allenyl potassium trifluoroborate in a highly regioselective and diastereoselective manner to give ethyl ( S )‐α‐propargylglycinate after N ‐deprotection in 97 % ee .