The Aza-ene Reaction of Heterocyclic Ketene Aminals with 4-Phenyl-1,2,4-triazoline-3,5-dione
作者:Jian-Heng Zhang、Mei-Xiang Wang、Zhi-Tang Huang
DOI:10.1039/a801566j
日期:——
Heterocyclicketeneaminals bearing a secondary enamine moiety underwent an efficient aza-ene reaction with 4-phenyl-1,2,4-triazoline-3,5-dione under very mild conditions, while no reaction was observed with their tertiary enamine analogues.
The stereoselective synthesis of O-galactosides of benzoyl-substituted heterocyclic ketene aminals was investigated. The benzoyl-substituted heterocyclic ketene aminals 1-4 reacted with 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide (5) in the presence of calcium hydride to give O-galactosides of benzoyl-substituted heterocyclic ketene aminals 6-9 with the Z-configuration. In comparison, 1-2 reacted with 5 in the presence of mercuric cyanide to give O-galactosides of benzoyl-substituted heterocyclic ketene aminals 10-11 with the E-configuration. Satisfactory results have been obtained in terms of both stereoselectivity and yield, and the beta-anomers are the sole products. (C) 1998 Elsevier Science Ltd. All rights reserved.