SYNTHESIS OF NOVEL BENZOFURO-FUSED THIAZOLO[3,2-a]-PYRIMIDINONES VIA PICTET-SPENGLER REACTION

摘要

An efficient method for the preparation of novel benzofuro[3',2':2,3]pyrido[4,5:d]thiazolo[3,2-a]pyrimidin-5-ones 5 is described. The key intermediate, 7-(3-amino-2-benzofuran)-5H-thiazolo[3,2-a]pyrimidin-5-one (3), was synthesized from 7-(chloromethyl)-5H-thiazolo[3,2-a]pyrimidin-5-one (1) with salicylonitrile (2) by Thorpe-Ziegler isomerization. Subsequent reaction of the intermediate amine with aromatic aldehydes via Pictet-Spengler reaction provided benzofuro-fused thiazolo[3,2-a]pyrimidines under sulfamic acid as catalyst in good yields.