An efficient protocol for synthesis of novel polyheterocyclic chromeno pyrimido[1,2-b]indazolone derivatives using [Et3NH][HSO4] as a reusable catalyst under solvent-free conditions

摘要

A convenient and highly efficient method for the synthesis of novel polyheterocyclic chromeno pyrimido [1,2-b]indazolone derivatives via a three-component condensation of 1H-indazol-3-amine, aldehydes and 4-hydroxycoumarin catalyzed by Bronsted acid ionic liquid [Et3NH]HSO4] under solvent-free reaction conditions is presented. This ionic liquid is air and water stable and easyto prepare from amine and acid. The main advantages of this protocol includes short reaction time, excellent yield, easy work-up, operational simplicity, a wide range of functional group tolerance and column chromatography-free method. The catalyst can be recovered and reused for at least four runs without any significant impact on the product yields. (C) 2019 Elsevier Ltd. All rights reserved.