Synthesis and characterization of bromo‐, arylazo‐, and heterocyclic‐fused troponoids containing a 1,3‐benzodioxole system

Abstract

AbstractA facile synthesis of a series of novel bromo‐, arylazo‐, and heterocyclic fused troponoid compounds containing 1,3‐benzodioxole system is described. The 7‐bromo‐, 5,7‐dibromo‐, and 5‐arylazo‐substituted 3‐[(2E)‐3‐(1,3‐benzodioxol‐5‐yl)prop‐2‐enoyl]tropolones (2, 3, and 5, 6, 7) were obtained by direct bromination or azo‐coupling reactions of 3‐[(2E)‐3‐(1,3‐benzodioxol‐5‐yl)prop‐ 2‐enoyl]tropolone (1) with bromine, and diazonium salts of aniline derivatives, respectively. 3‐[(2E)‐3‐(1,3‐Benzodioxol‐5‐yl)prop‐2‐enoyl]‐5‐bromotropolone (4) was obtained from 3‐acetyl‐5‐bromotropolone via one‐pot aldol dehydration reaction with piperonal. Tropolones 2, 3, and 4 were subjected to nucleophilic cyclization with bifunctional hydroxylamine hydrochloride and phenylhydrazine hydrochloride to give the corresponding isoxazolo‐ and pyrazolo‐fused tropones (8, 9, 10, 11, 12, 13), respectively. J. Heterocyclic Chem., (2012).