ChemInform Abstract: Synthesis and Characterization of Bromo-, Arylazo-, and Heterocyclic-Fused Troponoids Containing a 1,3-Benzodioxole System

A 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).