Total Synthesis of (±)-α-Chamigrene and Brominated Chamigrene

Abstract

α-Chamigrene (1) and a bromochamigrene derivative, 9-(Z)-bromomethylidene-1, 5, 5-trimethylspiro [5, 5] undeca-1, 7-dien-3-one (2a) were synthesized via a useful synthon in the synthesis of chamigrene-type sesquiterpenes, i.e., 1, 5, 5-trimethylspiro [5, 5] undeca-7, 10-dien-3-one (5), which had been obtained by the copper (II) chloride-catalyzed decomposition of the phenolic α-diazoketone 4.