Facile synthesis of basic skeletons of naturally occurring lactonic terpenes

Abstract
Simple syntheses of the basic skeletons of some naturally occurring terpenes possessing lactone moieties are described. Thermolysis of 1,2-dihydro-6-methoxybenzocyclobuten-1-yl but-3-enoate (4) in a sealed tube at 180–200 °C afforded the cyclised lactone (5) in moderate yield. On similar treatment, the benzocyclobutenes (11) and (14) gave the corresponding fused lactones (12) and (15) respectively.