The preparation and acid-catalysed rearrangement of a spiro epoxy alcohol in the benzo-fused norbornene series

Abstract

Epoxidation of 3-(1?-methylethylidene)-1,2,3,4-tetrahydro-1,4- methanonaphthalen-exo-2-ol (1) with meta-chloroperbenzoic acid formed exclusively the exo-epoxide (2). Acid-catalysed rearrangement of this spiro epoxy alcohol yielded two ring-expanded keto alcohols, exo-8- hydroxy-6,6-dimethyl-6,7,8,9-tetrahydro-5,9-methano-5H- benzocyclohepten-7-one (24) and exo-8-hydroxy-7,7-dimethyl-6,7,8,9- tetrahydro-5,9-methano-5H-benzocyclohepten-6-one (21), with the former predominating. Chemical and spectroscopic (including l.i.s.) methods were used to determine the structure of (21) and (24).