An improved synthesis of benzocycloalkanone derivatives

A convenient and improved annulation method for the synthesis of bicyclic ketones was developed. A 2,2-dimethyl-6-(2-phenylsulfonyl)ethylcyclohexanone was converted into a sulfonylester by the addition of ethyl acetate and subsequent dehydration. A Dieckmann type condensation of the sulfonylester followed by desulfonylation afforded the 8,8-dimethyl-1,2,3,4,5,6,7,8-octahydronaphthalene-2-one in good yield. This annulation method was also applicable for the synthesis of the benzocyclooctanone derivative.