Benzocyclo-octenes. Part III. Reactions of 5,10-dibromobenzocyclo-octene

Abstract

The thermal decomposition of 5,10-dibromobenzocyclo-octene gives biphenylene and 2-bromobiphenylene. Reactions of this dihalide with silver salts also give 2-substituted biphenylenes, whereas reaction with sodium methoxide gives 1-methoxybiphenylene as the main product. The mechanisms of these reactions are discussed. The dihalide undergoes normal halogen–metal exchange to give 5,10-dilithiobenzocyclo-octene, thus providing routes to the parent hydrocarbon and other 5,10-disubstituted benzocyclo-octenes.