Benzocyclo-octatetraenes. Part I. Bromo-derivatives formed in addition reactions of biphenylene

Abstract

The non-catalysed reaction of bromine with biphenylene gives 3,8-dibromobenzocyclo-octatetraene (I) and a stereoisomer (V) of 1,2,4a,8b-tetrabromo-1,2,4a,8b-tetrahydrobiphenylene as primary products. Further bromination of these gives 3,5,6,8-tetrabromo-trans-5,6-dihydrobenzocyclo-octatetraene (II) and two stereoisomers of 1,2,3,4,4a,8b-hexabromo-1,2,3,4,4a,8b-hexahydrobiphenylene, respectively. The manner of formation of these products is discussed. The preparation of 1-bromobiphenylene, used as a reference compound, is described.