Polycyclic biphenylenes. Part 6. Direct routes to benzo[b]biphenylene and related systems via cycloaddition reactions

Abstract

The simultaneous generation of 1,2-dibromobenzocyclobutene and 5,6-bis(bromomethylene)cyclohexa-1,3-diene gives benzo[b]biphenylene directly. Annelated derivatives of this ring system, including naphtho[2,3-b]-, biphenyleno[2,3-a]-, and biphenyleno[2,3-b]-biphenylenes may be obtained by variations of this procedure. Some cycloaddition reactions of 1,2-dibromobenzocyclobutene with cyclopenta-2,4-dienones and with thiophene 1,1-dioxides, giving rise to simple biphenylenes, are also described.