Cobalt-catalyzed [2+2+2] cycloaddition of phenylacetylene with 1,3-dienes for the synthesis of Vinyl-substituted 1,4-diphenylcyclohexa-1,3-dienes

The cobalt-catalyzed [2+2+2] cycloaddition of two alkynes and a 1,3-diene, utilizing either a dibromo[1,2-bis(diphenylphosphino)] benzene cobalt or a dibromobis(triphenylphosphino)cobalt complex, under reductive conditions gives vinyl-substituted cyclohexa-1,3-diene derivatives in acceptable yields. The oxidation of 5-methyl-1,4-diphenyl-5-vinylcyclohexa-1,3-diene by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone leads to a rearrangement resulting in a vinyl-terphenyl derivative.