Regiospecific synthesis of 2,3,6,7,10,11-hexasubstituted triphenylenes by oxidative photocyclisation of 3,3″,4,4′,4″,5′-hexasubstituted 1,1′ : 2′1″-terphenyls

Photolysis of 4′,5′-dimethoxy-1,1′ : 2′,1″-terphenyl (3) in the presence of iodine gives 2,3-dimethoxy-triphenylene (4)(72%). A similar photolysis of either 3,4-dimethoxy-3″,4′,4″,5′-tetramethyl-1,1′ : 2′,1″-terphenyl (5)or 4′,5′-dimethoxy-3,3″4,4″-tetramethyl-1,1′ : 2′1″-terphenyl (7) gives 2,3-dimethoxy-6,7,10,11-tetramethyltriphenylene (6). The regiospecificity of these photocyclisation reactions makes this the best route to asymmetrical 2,3,6,7,10,11-hexasubstituted derivatives of triphenylene.