REARRANGEMENT REACTIONS OF BICYCLIC SYSTEMS .5. ACID-CATALYZED REARRANGEMENTS OF 1,4-DIHYDRO-1,5,8-TRIMETHOXY-1,4-ETHENONAPHTHALENE AND THEREMARKABLE EFFECT OF AROMATIC METHOXY-GROUPS ON THE COURSE OF THE REACTION

3,6-Dimethoxyanthranilic acid (2) has been prepared by a procedure tha t is more reliable than our earlier one and used as a 3,6-dimerhoxyben zyne precursor in a reaction with anisole to give dihydro-1,5,8-trimet hoxy-1,4-ethenonaphthalenelene (1,5,8-trimethoxybenzobarrelene) (1). T rifluoroacetic acid-catalysed rearrangement of this benzobarrelene (1) gave as precedented products of bicyclo-rearrangement hydro-5,8-dimet hoxy-1,4-erhenonaphthalen-2(1H)-one (5,8-dimethoxybenzobarrelenone) (3 ) and 5,9-dihydro-1,4-dimethoxy-5 9-methanobenzocyclohepten-6-one (7) along with 2,4',5-trimethoxybiphenyl (6), the product of a remarkable retro-Friedel-Crafts protodealkoxyalkylative fragmentation of the bicy clic system. Similar reactions were observed with perchloric acid. The structure of this unexpected biphenyl was confirmed by its preparatio n by Gomberg-Bachman-Hey arylation of 1,4-dimethoxybenzene.