A Rapid, Convergent, and Regioselective Synthesis of Anthracenes

Article abstract of DOI:10.1021/jo00052a027

Anthracenes are obtained in moderate to good yield by the simultaneous treatment of benzocyclobutenols and halobenzenes with LTMP in tetrahydropyran.In the key step of this one-pot process, o-toluoyl anion intermediates from the known ring-opening of benzocyclobutenoxides add to halobenzene derived arynes.Methoxy-substituted benzocyclobutenols which are readily made regiospecifically by known methods also react regiospecifically with the single benzyne generated from either a 2- or 3-haloanisole.For example, the only trimethoxyanthracene isolated (48percent yield) from the reaction of 6-methoxybenzocyclobutenol (8) with 5-chloro-1,3-dimethoxybenzene is the 1,3,8-isomer 20.When 1,2-dihydrocyclobutaphenanthren-1-ol (14) and/or halonaphthalenes are the reactants, benzannulated anthracenes are formed; e.g., tribenzanthracene in 68percent yield from 14 and bromonaphthalene.In another extension, pentaphene (31) was made in one pot from o-dichlorobenzene.