THE MONOMETHYL AND DIMETHYL DERIVATIVES OF BENZOPYRENE

Article abstract of DOI:10.1016/S0040-4020(01)98957-4

Convenient syntheses of the previously unknown complete set of six isomeric monomethyl derivatives of benzopyrene, 1-, 2-, 3-, 4-, 9- and 10-methylbenzopyrene, are described.Syntheses of 1-, 2- and 3-methylbenzopyrene were accomplished through reaction of 7H-benzanthrene (or its 1-Me derivative as appropriate) with 1,3-bis(dimethylamino)trimethinium perchlorate (or its 1-Me derivative) followed by thermal electrocyclic ring closure accompanied by elimination and aromatization.The earlier claim that the analogous isomeric benzopyrene derivatives are principal products of reactions of this type is disproven.Synthesis of 3,6- and 4,5-dimethylbenzopyrene are also described.The structural assignments of all mono- and dimethylbenzopyrene products are supported by high resolution 270 MHz proton NMR spectra; the chemical shifts and coupling constants of all aromatic protons are fully assigned.