Friedel-Crafts alkylation of pyrene in carbon disulfide; 1H NMR spectroscopy of pyrene derivatives

Article abstract of DOI:10.1002/recl.19881070903

Friedel-Crafts alkylation of pyrene with 2,5-dichloro-2,5-dimethylhexane and 2,4-dichloro-2,4-dimethylpentane in carbon disulfide yields 7,7,10,10-tetramethyl-7,8,9,10-tetrahydrobenzopyrene and 7,7,9,9-tetramethyl-8,9-dihydro-7H-cyclopentapyrene, respectively, both in 99percent yield.Alkylation with 1,4-dichlorobutane, followed by aromatization, yields benzopyrene in a facile two-step synthesis in 8percent yield.A mechanism is proposed which rationalizes the fact that only one ring of pyrene undergoes substitution.The 1H-1H NMR coupling constants of the pyrene derivatives are discussed.