Synthesis of Methylated Benzofluoranthenes and Benzofluoranthenes

Article abstract of DOI:10.1021/jo00211a031

A series of monomethyl and dimethyl derivatives of benzofluoranthene (BbF) and benzofluoranthene (BkF) were synthesized in order to investigate the enviromental occurence and structural requirements for carcinogenicity of methylated nonalternant polycyclic aromatic hydrocarbons. 9-Methyl-BbF (5), 12-methyl-BbF (6), and 1-methyl-BbF (7) were prepared from the appropriate oxotetrahydro-BbF's (17-19). 8-Methyl-BbF (8) was synthesized from 1-methyl-3-oxo-1,2,3,10b-tetrahydrofluoranthene (20) in 11 steps. 3-Methyl-BbF (9) and 1,3-dimethyl-BbF (10) were prepared from 3-methyl-1-oxo-1,2,3,3a-tetrahydrobenzofluoranthene (31), which was synthesized from methyl 11H-benzofluorene-11-carboxylate (28). 7-Methyl-BbF (11) was obtained by condensation of 1-methylfluorene (33) with o-bromobenzaldehyde, followed by treatment with KOH and quinoline. 5,6-Dimethyl-BbF (12) was synthesized by reaction of 2,3-dimethylbutadiene with acephenanthrylene (38) followed by aromatization. 8-Methyl-BkF (13) was synthesized from 8-oxo-8,9,10,11-tetrahydro-BkF. 9-Methyl-BkF (14) was prepared by Friedel-Crafts reaction of 2-methylsuccinic anhydride with fluoranthene, followed by Wolff-Kishner reduction, cyclization, LiAlH4 reduction, dehydration, and aromatization. 2-Methyl-BkF (16) was synthesized by an analogous sequence, beginning with 2-methylfluoranthene and succinic anhydride. 7,12-Dimethyl-BkF (15) was prepared by a two-step reduction of 7,12-dicyano-BkF (51).