Rivularins. Preliminary Synthetic Studies

Article abstract of DOI:10.1021/jo00183a015

The 3,4'-biindole system of rivularin D has been synthesized from 1-(2,2-dimethoxyethyl)-2-methyl-3-nitrobenzene by consecutive Batcho-Leimgruber and Fischer indolizations. 5-Bromo-3-(2-methyl-3-nitrophenyl)-1H-indole could be converted to 5-bromo-1-methyl-3,4'-bi-1H-indole or 10-bromo-7-methyl-7H-naphth<2,1-b>indol-4-amine by heating with N,N'-dimethylformamide dialkyl acetal, followed by reduction with Raney nickel/hydrazine.In contrast to the generally operative alkylation mechanism which involves the alkoxy groups of the intermediate alkoxyimminium ion derived from the N,N'-dialkylformamide dialkyl acetal, the N-methylation reactions presented here are shown to be unique examples where the N-methylation step is effected by the N-methyl groups of N,N'-dimethylformamide dimethyl acetal.