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Benzene rings of N-alkyltoluidine and benzene (or iodobenzene) in acetic acid were annelated with acetylenedicarboxylates by palladium(II) acetate to give N-alkylindole-2,3-dicarboxylate and naphthalene-1,2,3,4-tetracarboxylate. The formation of the products are explained in terms of toluidine radical cation intermediates.
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Sakakibara et al. (1986) studied this question.
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