Indoles, reaction with acetylenedicarboxylic acid

The purple charge-transfer complex of indole with tetracyanoethylene decomposes in neutral or basic media to the 3-substituted indole (164), whereas under acidic conditions the 2-(tricyanovinyl)-isoraer is formed. The cyclo-adducts of l-benzyl-3-vinylindole to tetracyanoethylene and maleic anhydride are the cyclobutane (165) and the tetrahydrocarbazole (166), respectivelyThe reaction of 9-methyl-l,2,3,4-tetrahydrocarbazole (167) with dimethyl acetylenedicarboxylate in aqueous acetic acid yields a mixture of the bridged compounds (168) and (169). The photo-adduct (170) of methyl acrylate to 1-benzoylindole rearranges to the benzazepine (171) in hot xylene... 

In the presence of a catalytic amount of concentrated hydrochloric acid, dimethyl 1 -methyl-1 H-l-benzazepine-3,4-dicarboxylate (1) undergoes addition of 1-methylindole, probably via initial protonation of the enaminic 3-position of the benzazepine ring, to give the indolyldihydrobenz-azepine 2.21 In fact, adduct 2 is the major product from the reaction of 1-mcthylindole with dimethyl acetylenedicarboxylate in acetonitrile. Similar adducts are obtained with indole. 

---