Cyclizative Condensations. II. 2-Methylindole with Methyl Ketones

Monobases analogous to the 2:2 product from acetone (Ia) are formed by condensation of 2-methylindole with: (a) benzalacetone or its adduct with 2-methylindole (IIIa), leading to Ic; (b) methyl vinyl ketone or its adduct with 2-methyl-indole (IIIb), leading to Id; (c) 1-acetylcyclohexene, leading to the tetracyclic monobase V; and with (d) the adduct of indole and methyl vinyl ketone (IIIc), leading to Ie, which was aromatized to the carbazole VII. 1,2-Dimethylindole also condensed with the adduct of indole and methyl vinyl ketone (IIIc), leading to the monobase If. Attempted condensation of 2-methylindole with methyl isopropenyl ketone gave, not the monobase Ig, but 2,2′-dimethyl-3,3′-methylenebisindole (VIII), which was prepared independently from 2-methylindole and methyleneaminoacetonitrile. Condensation of 2-methylindole with methyl isobutyl ketone gave a monobasic 2:1 product of doubtful structure, possibly X, which forms an N (indoline)methyl derivative.