Abstract
Several new β-aminopyrroles, 3-aminoindoles, pyrido [3, 4-b] indoles, and pyrrolo-[3, 2-b] pyridines have been synthesized by a sequence of reactions involving intramolecular addition of an enamine to a cyano group. Enamine (1), prepared from tert-butyl aminocyanoacetate and cyclohexane-1, 3-dione, cyclized after substitution of the methine by ethyl bromoacetate in the presence of sodium ethoxide to afford 2-tert-butoxycarbonyl-2-ethoxycarbonylmethyl-3-imino-4-oxo-4, 5, 6, 7-tetrahydroindoline (2). Reaction of 1 with methyl vinyl ketone-sodium ethoxide furnished 3-amino-2-tert-butoxycarbonyl-4-oxo-4, 5, 6, 7-tetrahydroindole (7). Similarly, certain 3-aminopyrroles (44 and 45) and pyrrolo [3, 2-b] pyridines (51 and 52) have been synthesized from the enamine (41) prepared from acetoacetate and tert-butyl aminocyanoacetate. Enamines (70-72) obtained by condensation of ethyl acetoacetate with aminocyanoacetamides underwent cyclizations to 3-amino-2-carbamoylpyrroles (73-75) upon treatment with base. Several new 3-aminopyrroles thus prepared have been derived into new pyrrolo [3, 2-d]-(78-81) and pyrrolo-[3, 4-d] pyrimidines (90 and 91). A steric effect of the neighbouring butoxycarbonyl group in 41 has also been briefly discussed.
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