FORMATION OF POLYHETEROCYCLIC SYSTEMS BY REACTION OF 2-IMINO-4-METHYL-2H-1-BENZOPYRAN-3-CARBONITRILE WITH ACTIVE METHYLENE-COMPOUNDS

2-Imino-4-methyl-2H-1-benzopyran-3-carbonitrile undergoes [1,5] tautom erism in solution to mino-4-methylidene-4H-1-benzopyran-3-carbonitrile . Reaction with one equivalent of compounds containing a reactive meth ylene group affords simple 4-methylbenzopyran derivatives, and a methy lidene derivative (of [1] benzopyrano [2,3-b] [1,8] naphthyridine). Re action with two and three equivalents of malononitrile affords derivat ives of [1]benzopyrano[2,3,4-de]quinoline and [1]benzopyrano[2,3,4-de] [1,6]naphthyridine, which had previously been formulated as bicyclic benzopyran derivatives. The X-ray crystal structure of ethyl -imino-4- methyl-2H-1-benzopyran-3-yl)prop-2-enoate has been determined, showing the presence of two molecules in the asymmetric unit.