ENOLETHERS .20. SYNTHESIS OF AZEPINO[4,5-B]QUINOXALINES AND PYRIDOPYRAZINO[2,3-D]AZEPINES

1,6-Diethoxy-1,5-hexadiene-3,4-dione (1) reacts with primary amines 3 and ammonia respectively in a molar ratio of 1:1 to give mainly aminoa lkyl- and small amounts of bis(aminoalkyl)-1,5-hexadiene-3,4-diones 4 and 2, respectively. On heating in dichlorobenzene above 150-degrees t he mixtures of 2 and 4 cyclize to yield 1-alkyl-1H-azepine-4,5-diones 5 by elimination of ethanol or amine. 3H-3-Alkylazepino[4,5-b]-quinoxa lines 7, 8, 10 and 12 are easily accessible by condensation of the dik etones 5a and b with various substituted o-phenylenediamines 6, 9 and 3,3',4,4'-tetraaminobiphenyl (11) in p-xylene or n-butanol. 8-Iso-prop ylpyridopyrazino[2,3-d]azepines 14 were obtained by condensation of 5b with pyridinediamines 13 in p-xylene. The azepine-4,5-diones 5a-c can be hydrogenated selectively by sodium borohydride in ethanol at room temperature to give the azepin-4-ol-5-ones 15a-c.