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Methyl 2-benzoylamino-2-oxobutanoate (1) was transformed with aromatic amines (2a-d) into methyl 2-arylamino-2-(benzoylamino)but-2-enoates (3a-d) Cyclization of compounds (3a-c) in polyphosphoric acid affords a mixture ofoxazolo[4,5-c]quinoline derivatives (4a-c) and 1 -aryl-2-phenyl-5-methyl- 1H-imidazole-4-carboxylates (5a-c), while compound 3d gives a mixture of 9-bromo- (4d) and 7-bromooxazolo[4,5-c]quinoline derivative (4d').

Coupling of 1-cyano-4-oxo-4H-quinolizine- (2), 1-ethoxycarbonyl-4-oxo-4H-quinolizine- (3), and 4-oxo-4H-pyridino[1,2-b]pyrimidine-3-diazonium tetrafluoroborates (4) with 1,3-dicarbonyl compounds (la-i) afforded the corresponding hydrazones (5-7) in 55-96% yields. The orientation around the C=N double bond in unsymmetrically substituted hydrazones (7a,c) was determined by NMR (NOESY) spectrometry. Heating of hydrazones (5a,b-7a,b), derived from alkyl 4-chloro-3-oxobutanoates (1a,b), furnished 1-(1-substituted quinolizin-3-yl)- (8, 9) and 1-(pyridino[1,2-a]-pyrimidin-3-yl)-4-hydroxy-1H-pyrazole-3-carboxylates (10) in 87-96% yields.

(Z)-3-Benzoylamino-4-dimethylamino-2-oxo-3-butene (4), prepared from 1-benzoylamino-2-propanone (3) and N,N-dimethylformamide dimethyl acetal, was converted regioselectively by reaction with a series of hydrazines (5) into 1-substituted 4-benzoylamino-5-methyl-1H-pyrazoles (8). Reactions of 4 with primary amines (10) and with dimethylbarbituric acid (12) afforded the dimethylamine substitution products (11) and (13), respectively. Treatment of the butenone (13) with ammonia furnished tetrahydropyrido[2,3-d]pyrimidine derivative (14).

5-(2-Phenyl-1H-indol-3-ylmethylene)-2-thioxoimidazolidin-4-one (2) and its oxo derivatives as well as some novel 5-bromoaplysinopsin analogues were synthesized employing dimethylamine substitution in N,N-dimethyl-methylideneimidazolidinones (6).