Abstract
Condensation of thiazolinone 1 with benzaldehydes 2a,b in ethanolic piperidine afforded the methylidene derivatives 3ab. Cyclocondensation of compound 3b with malononitrile furnished the novel thiazolo[3,2-a]-pyridine 5. Also, compound 3b was condensed with dimethylformamide-dimethylacetal (DMF-DMA) and triethylorthoformate to yield N,N-dimethylamino 6 and ethoxmethylene 7 derivatives respectively. The novel thiazolo[3,2-a]pyridines 10a,b were obtained by cyclocondensation of compounds 3ab with benzylidene-malononitriles 8a,b. Similarly, cyclocondensation, of compound 3b with benzylidenemalononitrile 11 afforded the thiazolopyridines 12a-c. Ternary condensation of compound (12), 4-morpholinobenzaldehyde 2b and malononitrile (1:1:1 molar ratio) produced the thiazolopyridines 14a-c. When compound 10b was subjected to react with malononitrile in dioxane/piperidine under reflux the novel condensed heterocyclic system 18 was obtained. Treatment of ortho-aminocarbonitrile 10b with forinic acid, aromatic aldehyde and triethylorthoformate furnished the thiazolo[2',3':1,6] pyrido[2,3-d] pyrimidine 20, azonzethine 21a,b and ethoxymethylene 22 derivatives respectively. The structure of the synthesized compounds was established by analytical and spectral data.