Abstract
beta-ketoesters namely, ethyl acetoacetate (1a) or ethyl benzoylacetate (1b) reacted with 1,3-binucleophilic reagents to yield 1,2,3,6-tetrahydropyridine-3-carbonitrile (3a-d) derivatives. Each of 3a,b coupled with a proper arenediazonium or heteroarenediazonium salts to produce 5-aryl-(heteroaryl) azo-6-hydroxy-4-methyl-2-oxo(thioxo)-2,3-dihydropyridine-3-carbonitriles 5a-f. Heating under reflux each of 5c,e with acetic anhydride in pyridine led to cyclization and formation of pyrazolo[5,1-c] pyrido[2,3-e][1,2,4] triazine-3-carboxylate derivatives 6a,b. Compounds 3a, b added to 4-chloro-alpha-cyanocinammonitriles (7) in refluxing pyridine afforded pyrano[2,3-b] pyridines 8a,b. Treatment of 3b with bromomalononitrile in ethanolic potassium hydroxide solution gave directly 3-amino-8-cyano-7-methyl-5-oxothiazolo[3,2-a] pyridine-2-carboxamide(18). Heating compound 18 with either formic acid alone or in the presence of formamide yielded pyrido[2',3':2,3] thiazolo[4,5-d] pyrimidine derivatives 19,20 respectively.