Abstract
β-ketoesters namely, ethyl acetoacetate (1a) or ethyl benzoylacetate (1b) reacted with1,3-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-α-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.
Call for Papers in Thematic Issues
Catalytic C-H bond activation as a tool for functionalization of heterocycles
The major topic is the functionalization of heterocycles through catalyzed C-H bond activation. The strategies based on C-H activation not only provide straightforward formation of C-C or C-X bonds but, more importantly, allow for the avoidance of pre-functionalization of one or two of the cross-coupling partners. The beneficial impact of ...read more
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