Syntheses of New Unsymmetrical 2,5-Disubstituted-1,3,4-oxadiazoles and 1,2,4-Triazolo3,4-b-1,3,4-thiadiazoles Bearing Thieno2,3-cpyrazolo Moiety

摘要

New series of (thieno2,3-cpyrazolo-5-yl)-1,2,4triazolo3,4-b1,3,4thiadiazoles 10a–c and (thieno2,3-c pyrazol-5-yl)-1,3,4-oxadiazol-3(2H)-yl)ethanones 6a–c has been synthesized from thieno2,3-cpyrazole-5- carbohydrazide 3 by multistep reaction sequence. (5-Aryl-1,3,4-oxadiazol-2-yl)-1H-thieno2,3-cpyrazoles 4a–c were also synthesized from thieno2,3-cpyrazole-5-carbohydrazide 3 by cyclization with various aromatic carboxylic acids. The hydrazide 3 was obtained by reaction of thieno2,3-cpyrazole-5-carboxylate 2 with hydrazine hydrate in good yield, and compound 2 was obtained by the reaction of 5-chloro-3-methyl-1-phenyl- 1H-pyrazole-4-carbaldehyde 1 and 2-ethyl thioglycolate in presence of sodium alcoholate in good yield.