An Efficient and Facile Synthesis of Functionalized Indole‐3‐yl Pyrazole Derivatives Starting from 3‐Cyanoacetylindole

The versatile hitherto reported 3‐(1H‐indol‐3‐yl)‐1H‐pyrazol‐5‐amine ( 4 ) was synthesized by the reaction of 3‐cyanoacetylindole ( 3 ) with hydrazine hydrate in refluxing ethanol and used as a key intermediate for the synthesis of novel pyrazolo1,5‐a ]pyrimidines via its reactions with appropriate 1,3‐biselectrophilic reagents or through three‐component condensations with triethyl orthoformate and compounds possessing an activated methylene group. Besides, the applicability and synthetic potency of ( 4 ) to attain polyfunctionally substituted imidazo1,2‐b ]pyrazole, pyrazolo1,5‐a ]1,3]diazepine and pyrazolo1,5‐c ]1,3,5]thiadiazine derivatives of an expected pharmaceutical interest have been investigated. The mechanistic aspects for the formation of the newly synthesized compounds are discussed.