Pyrazole, 5-amino-3,4-dicyano-2-

Pyrazole, 5-amino-3,4-dicyano-l -methyl- "CNMR, 5, 191 <75JOC1815)... 

A new efficient procedure has been proposed for the synthesis of 3-aryl-5-amino-l//-pyrazoles by reaction of a-chloro-/ -arylacrylonitriles with hydrazine hydrate <2004RJ01518>. Reaction of 2-(3,3-dicyano-2-propenylidene)-4,4,5,5-tetra-methyl-l,3-dioxolane 641 with hydrazine afforded 3-(2-hydroxy-l,l,2-trimethylpropoxy)pyrazole 642 (Equation 134) <2003RJ01016>. Treatment of ethyl 3,3-dicyano-2-methoxyacrylate with alkyl, aryl, heterocyclic, and sulfonyl hydrazines led to the synthesis of N-l-substituted 3-acyM-cyano-5-aminopyrazoles, which are versatile intermediates for the synthesis of many biologically active scaffolds <2006TL5797>. 2-Hydrazinothiazol-4(5//)-one reacted with a variety of cinnamonitrile derivatives and activated acrylonitriles to yield annelated pyrazolopyrano[2,3-rf thiazole <1998JCM730>. 

Amino and dicyano- or cyanoethoxycarbonyl-ethylidene functions are annu-lated by heating with t-butoxide, TEA or acetic anhydride, or by stirring with methanolic sodium hydroxide. The 4-nitrophenyl derivative gave the highest yield, the 4-methoxyphenyl the lowest. Condensed pyrazoles have been reviewed [3902],... 

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