Pyrazolyldiazonium Salts in the Synthesis of 4-Amino-1,3'-bipyrazoles

An efficient protocol for the synthesis of fluorescent 4-amino-1,3 '-bipyrazoles, which are substituted at the positions N-1 ', C-4 ', C-3 and C-5, is described. By a two-step synthetic strategy, an initial azo coupling of ethyl cyanoacetate and various 1-alkylpyrazolyldiazonium chlorides gave substituted ethyl 2-cyano-2-(2-(pyrazol-3-yl)hydrazine-ylidene)acetates, which were subsequently subjected to Thorpe-Ziegler type cyclisation reactions to yield the title compounds. Efficient syntheses of fluorescent, highly functionalized 4-amino-1,3 '-bipyrazoles from pyrazolyldiazonium salts via 2-(2-(pyrazol-3-yl)hydrazine-ylidene)acetates, which were subsequently subjected to Thorpe-Ziegler type cyclisation reactions, are described.image

Automated summary

An efficient protocol for the synthesis of fluorescent 4-amino-1,3'-bipyrazoles, which are highly functionalized, is described. The synthesis involves a two-step strategy, which includes an azo coupling reaction followed by a cyclisation reaction.