Synthesis and Tautomeric Structure of 3,7-bis(arylazo)-2,6-dimethyl-1H-imidazo[1,2-b]pyrazoles

Abstract

Three series of 3,7-bis(arylazo)-2,6-dimethyl-1H-imidazo[1,2-b]pyrazoles were prepared starting from N-aryl-2-oxopropanehydrazonoyl chlorides. The acid dissociation constants pKa were determined and correlated with the Hammett equation. The results of such correlations together with the spectroscopic data indicated that the title compounds exist predominantly in the 1H-bis(arylazo) form.

Synthesis and Crystal Structures of 4,5-Dihydroimidazo[1,5-b]pyrazol-6-ones

“…5-Aminopyrazoles, the synthetic methods for which have been extensively reviewed, 11 are the main preparative intermediates for imidazo[1,2-b]pyrazoles. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] The synthesis and properties of imidazo [4,5-c]pyrazoles have also received considerable attention. [30][31][32][33][34][35][36][37][38][39][40][41][42] 5-Aminopyrazoles have also been of great utility in preparing these compounds.…”