Hypervalent Iodine in Synthesis: A Novel Two‐Step Procedure for the Synthesis of New Derivatives of 1H‐Imidazo[1,2‐b]‐pyrazole by the Cyclocondensation Between 5‐Amino‐4‐cyano‐3‐phenyl‐1H‐pyrazole and α‐Tosyloxyacetophenones or α‐Haloacetophenones

Abstract

A series of new 7‐cyano‐6‐phenyl‐2‐aryl‐1H‐imidazo[1,2‐b]pyrazoles (5) by the cyclocondensation reactions between 5‐amino‐4‐cyano‐3‐phenyl‐1H‐pyrazole (1) and α‐bromoacetophenones (3) or α‐tosyloxyacetophenones (2) obtained by the reactions of acetophenones with [hydroxy(tosyloxy)iodo]benzene (HTIB) have been synthesized in good yields, and the intermediates 5‐amino‐4‐cyano‐6‐phenyl‐1‐(aroylmethyl)pyrazoles (4) were isolated as a potent evidence for the regioselectivity. The syntheses of 4 and 5 have been achieved successfully through the procedure involving α‐tosyloxyacetophenones and some through the procedure involving α‐bromoacetophenones. When utilizing α‐tosyloxyacetophenones, the reactions were more eco‐friendly, the reaction time was significantly reduced, and the synthetic procedure was more convenient and easier to manipulate.

Keywords:

• 1H‐imidazo[1,2‐b]pyrazole
• cyclocondensation
• [hydroxy(tosyloxy)iodo]benzene (HTIB)
• synthesis

Acknowledgment

The authors are grateful to Natural Science Foundation of Shandong Province (No. Y2003B01) and the NSFC of China (No. 20172031) for financial assistance.