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 alpha-tosyloxyacetophenones or alpha-haloacetophenones

A series of new 7-cyano-6-phenyl-2-aryl-IH-imidazo[1,2-b]pyrazoles (5) by the cyclocondensation reactions between 5-amino-4-cyano-3-phenyl-1H-pyrazole (1) and alpha-bromoacetophenones (3) or alpha-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-(aroylmethyi)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 alpha-tosyloxyacetophenones and some through the procedure involving alpha-bromoacetophenones. When utilizing a-tosyloxyacetophenones, the reactions were more eco-friendly, the reaction time was significantly reduced, and the synthetic procedure was more convenient and easier to manipulate.