Reactivity of <i>p</i>‐phenyl substituted β‐enamino compounds using K‐10/ultrasound. <b>I</b>. Synthesis of pyrazoles and pyrazolinones

Abstract

Abstract The reactivity of the β‐enamino ketones, 3‐amino‐1‐( p ‐phenyl‐substituted)‐2‐buten‐1‐ones 1a‐d and β‐enamino esters, ethyl 3‐amino‐3‐( p ‐phenyl‐substituted)‐2‐propenoates 5a‐d was systematically studied when allowed to react with hydrazine and methylhydrazine under solid support K ‐10/ultrasound conditions and in homogeneous media (reflux in ethanol or dichloromethane). The products were pyrazoles 2a‐d , N ‐methylpyrazoles 3a‐d, 4a‐d and N‐methylpyrazolinones 6a‐c and 7a‐c . The regiochemistry of the cyclization reactions showed dependence upon the reaction conditions employed as well as upon the sub‐stituent in the aromatic ring.