An efficient synthesis of novel isoxazole bearing pyrazole derivatives via [3 + 2] heteroannulation using cupric acetate

Abstract

The synthesis of novel 3‐(4,5‐dichloro‐2‐fluorophenyl)‐1‐phenyl‐4‐(3‐phenylisoxazol‐5‐yl)‐1H‐pyrazole(7a–p) has been achieved via [3 + 2] heteroannulation reaction 3‐(3‐[4,5‐dichloro‐2‐fluorophenyl]‐1‐phenyl‐1H‐pyrazol‐4‐yl)‐1‐phenylprop‐2‐en‐1‐one(6a–p) and hydroxylamine hydro chloride using cupric acetate as homogenous precatalyst. Pyrazole derivatives were prepared by using etidronic acid as catalyst followed by Vilsmeier‐Haack reaction. An efficient green synthesis of isoxazole derivatives bearing pyrazole ring has been demonstrated with excellent yields. Structures of novel isoxazole derivatives were confirmed by elemental analysis and 1H NMR, 13C NMR, Mass, IR spectral studies.