K2CO3-Mediated Regioselective Synthesis of Isoxazoles and Pyrazolines

3,5-Diarylisoxazoles and 1,3,5-triarylpyrazolines are synthesized via Michael addition of "hydroxylamine hydrochloride, phenylhydrazine" respectively over chalcones followed by cyclization using K2CO3 as solid support. Reactions are shown to be highly regioselective regardless of the nature of the substituent in the substrates and afforded single isoxazole and pyrazoline isomer in excellent yields.