Straightforward microwave‐assisted synthesis of 1‐carboxymethyl‐5‐trifluoromethyl‐5‐hydroxy‐4,5‐dihydro‐1 H ‐pyrazoles under solvent‐free conditions

An efficient microwave‐assisted synthesis of 1‐carboxymethyl‐5‐trifluoromethyl‐5‐hydroxy‐4,5‐dihydro‐1 H ‐pyrazoles from the cyclocondensation reaction between enones [CF 3 C(O)C(R 2 ) = C(R 1 )(OR), where R 2 = H, Me; R 1 = H, Me, Et, Pr, i ‐Pr, t ‐Bu, i ‐Bu, Ph, 4‐NO 2 ‐Ph, 4‐Cl‐Ph, 4‐Br‐Ph, 4‐F‐Ph and R = Me, Et] and methyl hydrazinocarboxylate under solvent‐free conditions is reported. This process is an efficient alternative to the traditional thermal heating and furnishes the heterocyclic compounds in good to excellent yields in a short reaction time. To show the versatility of 1‐carboxymethyl‐5‐trifluoromethyl‐5‐hydroxy‐4,5‐dihydro‐1 H ‐pyrazoles, dehydration reactions of these compounds are also demonstrated. J. Heterocyclic Chem., (2010).