beta-aminoenones in the regioselective synthesis of 1,3,5-trialkylpyrazoles. The influence of the substituents in the mechanism and the regioselectivity of the reaction

beta-Aminoenones react with monoalkyl hydrazines to give regioselectively 1 ,3,5-trisubstituted pyrazoles. The mechanism and level of regioselectivity depend on both the substitution pattern of the substrates and the reaction conditions. When the least bulky substituent is attached at the beta-positi on of the enone, a high regioselectivity is obtained, usually higher than t hat from equivalent beta-diketones. If the beta-substituent is the bulkiest group, the regioselectivity decreases. Nevertheless, in the conditions rep orted in this paper, it is possible to prepare pyrazoles not obtainable fro m beta-diketones.