Simplified Approach to the Regiospecific Synthesis of Trichloromethylpyrazolines Using Microwave Irradiation

Twelve novel 3-alkylaryl]-1-carboxamides-5-trichloromethyl-5-hydroxy-4,5-dihydro-lH-pyrazole have been synthesized in good yields (72–90%) using environmentally benign microwave-induced techniques. The compounds were synthesized from the cyclocondensation of 4-alkoxy-1,1,1-trichloro-3-alkylaryl]-2-ones Cl₃CC(O)C(R²) = C(R¹)OR, where R = Me, Et; R¹ = H, Me, Et, Pr, i-Pr, i-Bu, t-Bu, Ph, Ph-4-NO₂, Ph-4-F, Ph-4-Cl, Ph-4-Br; and R² = H, Me] with semicarbazide hydrochloride in the presence of pyridine and using methanol/water (3:1 v/v) as the solvent. The advantages of using microwave irradiation, rather than a conventional method, were demonstrated.