Simplified approach to the regiospecific synthesis of trichloromethylpyrazolines using microwave irradiation

Twelve novel 3-alkyl[aryl]-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- alkyl[aryl]-2-ones [Cl3CC(O)C(R-2)=C(R-1)OR, where R=Me, Et; R-1=H, Me, Et, Pr, i-Pr, i-Bu, t-Bu, Ph, Ph-4-NO2, Ph-4-F, Ph-4-Cl, Ph-4-Br; and R-2=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.