Microwave-assisted synthesis of novel 5-trichloromethyl-4,5-dihydro-1H-1-pyrazole methyl esters under solvent free conditions

Abstract

A preparação, com bons rendimentos (70–98%), de doze novos ésteres etílicos de 5-triclorometil-4,5-diidro-1H-1-pirazóis, usando-se ambientalmente boas técnicas induzidas por microondas, é descrita. Estes compostos foram sintetizados a partir da reação de ciclocondensação de 1,1,1-tricloro-4-alcoxi-3-alquen-2-onas [CCl3C(O)C(R2)=C(R1)OR, onde R, R2 = H, alquila; R1 = H, alquila e arila] com metil carboxilato hidrazina. As vantagens obtidas pelo uso de irradiações de microondas na ausência de solventes, em relação ao método convencional foram demonstradas.

Twelve novel 5-trichloromethyl-4,5-dihydro-1H-1-pyrazole ethyl esters have been synthesized in good yields (70–98%) by using environmentally benign microwave induced techniques. The compounds were synthesized from the cyclocondensation of 1,1,1-trichloro-4-alkoxy-3-alken-2-ones [CCl3C(O)C(R2)=C(R1)OR, where R, R2 = H, alkyl; R1 = H, alkyl andaryl] with hydrazine methyl carboxylate. The advantages obtained by the using of microwave irradiation under solvent-free conditions, rather than a conventional method, were demonstrated.