Evaluation of the Synthesis of 1-(Pentafluorophenyl)-4,5-dihydro-1h-pyrazoles Using Green Metrics

1-(Pentafluorophenyl)-4,5-dihydro-1H-pyrazoles were synthesized from the cyclocondensation reactions of 4-alkoxy-1,1,1-trihalo-3-alken-2-ones (CX3C(O)CH=C(R1)OR, where X = F, Cl; R = Me, Et; R1 = H, Me, Et, n-Pr, i-Pr, n-Bu, i-Pent, Ph, 4-Cl-C6H4, 4-Br-C6H4, 4-F-C6H4) with pentafluorophenyl hydrazine. Pyrazoles were obtained under microwave irradiation in solvent-free conditions or under conventional heating in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4]. These procedures furnished products in moderate to good yields in a short reaction time. Atom economy, reaction mass efficiency (RME), and environmental factor (E-factor) were determined for the cyclocondensation reaction performed under microwave (MW)/solvent-free and under conventional thermal heating/[BMIM][BF4] conditions. RME and E-factor indicated that the solvent-free procedure is invariably less green than [BMIM][BF4] when the isolated product was considered.