Ultrasound irradiation promotes the synthesis of new 1,2,4-triazolo[1,5-a]pyrimidine

• A series of 7-trifluoromethyl[aryl]-triazolo[1,5-a]pyrimidines under ultrasound irradiation was synthesized.
• Ultrasound irradiation method was more efficient than conventional thermal heating.
• Products were obtained with excellent yields.

Ultrasonic irradiation was used in the synthesis of a series of novel 1,2,4-triazolo[1,5-a]pyrimidines. The products were synthetized from the cyclocondensation reaction of 1,1,1-trifluoro-4-metoxy-3-alken-2-one [CF3C(O)CHC(R)OMe, where R = Ph, 4-F-C6H4, 4-Br-C6H4, 4-I-C6H4, 4-CH3-C6H4, 4-CH3O-C6H4, Thien-2-yl, Biphen-4-yl] or β-enaminones [RC(O)CHCHNMe2, where R = Ph, 4-F-C6H4, 4-Br-C6H4, 4-I-C6H4, 4-CH3-C6H4, 4-CH3O-C6H4, 4-NO2-C6H4, Thien-2-yl, Biphen-4-yl, Naphth-2-yl, Pyrrol-2-yl, CCl3] with 5-amino-1,2,4-triazole in acetic acid at 99 °C with 5–17 min of ultrasound irradiation. This methodology has shown several advantages, such as shorter reaction times, mild conditions, high regioselectivity, and excellent yields, when compared with conventional thermal heating (oil bath).