Mara R. B. Marzari

Pyrazole synthesis under microwave irradiation and solvent-free conditions

This paper presents a study of solvent-free reaction conditions using microwave irradiation (MW) to obtain 4,5-dihydro-1H-pyrazoles and dehydrated pyrazoles by the cyclocondensation reaction of 4-alkoxy-1,1,1-trifluoro-3-alken-2-ones [CF3C(O)CH=C(R1)OR, where R/R1 = Et/H, Me/Me and Me/Ph] with hydrazines [NH2NH-R2, where R2 = CO2Me, Ph, CH2CH2OH]. Some reactions were performed under the same reaction conditions using methanol as solvent. The results obtained using MW equipment for synthesis under solvent-free conditions were also compared with those described in literature for conventional thermal heating and heating with a domestic MW oven. In general, the products furnished by reaction in MW equipment for synthesis presented better yields and shorter reaction times. In addition, it was demonstrated that the reaction temperature altered the formation of products for each hydrazine showing that MW equipment for synthesis is efficient for reacting hydrazines and 4-alkoxy-1,1,1-trifluoro-3-alken-2-ones to procedure the products 4,5-dihydro-1H-pyrazoles and dehydrated pyrazoles.

A solvent-free synthesis of beta-enamino trihalomethyl ketones

An efficient green procedure to prepare a series of twenty-six 4-amino-1,1,1-trihalo-3-alken-2-ones [CX3C(O)CH=C(R1)NR2 R3, where X = F, Cl, R1 = H, Me, and R2/R3 = H/Ph, H/4-F-Ph, H/Bn, H/(CH2)2OH, Me/Ph, Me/Bu, Et/Et, -(CH2)4-] from the solvent-free reaction of 1,1,1-trihalo-4-alkoxy-3-alken-2-ones with primary and secondary amines at room temperature for five minutes is reported (yields of 73-99%).

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

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).

Resourceful synthesis of pyrazolo[1,5-a]pyrimidines under ultrasound irradiation

Pyrazolo[1,5-a]pyrimidines were synthesized via the ultrasonic sonochemical method using the cyclocondensation reaction of 4-alkoxy-1,1,1-trifluoro-3-alken-2-ones [CF3C(O)CH=C(R)(OMe) - where R=Me, Bu, i-Bu, Ph, 4-Me-C6H4, 4-F-C6H4, 4-Cl-C6H4, 4-Br-C6H4, naphth-2-yl and biphen-4-yl] - with 3-amino-5-methyl-1H-pyrazole in the presence of EtOH for 5 min. This methodology has several advantages, for example, it is a simple procedure, it has an easy work-up, mild conditions, short reaction times (5 min) and produces satisfactory yields (61-98%).

Synthesis of novel quinolines using TsOH/ionic liquid under microwave

2 = Me, Et, Pr, Bu, i-Bu and i-Pe) and 2-aminoacetophenone. The reaction was performed in ionic liquid and 4-toluene sulfonic acid under microwave irradiation. Results showed that the catalytic method was effective. Products were formed in a short time (10-20 min) and presented good yields (70-91%).

2-Methyl-5-(4-tol-yl)-7-(trifluoro-meth-yl)pyrazolo[1,5-a]pyrimidine.

In the title compound, C15H12F3N3, the pyrazolo[1,5-a]pyrimidine system ring is essentially planar with a maximum deviation from the mean plane of 0.014 (1) Å. The 4-tolyl group makes a dihedral angle of 14.1 (1)° with the pyrazolo[1,5-a]pyrimidine ring system. The crystal packing is stabilized mainly by van der Waals forces.