α-aminoazoles in the Synthesis of heterocycles: V. Synthesis of azolo[1,5-a]pyrimidines from 2-ethoxyvinyl trifluoromethyl ketones and 2,2-diethoxyvinyl trifluoromethyl ketone

Fluorinated β-Diketo Phosphorus Ylides: Their Cyclocondensation with Amidines Affording 4-Trifluoromethyl- and 4-Perfluoroalkyl-Substituted Pyrimidines

“…Products 2a, 11 2b, 4b 2d, 11 2eA, 12 2eB, 13 2h, 14 3, 8 4b, 9 and 5a 10 Being two electrophilic centers in 1,3-positions, trifluoromethyl -diketo phosphorus ylides (1) can be undergo cyclization reactions with 1,3-binucleophilic agents of amidines to pyrimidines 2. There have been reports that these unsymmetrical 1,3-diketones react with water, alcohols, ethanethiol, pyrrolidine and hydrazines to give the adducts at the COCF 3 carbonyl.…”

Regioselective Synthesis of 5-(Trifluoromethyl)[1,2,4]triazolo[1,5-a]pyrimidines from β-Enamino Diketones

“…In previous studies with such substrates, a mixture of regioisomers and low-yielding products were usually obtained. [24][25][26] However, in this present study, we explored the synthetic versatility of trifluoromethyl -enamino diketones in the cyclocondensation reaction with 3-amino-1H-1,2,4-triazoles, in order to prepare a series of new 6-substituted 5-(trifluoromethyl) [1,2,4]triazolo [1,5-a]pyrimidines, which furnished both high yields and excellent regioselectivity.…”

“…Initially, a series of -enamino diketones was synthesized by the C-acylation reaction of -enaminones with trifluoroacetic anhydride in the presence of pyridine, in accordance with the method developed previously. 27 The reaction conditions first employed were in accordance with those of Chernyshev and co-workers 28 who prepared trifluoromethyl derivatives containing the triazolopyrimidine scaffold from the reaction of -keto esters with 1-substitut-ed 3,5-diamino [1,2,4]triazoles, using acetic acid and reflux for 24 hours. However, using these conditions for our model reaction, we observed the elimination of COCF 3 from 1a, before attack of the aminoazole 2a (Scheme 3).…”

“…Having established the best conditions for the synthesis of 3a, we prepared a series of [1,2,4]triazolo[1,5-a]pyrimidines by reacting different -enamino diketones 1a-g with aminoazole 2a. The products were obtained in moderate (68%) to high (95%) yields; the isolated yields and structures are shown in Scheme 4.…”

“…Consequently, without the heating, the solubility of this specific aminotriazole was too low in all of the tested solvents, and only the starting materials were recovered. Given this result, we enhanced the reaction scope of the [1,2,4]triazolo [1,5-a]pyrimidines by reacting different enamino diketones 1a-d with aminotriazole 2b. The choice of the -enamino diketones used in this part of the study was based on the best isolated yields obtained for the compounds in Scheme 4.…”