Synthesis of amino derivatives of triazolopyrimidine

Reaction of 1-hetaryl-4-phenylthiosemicarbazides with N,N′-dicyclohexylcarbodiimide

“…In analogous reaction of thiosemicarbazide III with N,N′-dicyclohexylcarbodiimide in dioxane, the cyclization to form triazole ring involved both N 1 and N 3 in the pyrimidine ring, and the products were triazolopyrimidines IV and V which were isolated from the reaction mixture at a ratio of 5 : 1. These data differ from the results obtained with the use of methyl iodide and sodium acetate; in the latter case the cyclization regioselectively occurred only at the N 3 atom of the pyrimidine ring [2].…”

“…The 1 H NMR spectra were measured on a Varian VXR-300 spectrometer (300 MHz) in DMSO-d 6 using tetramethylsilane as internal reference. Compounds I [1], III [2], and VI and VIII [3] were reported previously. temperature 115-120°C).…”

“…We previously showed that heterocyclization of 1-(1,3-benzothiazol-2-yl)-4-phenylthiosemicarbazide with methyl iodide in ethanol in the presence of sodium acetate leads to the formation of 2,2′-dithiobis-[N-(3-methylsulfanyl-4-phenyl-1,2,4-triazol-5-yl)aniline] [1] and that 1-(4-methyl-6-oxo-1,6-dihydropyrimidin-2-yl)-4-arylthiosemicarbazides under analogous conditions are converted into 3-arylamino-7-methyl-5-oxo-1H-1,2,4-triazolo[4,3-a]pyrimidines [2]. 1-(4,6-Dimethylpyrimidin-2-yl)-4-arylthiosemicarbazides give rise to 2-arylamino-5,7-dimethyl-1,2,4-triazolo[1,5-a]-pyrimidines, and the reaction is accompanied by Dimroth rearrangement.…”

Imidazo(pyrimidine)annelated pyrido[3,2-d]pyrimidine. the synthesis and prediction of the biological activity / I.V.Dyachenko, R.I.Vaskevich, A.I.Vaskevich, M.V.Vovk

“…Ефективним підходом для досягнення цієї мети видається реакція електрофільної внутрі-шньомолекулярної циклізації (ЕВЦ), яка раніше була успішно опробована на 2-S-алкеніл(алкініл) функціоналізованих тієнопіримідинах [22,23], пі-разолопіримідинах [24][25][26], піридо [3,4-d]піримі-динах [27, 28] та птеридинах [29]. Імідазолідино-та піримідиноанелювання з використанням методу ЕВЦ було вдало продемонстровано на прикладах 2-N-алкеніл (алкініл)піразолопіримідинів [26] …”

Synthesis of arylamino-substituted pyrazolo[3,4-d][1,2,4]triazolo[4,3-a]pyrimidinones, pyrazolo[4,3-e][1,2,4]triazolo[4,3-a]pyrimidinones, and their thermal isomerization

“…In the presence of dicyclohexylcarbodiimide the cyclization was accompanied by the formation of unrearranged compounds, 3-arylamino-5,7-dimethyl-1,2,4-triazolo[1,5-a]-pyrimidines which further under alkaline conditions suffered the Dimroth rearrangement [2]. At the same time 1-(6-methyl-4-oxo-3,4-dihydropyrimidin-2-yl)-4-arylthiosemicarbazides in reactions with methyl iodide and sodium acetate provided 3-arylamino-7-methyl-5-oxo-1-hydro-1,2,4-triazolo[4,3-a]pyrimidines which did not suffer the catalytic Dimroth rearrangement [1].Aiming at a deeper understanding of the cyclization regiochemistry of 1-hetaryl-4-arylthiosemicarbazides under the action of methyl iodide and dicyclohexylcarbodiimide we tested 1-(4-oxo-1-R-5H-pyrazolo[3,4-d]-pyrimidin-6-yl)-4-arylthiosemicarbazides IIIa-IIIc, IVaIVc obtained from the corresponding 6-hydrazino-substituted pyrazolopyrimidines I and II (see the scheme). In compounds IIIa-IIIc, IVa-IVc the pyrimidine ring is fused with a pyrazole cycle providing a possibility to vary the substituent at N 1 atom and also to study the effect of the π-excessive pyrazole ring on the regiochemistry of the triazole ring formation.…”