Recyclization of Condensed Carbethoxypyrimidines Accompanied by Substitution of a Carbon Atom into the Heterocycle.

Abstract

Fused pyrimidine derivatives R 0515 Recyclization of Condensed Carbethoxypyrimidines Accompanied by Substitution of a Carbon Atom into the Heterocycle. -6-Ethoxycarbonyl-7-methylazolopyrimidines (III) rearrange into 6-acetyl-7-hydroxyazolopyrimidines (IV) in alcoholic alkali solutions. Prolonged heating of pyrazolopyrimidine (IVb) in H2O/EtOH solution of KOH affords unexpectedly 7-methylpyrazolopyrimidine (V). Plausible rearrangement pathways are discussed. -(DANAGULYAN, G. G.; MKRTCHYAN, A. D.; PANOSYAN, G. A.; Chem. Heterocycl.

Kost-Sagitullin Rearrangement and Other Isomerization Recyclizations of Pyrimidines. (Review)

“…However, when 6-ethoxycarbonyl-7-methyl-2-phenylpyrazolo[1,5-a]pyrimidine (78) was boiled for 20 h with a 15% water-alcohol solution of potassium hydroxide, 7-methyl-2-phenylpyrazolo[1,5-a]pyrimidine (84) and not the expected Kost-Sagitullin rearrangement product was formed. An attempt at rearrangement of the 6-acetyl derivative 81 under the same conditions also did not lead to the corresponding Kost-Sagitullin recyclization product; the only isolated substance was the same pyrazolo-[1,5-a]pyrimidine 84 [120,121]. The formation of one and the same compound 84 in the two reactions can probably be explained by the occurrence of a series of successive recyclization transformations, including opening of the pyrimidine ring, its cyclization, and decarboxylation.…”

“…C-C Recyclization was observed in the condensed pyrimidine series; 6-ethoxycarbonyl-7-methylazolo[1,5-a]pyrimidines 78-80 were transformed after a few minutes into the corresponding 6-acetyl-7-hydroxy derivatives 81-83 (with yields of 58-67%) even at room temperature [119,120]. The scheme of such a transformation is presented below.…”