Please login first
A Novel Ring Expansion of Pyrimidines to 1,2,4-Triazepines
, *
1  N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky Ave., 119991 Moscow, Russian Federation


A base-promoted ring expansion of 3-amino-4-hydroxyhexahydropyrimidine-2-thiones into 2,4,5,6-tetrahydro-3H-1,2,4-triazepine-3-thiones has been developed. Experimental data and DFT calculations showed that the reaction proceeded through fast formation of intermediate acyclic isomers of pyrimidines followed by their slow cyclization into triazepines. The starting hydroxypyrimidines were prepared by reaction of α,β-unsaturated ketones or β-alkoxy ketones with HNCS followed by treatment of the obtained β-isothiocyanato ketones with hydrazine.

Keywords: Isothiocyanato ketones; Thiosemicarbazides; Pyrimidines; Ring expansion; 1,2,4-Triazepines