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Communication | Regular issue | Vol 57, No. 4, 2002, pp.631-636
Published online, 1st January, 1970
DOI: 10.3987/COM-02-9450
The First Reliable, General Synthesis of the 5-Oxo Derivatives of 5,6-Dihydro-1,2,4-triazolo[4,3-c]pyrimidine and the Rates of Isomerization of the [4,3-c] Compounds into Their [1,5-c] Isomers

Tomohisa Nagamatsu* and Takayuki Fujita

*Faculty of Pharmaceutical Science, Okayama University, 1-1-1 Tsushima-naka, Okayama 700-8530, Japan

Abstract

This paper describes a reliable synthesis of the 5-oxo derivatives (8) of 5,6-dihydro-1,2,4-triazolo[4,3-c]pyrimidine, by the reaction of 2-oxo-1,2-dihydropyrimidin-4-ylhydrazines (7) with the appropriate triethyl orthoesters in trifluoroacetic acid below 30 °C or by the oxidative cyclization of their aldehyde hydrazones (10) with 70% nitric acid in trifluoroacetic acid below 40 °C, and the rates of isomerization of the [4,3-c] compounds (8) into the [1,5-c] isomers (9).