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Synthesis of 1,2,4-Triazolo[4,3-a]pyrimidine Derivatives by Cyclocondensation of a 2-Thioxopyrimidin-4(3H)-one with Hydrazonoyl Halides

✍ Scribed by Nehal M. Elwan; Enas M. Awad; Hamdi M. Hassaneen; Anthony Linden; Heinz Heimgartner

Publisher
John Wiley and Sons
Year
2003
Tongue
German
Weight
115 KB
Volume
86
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

The reaction of 1,2‐dihydro‐6‐(phenylamino)‐2‐thioxopyrimidin‐4(3__H__)one (16) with N‐arylhydrazonoyl halides 15 in CHCl~3~ in the presence of Et~3~N under reflux afforded the corresponding 1,2,4‐triazolo[4,3‐a]pyrimidin‐5‐ones of type 20 in good yields (Scheme 3). The structure of one of the derivatives, 20d, has been established by X‐ray crystallography. Conceivable reaction mechanisms are discussed in Schemes 3 and 4. The products of type 20 easily undergo reactions with electrophiles such as benzenediazonium chloride, chloroacetyl chloride, and NaNO~2~ in AcOH to give 6‐phenylazo, 6‐chloroacetyl, and 6‐nitroso derivatives 21, 23, and 25, respectively (Scheme 5).

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## Abstract A series of novel 1‐phenylthieno[1,2,4]triazolo[4,3‐__a__]pyrimidin‐5(4__H__)‐one derivatives **5** and **6** were synthesized by oxidative cyclization of thienopyrimidinonyl hydrazones using iodobenzene diacetate. J. Heterocyclic Chem., (2011).