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Synthesis of 1,2,4‐Triazolo[4,3‐ a ]pyrimidine Derivatives by Cyclocondensation of a 2‐Thioxopyrimidin‐4(3 H )‐one with Hydrazonoyl Halides
Author(s) -
Elwan Nehal M.,
Awad Enas M.,
Hassaneen Hamdi M.,
Linden Anthony,
Heimgartner Heinz
Publication year - 2003
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200390073
Subject(s) - chemistry , chloroacetyl chloride , halide , pyrimidine , medicinal chemistry , electrophile , chloride , organic chemistry , stereochemistry , catalysis
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 ).