A facile one‐pot regioselective synthesis of [1,2,4]triazolo[4,3‐<i>a</i>]5(1<i>H</i>)‐pyrimidinones via tandem Japp–Klingemann, Smiles rearrangement, and cyclization reactions

Abstract

Abstract Coupling of active [(4‐oxo‐6‐phenyl‐3 H ‐pyrimidin‐2‐yl)thio]methine compounds ( 3 ) with diazotized anilines in the presence of base gave [1,2,4]triazolo[4,3‐a]pyrimidines ( 7 ). The latter products were also obtained by reactions of hydrazonoyl chlorides ( 10 ) with either 6‐phenyl‐2‐thiouracil ( 1 ) or the 2‐methylthio derivative 9 . The mechanisms and the regiochemistry of the reactions studied are discussed. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:136–140, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10008