77746-54-4

A series of new 3-(N-1,3-diarylpyrazol-5-yl)amino-2H-[1,4]-benzoxa/ thiazines (4a-c, 5a & 6a-c) and 3-(N-1,3-diarylpyrazol-5-yl)iminomethyl chromones (8a-e) have been synthesized from 5-amino-1,3-diarylpyrazoles (1).

The Vilsmeier-Haack reaction of 5-aminopyrazole derivatives 1 was investigated in view of contradictory literature reports.Structure 2 of the products was proved both chemically and spectroscopically.The mechanism of the reaction was postulated on the basis of isolated intermediates 7 and 8. 5-Acylaminopyrazoles 9, 10 and 11 were found to give also 2 (and 7) under the Vilsmeier conditions by an acyl splitting reaction, proceeding probably via diacylamino derivatives 12.Compounds 2 provided a simple route to pyrazolopyrimidine derivatives 13 and 14 as well as to azomethine compounds 15-18.