Synthese von Benzylidenaminopyrazolen und Bispyrazolopyridinen

Abstract

Synthesis of Benzylideneaminopyrazoles and Bispyrazolopyridines 5‐Aminopyrazoles 1a – e react with aromatic aldehydes in boiling ethanol to yield azomethines 2a – n . Bispyrazolopyridines 7a – f are obtained by the reaction of 2a – f with an excess of aminopyrazole at higher temperatures via bisaminopyrazoles 5 and bispyrazolodihydropyridines 6 . Structure and configuration of the products are assigned by n.m.r.‐spectroscopy. Reactions with replacement of the arylidene group on azomethine 2b suggest that the transformation of azomethines to bisaminopyrazoles occurs through a mechanism involving addition of the CH‐acidic component, with subsequent elimination of aminopyrazole.