Synthesis of Benzylidenaminopyrazoles 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.
Hennig, L.,Hofmann, J.,Alva-Astudillo, M.,Mann, G.
p. 351 - 358
(2007/10/02)
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