Cyclocondensation reactions of 5-aminopyrazoles, pyruvic acids and aldehydes. Multicomponent approaches to pyrazolopyridines and related products

The reactions of 3-substituted 5-aminopyrazoles with arylidenepyruvic acids and their synthetic precursors, pyruvic acid and aromatic aldehydes, were studied. Several different reaction pathways for these cyclocondensation reactions were established depending on the reaction conditions and building block selection. The formation of pyrazolo[3,4-b]pyridine-6-carboxylic acids as major products and related compounds was discussed from the mechanistic point of view.