Regioselective Three-Component Synthesis of Indolylpyrazolo[3,4-b]pyridines Induced by Microwave and under Solvent-Free Conditions

New 4-(1H-indol-3-yl)-6-arylpyrazolo[3,4-b] pyridines 7 have been prepared in a solvent-free three-component reaction induced by microwave from 5-aminopyrazole 1, benzaldehydes 2 and 3-indolyl-3-oxopropanenitrile 5. These compounds were also obtained by means of the reaction of aminopyrazole 1 with benzylidene-derivatives of 3-(1H-indol-3- yl)-3-oxopropanenitrile 6, prepared in the reaction of 3-(1H-indol-3-yl)-3-oxopropanenitrile and aldehydes.