Regioselective synthesis and antibacterial evaluation of a new class of substituted pyrazolo[3,4-b]pyridines

New derivatives of polyfunctional pyrazolo[3,4-b] pyridines were synthesised via a regioselective one-pot three-component reaction of 3-(cyanoacetyl) indole, 5-amino-3-methylpyrazole and arylaldehydes in excellent yields using Fe3+-montmorillonite as a reusable catalyst under conventional conditions and ultrasonic irradiation. In particular, valuable features of this method include high reaction rate, employment of a reusable catalyst, straightforward procedure, the easy work-up of the products and mild reaction conditions. The antibacterial activities of the synthesised products were examined which showed promising activities.