In recent years, phosphorus acid tag is a valuable synthon due to its application at the preparation of catalysts, inhibitors, metal adsorbent and extractants [1]. Molecules with indole nucleus have attracted great interest due to the very important biological and pharmacologicalactivities, such as antibacterial, antifungal, antiviral, anticonvulsant, cardiovascular, optimal inhibitory, antihypertensive, anticholinergic and antiproliferative activities [2-3]. Pyridine moiety is one of the most important scaffolds which has found in the many pharmaceuticals and natural products due to their biological and medicinal properties such as inhibiting HIV protease, antidepressant, anti-inflammatory, inhibiting acetylcholinesterase, treating hypotension or hypertension [4]. Herein, we wish to develop vinylogous anomeric based oxidation mechanism at the preparation of (3´-indolyl)pyrazolo[3,4-b]pyridines from aryl aldehydes, 3-(1Hindol- 3-yl)-3-oxopropanenitrile and 3-methyl-1-phenyl-1H-pyrazol-5-amine in the presence of a catalytic amount of melamine hexakis(methylene)hexakis(phosphonic acid) [MHMHPA] under mild and green conditions
