A diastereo and chemo selective synthesis of 6-amino-4-aryl-3-oxo-2,3,3a,4-tetrahydro-1H-pyrazolo[3,4-b]pyridine-5-carbonitrile under environmentally benevolent conditions

Abstract

We have developed an environmentally friendly benign and practical protocol for the highly diastereo and chemo selective synthesis of some novel derivatives of 6-amino-4-aryl-3-oxo-2,3,3a,4-tetrahydro-1H-pyrazolo[3,4-b]pyridine-5-carbonitrile via a one-pot three-component reaction between arylaldehydes, malononitrile and 3-amino-1H-pyrazol-5(4H)-one in the presence of acetic acid as a catalyst and aqueous green medium at the ambient temperature. In this synthetic protocol, we highlight the utility of enaminone functional groups of 3-amino-1H-pyrazol-5(4H)-one for the synthesis of N-cyclized pyrazolone fused 3,4-dihydropyridine skeletons. Some important features of this new synthetic green strategy is the highly diastereoselective and chemoselective approach, easily available and inexpensive substrates, avoiding tedious work up, short reaction time, and quantitative yields. Furthermore, no metal catalysts, hazardous and volatile organic solvents, even in the purification state, are used in our procedure. Also, this synthetic protocol defined as GAP (Group-Assistant-Purification) chemistry process, can avoid traditional chromatography and crystallization.