Green metal-free synthesis of spiro-fused 3,4′-pyrazolo[4′,3′:5,6]pyrido[2,3-d]pyrimidine derivatives via deamination cyclization reactions in aqueous medium

A green metal-free synthesis of spiro-fused 3,4′-pyrazolo[4′,3′:5,6]pyrido[2,3-d]pyrimidine derivatives via deamination cyclization reactions of isatins, substituted 1H-pyrazol-5-amine, and 6-aminopyrimidine-2,4(1H,3H)-dione or 6-amino-1,3-dimethylpyrimidine-2,4(1H,3H)-dione in aqueous medium is reported. This is an efficient route for synthesis of the target products by deamination cyclization reaction. The other advantages of this process are high yield, easy separation, wide substrate range, and environmental friendliness.