New convenient four-component synthesis of 6-amino-2,4-dihydropyrano[2,3-c]pyrazol-5-carbonitriles and one-pot synthesis of 6'-aminospiro[(3H)-indol-3,4'-pyrano[2,3-c]pyrazol]-(1H)-2-on-5'-carbonitriles.

This report describes a new four-component synthesis of substituted and spiro-conjugated 6-amino-2H,4H-pyrano[2,3-c]pyrazol-5-carbonitriles directly from aromatic aldehydes or heterocyclic ketones, malononitrile, beta-ketoesters, and hydrazine hydrate. The method provides a convenient one-pot route toward divers 2,4-dihydropyrano[2,3-c]pyrazoles, whereas a modified one-step sequential protocol gives access to spiro[indoline-3,4'-pyrano[2,3-c]pyrazol]-2-ones.