One-drop organocatalyzed multicomponent synthesis of pyrazolo[1,2-b]phthalazine-diones and pyrazolophthalazinyl quinolines

The catalytic potential of organocatalyst N-methylimidazole is explored in the multicomponent reactions of aromatic aldehydes, malononitrile and 2,3-dihydro-phthalazine-1,4-dione/5-amino-2,3-dihydro-phthalazine-1,4-dione for the synthesis of pyrazolo[1,2-b]phthalazine-diones in ethanol under reflux conditions. The protocol has been successfully extended for the synthesis of pyrazolophthalazinyl quinolines using one-pot three-component reactions of 2-chloro-3-formylquinoline, malononitrile/ethyl cyanoacetate and 2,3-dihydro-phthalazine-1,4-dione/5-nitro-2,3-dihydro-phthalazine-1,4-dione. The reported method describes a straightforward and highly efficient protocol with remarkable advantages, including wide substrate scope, ready availability, lower cost of catalyst, operational simplicity and good to high isolated yields along with in-flask catalyst recycling.