A Rapid and Convenient Synthesis of Naphthyridinoyl Pyrazolidinones under Microwave Irradiation Condition

Microwave-assisted synthesis of naphthyridinoylpyrazolidinones (7a-7j) has been achieved rapidly via the reaction of naphthyridine hydrazide (4) with different β-keto esters and ethoxymethylenemalonic ester (EMME) (5a-5e). Initially, the reaction of naphthyridine hydrazide (4) with various β-keto esters under microwave irradiation for 5 mins at 130oC results in the formation of condensed products 6a-6j. This condensation was followed by cyclization, also, in diphenyl ether under microwave irradiation for 10 mins at 230-250oC, yielding the corresponding cyclized products 7a-7j. Alternatively, both reactants 4 and each of the β -keto esters/EMME (5a-5e) were treated in diphenyl ether under microwave irradiation for 15 mins at 230-250oC giving the target molecules 7a-7j as one-pot reaction in good yields.