The resin-bound 5-monosubstituted cyclic malonic ester 3 was generated and reacted with an α–bromoketone to give the corresponding 5,5-disubstituted cyclic malonic ester resin (4). Subsequent reaction with hydrazine resulted in cyclisation with concomitant cleavage from the polymeric support to release the final products, 4,6-disubstituted 4,5-dihydro-3(2 H)-pyridazinones, in good yield and high purity.