2-CHLORO-4,5-DIHYDROIMIDAZOLE .8. SYNTHESES OF NOVEL FUSED HETEROCYCLIC-SYSTEMS BY REACTIONS OF IHYDRO-2-(4,5-DIHYDROIMIDAZOL-2-YL)PHTHALAZIN-1-OL WITH ACTIVE METHYLENE-COMPOUNDS

Three-component reactions of 1 with pyridazine or phthalazine afforded the 1,2-dihydro derivatives 2a and 2b, respectively. A similar reacti on of 1 with phthalazine performed in aqueous NaOH led to the formatio n of pseudobase 3. The latter compound proved to be an excellent subst rate for the preparation of a series of novel 1,2-dihydrophthalazine d erivatives 4a-c, 5 as well as 6a-b by reactions with a variety of acti ve methylene compounds.