Acid Assisted Reactions of 1,2-Dihydro-2-(4,5-dihydroimidazol-2-yl)phthalazin-1-ol with Aryl(Heteroaryl) Methyl Ketones

A series of the 1-[2-(4,5-dihydro-1H-imidazol-2-yl)-1,2-dihydrophthalazin-1-yl]-2-arylethanone hydrochlorides (2a-i) was synthesized by acid assisted reaction of phthalazine pseudobase (1) with aryl(heteroaryl) methyl ketones.A similar reactions of 1 with cyclohexanone and benzo-1,4-dioxan-2-one afforded 1, 2, 3, 4, 6, 7, 15b, 15c-octahydro-4aH 6), respectively.Structures of these compounds were confirmed by IR and NMR spectroscopy as well as X-Ray crystallographic analysis of the free base (3a).Biological activity of the compounds (2) was examined on rabbit aortic rings.C 19 H 19 N 4 OCl 235-239 ethanol 67 2.58-2.65 (dd, J=13.6 Hz, J=12.0 Hz,1H, CH), 3.09-3.18(dd, J=13.6 Hz, J=3.3 Hz, 1H, CH), 3.28-3.71(m, 4H, 2CH 2 ), 5.43-5.50(dd, J=12.0 Hz, J=3.3 Hz, 1H, CH), 7.41-7.70(m, 10H, Ar, NH), 8.25 (s, 1H, CH=N), 9.62 (s, 1H, NH + )