Experimental and theoretical studies on physicochemical properties of novel six-membered cyclic α-monocarbonyl azo-compounds
Abstract
The preparation and physicochemical properties of a novel six-membered α-monocarbonyl azo-compound are reported. Low-temperature oxidation of 4,4-diaryl-3,4-dihydrophthalazin-1(2H)-ones (2) with lead tetra-acetate (LTA) in the presence of triethylamine in, CH2Cl2 afforded 4,4-diarylphthalazin-1(4H)-ones (3). Molecular orbital (MO) calculations on the model compound (8) of (3) disclosed on comparison with the corresponding azo-compound (7) and the αα′-dicarbonyl azo-compound (9) that the FMO properties of (8) are markedly different from that of (9). Thus, (8) should be a poor dienophile unlike (9), and analyses of the bond population indicated that (8) would undergo ready nitrogen extrusion as well as (7) and indeed, (3) was stable only below –60 °C. The MO calculations also indicated inherent 1,2-migration of the 4-substituent to the N(3) atom. 1,2-Aryl migration of (3) in acidic CH2Cl2 solution results in the formation of 3,4-diaryl-1-oxidophthalazinium betaine derivatives (13).