A modified procedure was developed for the synthesis of 5,6,7,8,13,13a hexahydro phthalazino[1,2 b]quinazoline 5,8 dione and 6 amino 5,6,6a,11 tetrahydroisoindolo[2,1 a] quinazoline 5,11 dione from o formylbenzoic acid and anthranilic acid hydrazide. The mechanism of the transformation is suggested, some reactions were studied, and new derivatives of these compounds were synthesized. Anthranilic acid hydrazide was used in the novel synthesis of 5 substituted phthalazino[1,2 b]quinazolin 8 one derivatives. The possible reaction mechanism is discussed. 5,6,7,8 Tetrahydrophthalazino[1,2 b]quinazoline 5,8 dione and 5 phenylphthalazino[2,1 b]quinazolin 8 one were studied by X ray diffraction. Key words: anthranilic acid hydrazide, o formylbenzoic acid, o acetylbenzoic acid, o benzoylbenzoic acid, 5,6,7,8,13,13a hexahydrophthalazino[1,2 b]quinazoline 5,8 dione, 6 amino 5,6,6a,11 tetrahydroisoindolo[2,1 a]quinazoline 5,11 dione, phthalazino[1,2 b] quinazolin 8 one derivatives.It is known 1 that heating of anthranilic acid hydrazide (1) with o formylbenzoic acid (2) in dimethylacetamide affords a mixture of 5,6,7,8,13,13a hexahydrophthalazino [1,2 b]quinazoline 5,8 dione (3) and 6 amino 5,6,6a,11 tetrahydroisoindolo[2,1 a]quinazoline 5,11 dione (4). Biological assays showed that phthalazinoquinazoline 3, like many other compounds containing the -CO-N-Nstructural fragment, have analgesic properties, and some derivatives of 3 exhibit antiinflammatory activity. 2 In the present study, we report the modified proce dure for the synthesis of compounds 3 and 4, which does not require their additional separation. It was found that the reaction in butanol instead of dimethylacetamide pro ceeds analogously and gives the products in high yield, the reaction time decreasing from 3 to 1 h (Scheme 1).Compound 3 is insoluble in boiling butanol, as opposed to dimethylacetamide, 1 and precipitates from this solvent in an analytically pure form. After separation of compound 3, compound 4 crystallizes from the cooled filtrate also in a nearly pure state. The identical results obtained in different solvents, such as aprotic bipolar dimethylacetamide and protic butanol, show that the solvation does not play a significant role in the interaction under consideration. Moreover, the reaction under Scheme 1 i. Δ, 1 h, Bu n OH.
