I -0x0y -2 -xanthen y 1 but yric Acid into 2,3 -Benxoxanthone .By A. M. EL-ABBADY, S. AYOUB, and F. G. BADDAR.y-Oxo-y-2-xanthenylbutyric acid has been reduced to y-Z-xanthenylbutyric acid and then cyclised to 1',2',3',4'-tetrahydro-4'-0~0-2,3-benzoxanthen. This is reduced to 1',2',3',4'-tetrahydro-2,3-benzoxanthen, then dehydrogenated, and oxidised to 2,3-benzoxanthone. y-2-Xanthenylbutyric ester has been condensed with diethyl oxalate, and the oxalyl derivative cyclised to 1',2'-dihydro-Z,3-benzoxanthen-3',4'-dicarboxylic anhydride. This on dehydrogenation, decarboxylation, and oxidation gives 2,3-benzoxanthone.CONTRARY to a report by Burtner and Brown1 the Friedel-Crafts reaction of xanthen with succinic anhydride in benzene gave a mixture of y-oxo-y-2-xanthenylbutyric acid (I) and p-benzoylpropionic acid. However, condensation in acetylene tetrachloride afforded the keto-acid (I) in 96% yield. The structure of this keto-acid was established by its oxidation to xanthone-2-carboxylic acid (XIII) . Mild oxidation of either y-oxo-y-2xanthenylbutyric acid (I) or its methyl ester by potassium permanganate in aqueous acetone yielded y-oxo-y-2-xanthonylbutyric acid (11; R = H) or its methyl ester respectively. Hydrolysis of the diketo-ester (11; R = Me) with 5% alcoholic potassium hydroxide gave the diketo-acid (11; R = H), but treatment with 10% aqueous sodium hydroxide led to a phenolic acid. This was probably due to the rupture of the heterocyclic ring, to give ~-(4-hydroxy-3-o-hydroxybenzoylbenzoyl)propionic acid (111). Its structure was based on the fact that it cyclised back to the original ester (11; R = Me) on attempted methylation with methyl sulphate and potassium carbonate in acetone. A similar result was obtained with 2,Z'-dihydroxybenzophenone, which was converted into xanthone on attempted methylation with alkaline methyl sulphate 3a or on evaporation of its alkaline solution.36The structure of the acid (111) was further supported by its infrared spectrum. It showed a broad band a t 3200-3125 and a weak sharp band a t 3545 cm.-l (in CHClJ, characteristic for the chelated and the free OH group, respective1y.b Two bands a t 1695 and 1639 cm.-l (in Nujol) are characteristic for the side chain and the o-hydroxycarbonyl group, respectively.& Reduction of y-oxoy-2-xanthenylbutyric acid (I) by Clemmensen's method, or less satisfactorily by the Wolff-Kishner method, gave y-2-xanthenylbutyric acid (IV; R = H).Conversion of the acid (V; R = H) into 2,3-benzoxanthone (XIV) was carried out by two routes: ( A ) The acid chloride of (IV; R = H) was best cyclised with anhydrous stannic chloride, affording a cyclic ketone, theoretically of structure (VII) or (XV). It was proved