Diaryl triketones

Diaryl triketones do not show the same reactivity as their dialkyl counterparts. This is illustrated by the fact that 19-hr irradiation through Pyrex using the full spectrum of a 1000-W, high-pressure, mercury-vapor lamp was required for 90% disappearance of 250 mg of diphenyl triketone (13) in degassed p-xylene solution. The major products isolated were p,p -dimethylbibenzyl, benzaldehyde, and p-methyl-benzyl phenyl ketone in addition, minor amounts of oxidation products such as p-methylbenzyl benzoate were identified, as well as traces of benzil. Quantum yields for the disappearance of 13 at 436 nm in degassed or air-saturated p-xylene solutions were about 3 x 10 k nearly identical values were obtained... 

Oxidation. DMSO in combination with catalytic amounts of iodine and a strong acid oxidizes methylene groups activated by an adjacent benzoyl group in good yield. The method is only suitable for preparation of diaryl di- and triketones. Examples ... 

When the triketones 256 was boiled with ammonia in ethanol, they afforded the respective hexahydroquinolines 257, but in individual cases additional oxidized products, tetrahydroquinolines 258 were formed (03CHE1121). Moreover, the triketone 256 (R3 = 4-N02-C6H4, R2 = H, R1 = Ph) gave upon treatment with ammonium acetate in glacial acetic acid at 150 °C, the tetrahydoquinolin-5-one 258. When the triketones 256 (R ,R3 = Ph or 4-MeO-C6H4) were reacted with excess hydroxylamine hydrochloride, the expected 2,4-diaryl-5,6,7,8-tetrahydroquinoline-5-oxime... 

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