2005
Oxidation
O 0212
11- 061
Selective Oxidation of Aryl Ketones to α-Diketones with 4-Aminoperoxybenzoic
Acid Supported on Silica Gel in the Presence of Air. — A clean and high-yielding
preparation of α-diketones (II) is achieved by oxidation of α-methylene aryl ketones
(I) with the title reagent in the presence of air. The reaction remains incomplete in the
absence of air. No side products are observed. Oxidation of a benzylic methylene occurs
easier than that of a methylene α to a carbonyl group, cf. (III)→(IV). Partial oxidation
of cyclic ketones (V) and (VII) into lactones is observed. Aliphatic α-methylene ketones remain intact under these conditions. This procedure includes further advantages
like use of a nontoxic reagent, mild reaction conditions, high selectivity, easy work-up,
and reusability of the supported reagent. — (GHAZANFARI*, D.; NAJAFIZADEH,
F.; KHOSRAVI, F.; Monatsh. Chem. 135 (2004) 11, 1409-1413; Dep. Chem., Islamic
Azad Univ., Kerman, Iran; Eng.) — H. Hoennerscheid