A highly selective aerobic oxidation process catalyzed by electron-deficient nitroarenes via single electron transfer processes.
A versatile and simple method for aerobic oxidation of various aromatics containing an oxygen-functionalized benzylic carbon is reported. Results from oxidation experiments with methyl aryl ketones, benzaldehydes, benzylic alcohols, and mandelic acid are reported; all provide high yields of the corresponding aromatic carboxylic acids. By means of response surface methodology and mechanistic interpretation it is revealed that the oxidation process operates catalytically using electron-deficient nitroarenes, such as 1,3-dinitrobenzene, 1,2,3-trifluoro-4-nitrobenzene, and 2,4-difluoro-1-nitrobenzene, with molecular oxygen as the terminal oxidant. The reaction is carried out in a basic solution of potassium tert-butoxide in tert-butyl alcohol. Since the terminal oxidant is molecular oxygen and only 5-10 mol % of, e.g., 1,3-dinitrobenzene as catalyst is used, the new method represents an environmentally benign alternative to, for example, the well-known haloform reaction. The method is also a convincing alternative when transition metal free conditions are required.
Bjørsvik
Hans-René
HR
Department of Chemistry, University of Bergen, Allégaten 41, N-5007 Bergen, Norway. hans.bjorsvik@kj.uib.no
Liguori
Lucia
L
Vedia Merinero
José Angel
JA
D000332:Aerobiosis; D000438:Alcohols / Q000737:chemistry; D001547:Benzaldehydes / Q000737:chemistry; D002264:Carboxylic Acids / Q000138:chemical synthesis*; D004579:Electron Transport; D007659:Ketones / Q000737:chemistry*; D008333:Mandelic Acids / Q000737:chemistry; D010084:Oxidation-Reduction
D000438:Alcohols; D001547:Benzaldehydes; D002264:Carboxylic Acids; D007659:Ketones; D008333:Mandelic Acids; C037938:mandelic acid; C032175:benzaldehyde