A study on the mechanism and scope of the radical-mediated oxidation of arylacetoacetates

Abstract Arylacetoacetate la undergoes an oxidative degradation in the presence of K t BuO, THF, catalytic I 2 and O 2 , to give keto ester 4 as major compound. Hydrolysis and decarboxylation of this intermediate led to the corresponding arylcarboxylic acid 3a in satisfactory overall yields. By experiments conducted in the presence of 18 O 2 , incorporation of atmosphere oxygen into the benzylic position of 4 was evidenced. Furthermore, spin-trap experiments showed that benzyl radical 7 was generated in the reaction medium, which supports its role as intermediate in the pathway leading to the observed oxidation products. A plausible mechanism for this process is presented. On the other hand, appropriate conditions for achieving the alkylation of these arylacetoacetates with no concomitant formation of oxidation side-products are reported. Finally, arylacetates suffer also this degradative oxidation process leading to the corresponding arylcarboxylic acids without isolation of the intermediate keto ester derivative.