Mechanistic and synthetic studies in organic photochemistry. XII. Photodecarboxylation of esters. Photolysis of .alpha.- and .beta.-naphthalenemethyl derivatives
By using a charcoal supported nano Cu0 catalyst (Cu/C), a highly efficient oxidation of α-diazo esters to α-ketoesters with molecular oxygen as the sole oxidant has been developed. In the presence of the Cu/C catalyst, 2-aryl-α-diazo esters with both electron-donating and electron-withdrawing groups can be oxidized to the corresponding α-ketoesters efficiently. Furthermore, this Cu/C catalyst can catalyse
Rates of decarboxylation of acyloxy radicals formed in the photocleavage of substituted 1-naphthylmethyl alkanoates
作者:James W. Hilborn、James A. Pincock
DOI:10.1021/ja00007a049
日期:1991.3
Rates of decarboxylation (k(CO2)R) have been estimated for the acyloxy radicals 7a-f formed in the photolysis of substituted 1-naphthylmethyl alkanoates 6a-f. These rates are based on a proposed mechanism involving initial carbon-oxygen homolytic bond cleavage from the excited singlet state. The products are formed by two competing pathways: electron transfer in the radical pair to give an ion pair and decarboxylation. Measured product yields along with an estimate of the electron-transfer rate (k(ET)) allow calculation of k(CO2)R as a function of R. The values obtained are the following (R, k (10(9) s-1)): CH3, < 1.3; CH3CH2, 2.0; (CH3)2CH, 6.5; (CH3)3C, 11; PhCH2, 5.0; PhCH2CH2, 2.3.
Hilborn, James W.; Pincock, James A., Canadian Journal of Chemistry, 1992, vol. 70, # 3, p. 992 - 999