Study toward the Mechanisms of Cyclohexanone Baeyer-Villiger Oxidation with hydrogen peroxide under Various Reaction Systems
China Petrol Proc & Petrochem Techn
2012, 14 (2):
The green and effective Baeyer-Villiger oxidation reaction of cyclohexanone to prepare ε-Caprolactone is of particular importance in the synthesis of new polymer materials. We have discussed here several mechanism types of cyclohexanone Baeyer-Villiger oxidation with H2O2 in different reaction systems. Five main types have been addressed. 1) Noncatalyzed reaction type, the C=O of ketones is activated by H+, which is electrolytic dissociated from H2O2 and H2O, to improve the capability of C=O group to accept the electron pairs;2）Thermally activated radical reaction type, where the Criegee interminate is produced via two-steps of radical reaction with ·OH attack, with many more hydroxy radicals are excited in the presence of TS-1 zeolite ;3) Br?nsted acid catalysis reaction type, both O-O moiety and C=O group could be activated by Br?nsted acid; 4) Solid Lewis acid catalyzed C=O of the substrate activation reaction type, by enhancing the donor-acceptor interaction between the antibonding π*C=O orbital of cyclohexanone and HOMO of Sn-β zeolite; 5) Solid Lewis acid catalyzed H2O2 to form Me-OOH oxidative species, by employing the highest occupied molecular orbital (HOMO) of Ti-OOH becoming a singly occupied molecular orbital(SOMO), with the O-O group highly electrophilic to attack the C=O of cyclohexanone in Baeyer-Villiger oxidation. In the end, we also compare the different mechanisms and give our opinions on the development direction of catalytic materials for eco-friendly Baeyer-Villiger oxidation of cyclohexanone in the years to come.
Related Articles |