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4384028 
Journal Article 
Catalytic oxidation of cyclic ethers to lactones over various titanosilicates 
Sasidharan, M; Bhaumik, A 
2011 
Yes 
Journal of Molecular Catalysis A: Chemical
ISSN: 1381-1169 
338 
1-2 
105-110 
WOS:000289388700013 
Various crystalline microporous metallosilicates have been used in the liquid phase catalytic oxidation of different cyclic ethers into their corresponding lactones in the presence of dilute aqueous H2O2 as oxidant. Among the various metallosilicates studied for the oxidation of tetrahydrofuran to gamma-butyrolactone, titanosilicates exhibited the best activity than the other metallosilicates such as chromium silicalite-1 (CrS-1), chromium silicalite-2 (CrS-2) and vanadium silicalite-1 (VS-1). The intrinsic activity of TS-1 was found to be marginally higher than the other titanosilicates. Cyclic ethers undergo alpha(C-H) oxidation to give the corresponding lactones; whereas open-chain ether produce carboxylic acids by initial alpha(C-H) bond oxidation to give ester as an intermediate product, which further undergoes cleavage of -O- linkage to give the final carboxylic acids. The conversion of substituted tetrahydrofuran is decreased with number of -CH3 groups at alpha- and/or beta-position. The lactone formation is hindered when both the alpha-positions are substituted with methyl substituents. Mechanistically, titanium hydroperoxo complex formed in the titanosilicate/H2O2/H2O system is believed to oxidize the alpha(C-H) bond of ethers producing the respective alpha-hydroxylated product, which undergoes further oxidation to give the lactones (for cyclic ethers) or carboxylic acids (for open-chain ethers). (C) 2011 Elsevier B.V. All rights reserved. 
TS-1; Ether oxidation; Lactones; Tetrahydrofuran; Liquid phase oxidation catalysis