Modified Ta/MCM-41 catalysts for enantioselective oxidation of thioanisole

Abstract

Please cite this article as: Marwa Fadhli, Ilyes Khedher, José M.Fraile, Modified Ta/MCM-41 catalysts for enantioselective oxidation of thioanisole, Journal of Molecular Catalysis A: Chemical http://dx.Abstract 3 Highlights-Ta has been grafted on MCM41 and modified with chiral tartrates.-Ta catalyst are active in the oxidation of thioanisole.-They are more efficient with H 2 O 2 than with alkyl hydroperoxides.-Best results are obtained with diisopropyl tartrate (up to 25% ee).-Catalysts are recyclable with respect to activity but without enantioselectivity. 4 Abstract Ta-MCM41 catalysts have been prepared by grafting of Ta(OEt) 5 on MCM41, pre-calcined at three different temperatures (550, 650 and 750°C). These solids have been modified with two chiral ligands: R-(+)-diethyl L-tartrate (DET) and R-(+)-diisopropyl L-tartrate (DIPT). The formation of the chiral tantalum species and their influence on the structure of MCM41 have been studied by several characterization techniques, such as XRD, FTIR, N 2 adsorption isotherms and MAS-NMR. The grafted tantalum species are always much less active than the homogeneous analogues in the oxidation of thioanisole (methyl phenyl sulfide) with either aqueous H 2 O 2 or alkyl (tert-butyl, TBHP, or cumyl, CHP) hydroperoxides. The enantioselectivities obtained with the heterogeneous catalysts are also always lower than those obtained with the homogeneous ones under the same conditions, and the best results are obtained with the DIPT-modified solids, up to 25% ee. The calcination temperature of the support and the nature of the oxidant are also parameters that significantly affect the enantioselectivity. The recovered catalysts show an increase in the catalytic activity and a decrease in the enantioselectivity, in agreement with a loss of chiral tartrate, whereas the Si-O-Ta bond remains stable and recoverable.

Synthesis and characterization of dimeric μ‐oxidovanadium complexes as the functional model of vanadium bromoperoxidase

“…Therefore, the catalytic efficiency of synthesized catalysts, PS‐[V V O 2 (Haeae‐sal)] ( 5 ) and PS‐[V V O 2 (Haeae‐hyap)] ( 6 ), was evaluated for the oxidation of thioanisole. Sulfone and sulfoxide were identified as two major products (shown in scheme ) for this reaction which are well reported in the literature …”

Highly Selective Oxidation of Organic Sulfides by a Conjugated Polymer as the Photosensitizer for Singlet Oxygen Generation

“…HPLC analysis of the reaction solution with 3:7 (v/v) H 2 O/CH 3 CN eluent found two peaks at 3.45 and 6.55 min (Figure S2c in the Supporting Information), which represent methyl phenyl sulfoxide and thioanisole, respectively. No detection of the methyl phenyl sulfone by-product indicates the high selectivity of the reaction and confirms 1 O 2 as a more selective oxidizing agent than other oxidants like cumyl hydroperoxide, tert-butyl hydroperoxide, or H 2 O 2 . , The product at different reaction times is quantified using a standard plot of methyl phenyl sulfoxide in HPLC (Figure b).…”

“…No detection of the methyl phenyl sulfone by-product indicates the high selectivity of the reaction and confirms 1 O 2 as a more selective oxidizing agent than other oxidants like cumyl hydroperoxide, tert-butyl hydroperoxide, or H 2 O 2 . 25,28 The product at different reaction times is quantified using a standard plot of methyl phenyl sulfoxide in HPLC (Figure 1b).…”

Recent Advances in Tetra- (Ti, Sn, Zr, Hf) and Pentavalent (Nb, V, Ta) Metal-Substituted Molecular Sieve Catalysis

“…Group IV.B and V.B metal-substituted molecular sieves can catalyze different oxidation reactions, including hydroxylation of aromatics, oxidation of alcohols to ketones , and carboxylic acids, oxidation of organic sulfides to suplhoxides and sulphones, − and cyclohexanone ammoxidation . From mechanistic and catalyst performance standpoints, these reactions are similar to epoxidation because they all involve oxidant activation on metal sites.…”