Polymer-bound sulfoxides

NaHCOs, and methanesulfonic anhydride.Dimethyl sulfoxide in 48% HBr oxidizes benzylic alcohols the aryl aldehydes.Note that Swern oxidation of molecules having alcohol moieties, as well as a disulfide, leads to the ketone without oxidation of the sulfur. Sulfoxides other than DMSO can be used in conjunction with oxalyl chloride for the oxidation of alcohols,including fluorinated sulfoxides and a polymer-bound sulfoxide. ... 

Swern oxidations have been performed using the PEG2000 bound sulfoxide 34 as a dimethylsulfoxide (DMSO) substitute (reaction 13).49-50 Several alcohols were efficiently oxidized to their aldehydes or ketones using this reagent, oxalyl chloride, and triethylamine. Precipitation of the polymer with cold diethyl ether and filtration through a pad of silica afforded the desired oxidized products in very good yields and purities. The reduced sulfide polymer could be reoxidized to sulfoxide 34 with sodium metaperiodate and used again in reactions with no appreciable loss in oxidation capacity. 

Liu, Y. Vederas, J. C. Modification of the Swem Oxidation Use of Stoichiometric Amounts of an Easily Separable, Recyclable, and Odorless Sulfoxide That Can Be Polymer-Bound, J. Org. Chem. 1996, 61, 7856. 

The applications reported for polymer-supported, soluble oxidation catalysts are the use of poly(vinylbenzyl)trimethylammonium chloride for the autooxidation of 2,6-di-tert-butylphenol [8], of copper polyaniline nanocomposites for the Wacker oxidation reaction [9], of cationic polymers containing cobalt(II) phthalocyanate for the autooxidation of 2-mercaptoethanol [10] and oxidation of olefins [11], of polymer-bound phthalocyanines for oxidative decomposition of polychlorophenols [12], and of a norbornene-based polymer with polymer-fixed manganese(IV) complexes for the catalytic oxidation of alkanes [13], Noncatalytic processes can also be found, such as the use of soluble polystyrene-based sulfoxide reagents for Swern oxidation [14], The reactions listed above will be described in more detail in the following paragraphs. 

Sulfoxides. Sulfoxides such as DMSO have long been used as oxidizing agents. Release of the oxygen affords the offensively malodorous sulfide. A polymer-bound sulfide has been formed by the... 

The use of a sulfoxide in order to oxidize an alcohol requires the conversion of that alcohol into a leaving group. The use of a polymer-immobilized carbodlimide can permit this Moffat-type oxidation to proceed readily (39). In this work by Welnshenker and Shen, the oxidant is not polymer-bound. 

Generally, the activities of polymer-bound palladium catalysts are less than those of unsupported ones, but here too there are exceptions. Kaneda et al reported that PdCl2, on phosphinated polystyrene was more active than the homogeneous situation.Rates were very solvent dependent— hydrogenation of styrene was slow in dimethyl sulfoxide optimum activity was obtained in solvents of moderate coordinating ability (see Table 6). 

Determination of amino acid composition is, beyond doubt, the most informative method in the analysis of synthetic peptides. The preceding hydrolysis of peptide bonds must of course be complete. This can be achieved by dissolving the sample in constant boiling hydrochloric acid and heating of the solution, preferably in an evacuated and sealed ampoule, at 110°C for 16 hours. Some blocked intermediates, however, are insoluble in the ca 6 N HCl even at its boiling point. In such cases mixtures of HCl with formic acid or acetic acid can solve the problem. For the hydrolysis of polymer-bound peptides often an HCl-propionic acid mixture is applied. The presence of methionine sulfoxide in synthetic peptides deserves special consideration. On hydrolysis with HCl both methionine and its sulfoxide appear on the recordings of the amino acid analyzer, but not necessarily in the ratio they occur in the sample. The sulfoxide is partially reduced ... 

Modification of the Swem oxidation has also been achieved by the use of a soluble, polymer-bound, recyclable, and odorless sulfoxide 1873a [1394]. Sulfoxides bound... 

Organic hydroperoxides are generally used for the preparation of sulfoxides from sulfides, - while sulfones can be obtained in neutral organic solvents in the presence of metal catalysts such as V, Mo and Ti oxides at 50-70 C. Two polymer-supported reagents which involve peroxy acid groups and bound hypervalent vanadium(V) and molybdenum(VI) compounds have been developed for facile oxidation of sulfoxides to sulfones. 

Another kind of evidence for the involvement of ion radicals in photo-oxidation ccmies from the observation of cleavage of certain sulfides (41) with formation of unoxidized disulfides. Unlike the benzyl alkyl sulfides (40). di-t-butyl sulfide gives on oxidation with several photosensitizers, in addition to the sulfoxide and sulfone, amounts of di-t-butyl disulfide varying from traces with rose bengal or methylene blue in methanol to 97 and 100% in acetone with rose bengal free and bound on polymer beads, respectively. The yield of the disulfide may be a measure of the relative rate at which the cation radical 1 dissociated to the t-butyl cation and the t-butylthiyl radical in the various media ... 

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