Unsaturated sulfones epoxidation

Epoxidation of a, p-unsaturated sulfones. Epoxidation of cir-1-phenyl-2-(p-tolylsulfonyl)ethene (1) with alkaline hydrogen peroxide in aqueous acetone... 

The Julia-Colonna epoxidation uses poly-L-leucine and hydrogen peroxide to effect enantioselective epoxidation of chalconc derivatives such as 12. In a pair of back-to-back papers (Tetrahedron Lett. 2004,45, 5065 and 5069), H.-Christian Militzer of Bayer Healthcare AG, Wuppertal, reports a detailed optimization of this procedure. In the following paper (Tetrahedron Lett. 2004,45,5073), Stanley Roberts of the University of Liverpool reports the extension of this procedure to unsaturated sulfones such as 14. 

A very specific yet interesting epoxidation method for bicyclic a,(3-unsaturated sulfones has been reported <07SL1948>. Reaction of bicyclic sulfone 10 with A-methylmorpholine N-oxide (NMO) provides the epoxide product in generally good yields. Other amine oxides such as trimethylamine A-oxide work in this reaction, however non-strained sulfones do not react even with heating. 

From a historical perspective, the a-(dialkylamino)nitrile anions were the first acyl anion equivalents to undergo systematic investigation. More recent studies indicate that anions of a-(dialkylamino)nitriles derived from aliphatic, aromatic or heteroaromatic aldehydes intercept an array of electrophiles including alkyl halides, alkyl sulfonates, epoxides, aldehydes, ketones, acyl chlorides, chloroformates, unsaturated ketones, unsaturated esters and unsaturated nitriles. Aminonitriles are readily prepared and their anions are formed with a variety of bases such as sodium methoxide, KOH in alcohol, NaH, LDA, PhLi, sodium amide, 70% NaOH and potassium amide. Regeneration of the carbonyl group can be achieved... 

Epoxidation of Enones and a, 3-Unsaturated Sulfones Using Cinchona-Based Chiral Phase-Transfer Catalysts... 

The asymmetric phase-transfer epoxidation of ( )-a, 3-unsaturated sulfones has recently been achieved by Dorow and coworker using N-anthracenylmethyl cinchona alkaloid derivatives as catalysts and KOC1 as an oxidant at low temperature [23]. The screening of several etheral functional groups at the C9( O) position of the catalyst moiety indicated that the steric size and the electronic factor of the ether substituent has a significant effect on both the reaction conversion and the enantioselectivity. 

Catalyst 19, which contains the 3-fluorophenyl methyl ether, was found to be the most effective for the epoxidation of (fc)-a,P-unsaturated sulfones (Scheme 5.17). Of note, the (Z)-configured sulfone was converted under the same optimized conditions into the corresponding ds-a,P-cpoxysulfonc, but with a lower enantios-electivity (16% ee). 

Reaction conditions depend on the reactants and usually involve acid or base catalysis. Examples of X include sulfate, acid sulfate, alkane- or arenesulfonate, chloride, bromide, hydroxyl, alkoxide, perchlorate, etc. RX can also be an alkyl orthoformate or alkyl carboxylate. The reaction of cycHc alkylating agents, eg, epoxides and a2iridines, with sodium or potassium salts of alkyl hydroperoxides also promotes formation of dialkyl peroxides (44,66). Olefinic alkylating agents include acycHc and cycHc olefinic hydrocarbons, vinyl and isopropenyl ethers, enamines, A[-vinylamides, vinyl sulfonates, divinyl sulfone, and a, P-unsaturated compounds, eg, methyl acrylate, mesityl oxide, acrylamide, and acrylonitrile (44,66). 

Sulfitation and Bisulfitation of Unsaturated Hydrocarbons. Sulfites and bisulfites react with compounds such as olefins, epoxides, aldehydes, ketones, alkynes, a2iridines, and episulftdes to give aHphatic sulfonates or hydroxysulfonates. These compounds can be used as intermediates in the synthesis of a variety of organic compounds. 

Sulfonic peracids (66) have also been applied recently to the preparation of acid sensitive oxiranes and for the epoxidation of allylic and homoallylic alcohols, as well as relatively unreactive a, p - unsaturated ketones. These reagents, prepared in situ from the corresponding sulfonyl imidazolides 65, promote the same sense of diastereoselectivity as the conventional peracids, but often to a higher degree. In particular, the epoxidation of certain A -3-ketosteroids (e.g., 67) with sulfonic peracids 66 resulted in the formation of oxirane products (e.g., 68) in remarkably high diastereomeric excess. This increased selectivity is most likely the result of the considerable steric requirements about the sulfur atom, which enhances non-bonded interactions believed to be operative in the diastereoselection mechanism <96TET2957>. 

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