Alkene sulfoxide alkyl aryl

The photolytic cleavage of alkyl aryl sulfoxides has been shown to occur via initial C—S bond homolysis, in accordance with the common mechanistic assumption. Secondary and tertiary alkyl groups show high chemoselectivity for alkyl C—S cleavage. Uniquely, alkene products have been isolated, formed by disproportionation of the initial alkyl radical, with the formation of benzaldehyde and racemization of primary alkyl compounds. An investigation into the photochemical conversion of N-propylsulfobenzoic imides into amides in various solvents revealed a solvent dependence of the observed mechanism. In ethanol, sulfur dioxide extension forms a biradical which abstracts a hydrogen atom from the solvent, whereas in aromatic solvents biradical formation by a single electron transfer is implicated. The photolysis and thermolysis of l,9-bis(alkylthio)dibenzothiophenes and /7-aminophenyl disulfide have been studied. 

Finally, but certainly not least, we note that the enzyme chloroperoxidase (CPO), catalyzes the highly enantioselective (>98% ee) sulfoxidation of a range of substituted thioanisoles [308]. In contrast to the epoxidation of alkenes, where turnover frequencies were low (see above), in the case of sulfoxidation of thioa-nisole a turnover frequency of around 16 s-1 and a total turnover number of 125000 could be observed. A selection of data is represented in Fig. 4.112. Besides aryl alkyl sulfides, also dialkylsulfides could be oxidized with reasonable enantioselectivities [27]. 

The method employing the sequential alkylation and elimination of sulfoxides, reported above, has been successfully applied to the synthesis of dienes (Scheme 86, entry c), aryl alkenes and dienes (Scheme 47), vinyl sulfides, a,3-unsaturated sulfoxides, vinyl fluorides and vinyl chlorides (Scheme 96, entry a), and 1,1-dichloro-l-alkenes (Scheme 96, entry b). ... 

Sulfides, or thioethers, are sulfur analogues of ethers, and like ethers they can be either symmetrical (R2S) or unsymmetrical (RSR1, where R and R are different). Sulfides can be prepared from alkyl halides by a Williamson-type synthesis with sodium hydrogen sulfide, sodium thiolate or sodium sulfide from alkyl or aryl halides via the Grignard reagent (11) from alkenes by radical-catalysed addition of thiols or by reduction of sulfoxides (Scheme 9).2b... 

Other activated sulfoxides. This alkylative elimination reaction has been extended by Trost and Bridges to a one-pot synthesis of alkenes, vinyl sulfides, a, l-unsaturated sulfoxides, and a,j3-unsaturated nitriles. The sulfoxides (1-4) are converted into the anions by lithium N-isopropylcyclohexylamide or sodium hydride and are then alkylated at 20° in THE or DME elimination is then effected by raising the temperature to reflux. In some cases trimethyl phosphite is added as a scavenger for phenylsulfenic acid. Typical results are formulated in the equations. The elimination reaction is facilitated by an aryl, thioaryl, or... 

Asymmetric ene reaction of N-sulfinylcarbamatesf The ability of Lewis acids to promote ene reactions (11,413,414 12,389) is useful for asymmetric reactions. Thus the SnCU-promoted reaction of chiral N-sulfinylcarbamates (1) with alkenes results in thermally unstable adducts (2) in 65-91% yield. Use of trans-2-phenylcyclohexanol (13,244) or 8-phenylmenthol as the source of chirality results in high diastereoselective induction in generation of the new carbon to sulfur bond (usually >95 5). This reaction is applicable to both (E)- and (Z)-alkenes, but the former react more readily. These ene adducts can be transformed into optically active allylic alcohols (4) by N-alkylation and conversion to an aryl allylic sulfoxide (3), which undergoes rearrangement in the presence of a thiophile (piperidine) to 4, with retention of configuration at carbon imparted in the ene reaction. The overall process effects enantioselective allylic oxidation of an alkene with retention of the original position of the double bond. 

Mn catalysts that show activity in alkene or alcohol oxidation with H2O2 are potentially active in the oxidation of sulfides also. The Mn-tmtacn catalysts and a number of tn-sifu-formed complexes employing ligands such as 39 are examples of such catalysts (see above). These complexes were found to be highly active in the oxidation of sulfides to sulfoxides. For example, the dinudear manganese complex based on tmtacn (6) performs efficiently in the oxidation of aryl alkyl sulfides and generally results in fiJl conversion within 1 h. Unfortunately, as is often the case, in... 

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