Studies on the impregnation step of the Merox process

7.28 Oxidation of Sulfur, Selenium, and Tellurium

“…455 Enantiomerically enriched allenic sulfones or cyclohexylidenemethyl ketones are obtained via asymmetric oxidation of the corresponding aryl vinyl selenides with the oxaziridine 137 or Ti/tartate system, followed by elimination in modest-to-good enantiocontrol (up to 83% ee). 456 Diastereoselective oxidation of an allylic selenide 141, bearing a tertiary amine as stereocontrol element, with MCPBA followed by [2,3]-sigmatropic rearrangement leads to allylic alcohol 142 in good yield and 66% ee (Scheme 71). 457 A similar approach has been reported by using the VO(aca) 2 /TBHP system.…”

“…Elimination of the selenoxide and telluroxide groups gives alkenes (see Volume 6, Chapter 6.18). The [2,3]-sigmatropic rearrangement of allylic sulfoxides and selenoxides affords the allylic alcohols (see Volume 6, Chapter 6.16).…”

“…Mechanistically, the oxidation of thiols to disulfides can proceed either via a radical (equation 3) or an ionic pathway (equation 4) (Scheme 2).…”

“…3 The oxidation of thiols to disulfides occurs easily, with an increasing rate from tertiary to primary alkyl derivatives and the aromatic thiols being the most reactive. The need to stop the process of oxidation selectively at the disulfide level without obtaining species at a higher oxidation state (compounds 6-10) has stimulated intensive research into selective methods in recent years.…”

Microwave assisted oxidative coupling of thiols to symmetrical disulfides with tripropylammonium fluorochromate(VI) (TPAFC)

“…Also, disulfides are key intermediates in a wide variety of organic synthetic routes [4][5][6]. Sweetening of catalyst poisoning thiols to disulfides of low volatility in the oil industry [7][8] and also the industrial applications of disulfides in the vulcanization of rubbers and elastomers led us to investigate a new reagent for the oxidation of thiols to the corresponding disulfides.…”