Chiral sulfoxides organic synthesis

It should be noted that the related imine-oxaziridine couple E-F finds application in asymmetric sulfoxidation, which is discussed in Section 10.3. Similarly, chiral oxoammonium ions G enable catalytic stereoselective oxidation of alcohols and thus, e.g., kinetic resolution of racemates. Processes of this type are discussed in Section 10.4. Whereas perhydrates, e.g. of fluorinated ketones, have several applications in oxidation catalysis [5], e.g. for the preparation of epoxides from olefins, it seems that no application of chiral perhydrates in asymmetric synthesis has yet been found. Metal-free oxidation catalysis - achiral or chiral - has, nevertheless, become a very potent method in organic synthesis, and the field is developing rapidly [6]. 

As a further stereoselective organic synthesis [40-47] using reactive sp2 carbon-centered radicals, eq. 10.23 shows the preparation of chiral 4-te/7-butylcyclohexene (49) from the optically pure o-bromophenyl sulfoxide (48) through 1,5-H shift by sp2 carbon-centered radical, followed by (3-elimination. This reaction looks like a thermal concerted intramolecular elimination reaction (Ei). 

Chiral Acetylenic Sulfoxides and Related Compounds in Organic Synthesis... 

The typical S-oxidation with BVMOs allows the formation of chiral sulfoxides from organic sulfides. This oxidation has received much interest in organic chemistry due to its use in the synthesis of enantiomerically enriched materials as chiral auxiliaries or directly as biologically active ingredients. This reaction has been studied extensively with CHMO from Adnetohacter showing high enantioselectivi-ties in the sulfoxidation of alkyl aryl sulfides, disulfides, dialkyl sulfides, and cychc and acyclic 1,3-dithioacetals [90]. CHMO also catalyzes the enantioselective oxida-hon of organic cyclic sulfites to sulfates [91]. 

Asymmetric sulfinyl transfer reactions are of significant interest, since they can be applied to the synthesis of chiral sulfur-containing compounds, which are valuable synthons for pharmaceuticals and natural products [46]. Moreover, chiral sulfoxides are versatile chiral auxiliaries for asymmetric organic synthesis. A number of studies... 

Lee AWM, Chan WH (1997) Chiral Acetylenic Sulfoxides and Related Compounds in Organic Synthesis. 190 103-129... 

Enantiomerically pure sulfoxides are important intermediates in organic synthesis (21) and quite a number of pharmaceuticals and other biologically active compounds harbor a chiral sulfoxide unit (22). With respect to oxidation catalysis, enantiomerically enriched sulfoxides can either be accessed by asymmetric sulfoxidation of prochiral thioethers (Scheme 7, path a), or by kinetic resolution of racemic sulfoxides (Scheme 7, path b). For the latter purpose, enantio-specific oxidation of one sulfoxide enantiomer to the sul-fone, followed by separation, is the method of choice. 

Feldman KS, Karatjas AG (2006) Extending Pummaer reaction chtanistry. Asymmetric synthesis of spirocyclic oxindoles via chiral mdole-2-sulfoxides. Organic Lett 8 4137-4140... 

The use of sulfoxides as chiral synthons has, over recent years, become a highly dependable protocol in synthetic organic chemistry. To some extent, however, the use of sulfoxides in asymmetric synthesis has been limited by the lack of a reliable and general method for their preparation in optically pure form. In this review we present the development of chiral sulfoxide synthesis via nucleophilic displacement at sulfur from the pioneering work of Andersen in 1962 to more recent methods. Sulfoxides have become associated with many diverse areas of synthetic chemistry indeed, their ability to act as a handle for the stereoselective generation of chirality at proximate centres has attracted much research worldwide. 

APPLICATIONS OF CHIRAL SULFOXIDES AS STEREOCONTROL ELEMENTS IN ORGANIC SYNTHESIS... 

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