Chiral sulfoxide

Verify, by making molecular models, that the bonds to sulfur are arranged in a trigonal pyramidal geometry in sulfoxides and in a tetrahedral geometry in sulfones. Is phenyl vinyl sulfoxide chiral What about phenyl vinyl sulfone ... 

Besides simple alkyl-substituted sulfoxides, (a-chloroalkyl)sulfoxides have been used as reagents for diastereoselective addition reactions. Thus, a synthesis of enantiomerically pure 2-hydroxy carboxylates is based on the addition of (-)-l-[(l-chlorobutyl)sulfinyl]-4-methyl-benzene (10) to aldehydes433. The sulfoxide, optically pure with respect to the sulfoxide chirality but a mixture of diastereomers with respect to the a-sulfinyl carbon, can be readily deprotonated at — 55 °C. Subsequent addition to aldehydes afforded a mixture of the diastereomers 11A and 11B. Although the diastereoselectivity of the addition reaction is very low, the diastereomers are easily separated by flash chromatography. Thermal elimination of the sulfinyl group in refluxing xylene cleanly afforded the vinyl chlorides 12 A/12B in high chemical yield as a mixture of E- and Z-isomers. After ozonolysis in ethanol, followed by reductive workup, enantiomerically pure ethyl a-hydroxycarboxylates were obtained. 

In the alkylation of optically active 2-(phenylsulfinyl)ethanol, the only stereogenic center is the sulfoxide, hence, the result shows the net asymmetric induction of the sulfoxide chirality 87. Good stereoselectivity was obtained. 

Some chiral versions of 1.3-dipolar cycloadditions with nitrones, utilizing chiral sulfoxides, chiral nitrones, and sulfones substituted with a chiral group, are known. 

The presence of the menthyl group in the ester moiety allows the easy resolution of chiral sulfoxides by fractional crystallization, but does not influence the stereochemical outcome of the reaction. Diastereoselectivity is primarily due to the sulfoxide chirality and cycloaddition of the corresponding sulfones shows low or even lack of diastereoselectivity33. The results of the noncatalyzed [4 + 2] cycloaddition of cyclopentadiene (2), or furan (10) to (Z)- and ( )-3-sulfmyl-2-propenoic acids 9 and esters 15 are shown in Tables 2 and 3. 

A closely related stereochemical feature of the allylic sulfoxide-to-sulfenate rearrangement involves sulfur-to-carbon (S C) chirality transfer. Trapping of the sulfenate with a thiophile has the potential to relay stereochemical information from the sulfoxide chiral center to the carbinol center of the allylic alcohol product. This stereochemical transfer originates from a preference for either the exo or the endo transition state, with the latter typically predominating. Thus, as shown in Scheme 18.8. for a fixed configuration at the sulfoxide S-center and the E-alkene geometry, the exo and endo transition states provide enantiomeric... 

Enantiopure sulfinimines are ammonia imine synthons useful in the asymmetric synthesis of amines and -amino acid derivatives. Sulfinimines unavailable via the Andersen synthesis (R = H) are prepared hy asymmetric oxidation of the sulfenimines, ArS-N=C(R)PhX, with (+)-( ) or (-)-(1) at -20 to 20 °C in CCI4 (eq 8). Crystallization improves the ee to >95%. The sulfoxide chiral recognition model correctly predicts the configuration of the product. 

Synthesis of Chiral Sulfoxides. Chiral sulfoxides have been used extensively in asymmetric synthesis. An extremely... 

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