Sulfoximines hydroxysulfoximines

A series of chiral p-hydroxysulfoximine ligands have been synthesised by Bolm et al. and further investigated for the enantioselective conjugate addition of ZnEt2 to various chalcone derivatives. The most eiScient sulfoximine, depicted in Scheme 2.33, has allowed an enantioselectivity of up to 72% ee to be obtained. These authors assumed a nonmonomeric nature of the active species in solution, as suggested by the asymmetric amplification in the catalysis with a sulfoximine of a low optical purity. 

Ketones. The lithio derivative of ( +)-(.S )-. Y,.S -dimethyl-S-phenylsulfoxiinine (16), or its enantiomer, may be used both to resolve racemic ketones164 and to determine absolute configurations of ketones. For example, rac-19 on addition of 16 formed the diastereomeric /j-hydroxy-sulfoximines 17 and 18 which were separated. The configuration of 17 was established by an X-ray analysis. The ketones can be regenerated from the /1-hydroxysulfoximines by thermolysis. Thus, heating of 17 and 18 to 80 °C (for 12 h) furnished 19 [a precursor of (+ )-modhephen] and ent-l9165. 

Simmons-Smith cyclopropanation of -hydroxysulfoximines (equation 74) . However, access to the pure bicyclo[3.1.0] derivative required chromatographic separation of the diastereomeric sulfoximine adducts. 

Application of a polymer-supported enantiopure sulfoximine in stereoselective conversion into hydroxysulfones has been reported (Scheme 12.30) [13, 41]. The chiral sulfoximine resin was prepared by coupling the sulfoximine potassium salt 78, in the presence of tetrabutylammonium bromide (TBAB), to Merrifield resin. Hydroxyalkylation of the polymer-bound sulfoximine 79 at the a-position with benzaldehyde and propanal furnished the hydroxysulfoximine resin 80. Oxidative cleavage gave hydroxysulfones 81 in 81 and 84% yield and enantiomeric excesses of 24 and 26% ee. 

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