Oxidation of racemic sulfides

The Kagan reagent allowed Ando et al. to prepare several nonracemic sulfoxides (62) by oxidation of (61) [154]. One calculates from ee s and product distribution, using the formula for kinetic resolution [148-150], that the selectivity factor s is close to 12. A P-lactam (63) has been also resolved (s = 7) using the Kagan reagent [155]. 

The Modena reagent is the basis of a new method for the resolution of chiral ketones [59]. Thus, ( )-menthone was transformed into 1,3-dithiolane (65) and oxidized using TBHP. The two 5-monooxides were separated, and the major one gave after cleavage (-)-menthone (93% ee). The Modena procedure is also very successful in the preparation of nonracemic 1,1 -binaphthyl-2,2 -dithiol (66a) [156,157]. Monooxidation of the dimethyl dithioether (66b) furnished an almost 1 1 mixture of diastereoisomeric sulfoxides (each with 98% ee). When the two sulfur atoms of (66) are connected by a carbon chain, such as in (66c) or (66d), the 

The resolution of a racemic iron acetyl complex was achieved by Davies and Becker by its transformation into a 1 1 mixture of diastereoisomeric sulfides (67a) and (67b) [158]. Oxidation by mCPBA operates selectively on one diastereoisomer (because of a suitably located hydroxy group). The sulfoxide (68) was easily separated from sulfide (67b) and desulfurized to give the desired target. This a case of kinetic resolution of an equimolar mixture of diastereoisomers. 

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