Activity, absolute, 178 - sulphides

In 1960, Montanari and Balenovic and their coworkers described independently the first asymmetric oxidation of sulfides with optically active peracids. However, the sulphoxides were formed in this asymmetric reaction (equation 130) with low optical purities, generally not higher than 10%. The extensive studies of Montanari and his group on peracid oxidation indicated that the chirality of the predominantly formed sulphoxide enantiomer depends on the absolute configuration of the peracid used. According to Montanari the stereoselectivity of the sulphide oxidation is determined by the balance between one transition state (a) and a more hindered transition state (b) in which the groups and at sulphur face the moderately and least hindered regions of the peracid,... 

Optically active phenyl-t-butylphosphine oxide with the same sign of rotation has been prepared by the reaction of Raney nickel with the (+)-selenide (107) and the (+)-sulphide (108),82 which suggests that the latter compounds have the same sign of rotation for the same absolute configuration. The absolute configuration of (—)-phenyl-t-butylphosphine oxide was apparently established by conversion into (—)-methylphenyl-t-butylphosphine oxide, but no details have been given. 

Continuing their investigation of the stereochemistry of tervalent phosphorus, Mikolajczyk and his co-worker have shown that optically active O-methyl ethyl-phenylphosphinite (112) and S -ethyl ethylphenylthiophosphinite (113) react with methyl-lithium and sodium methoxide with predominant inversion of configuration at phosphorus. The absolute configuration of (113) was established by conversion into ethylmethylphenylphosphine sulphide, and the stereochemical course of the nucleophilic displacements was determined by conversion of the initial products into the corresponding oxide and sulphides, as shown in Scheme 9. 

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