Oxidation of organic sulphides with optically active peroxy acids. Asymmetric synthesis of sulphoxides

(+)-(3-Oxocamphorsulphonyl)oxaziridune as a highly stereoselective reagent for the oxidation of sulphides to chiral sulphoxides

“…A comparison of the selectivity of oxaziridines (1) (Table 1, entry 1) and (4) (entry 2) shows not only the much higher ability of compound (4) to induce chirality at sulphur, but also the fact that the configuration of the sulphoxide formed is reversed. We explain this by the different stereochemical environment of the oxaziridine moiety [sp3-carbon in (l), and sp2-carbon in (2)] which leads to different approaches of the smaller and larger substituents of the sulphide to the oxygen atom of the oxaziridine ring, as shown in the Figure . Entries [2][3][4][5][6][7][8][9][10][11][12][13] show the solvent dependence of the oxidations of thioanisole at room temperature, indicating the general tendency to higher e.e.s in solvents of lower polarity, despite the limited solubility of compound (4) in these solvents. However, hexane gives only poor results, while tetrachloromethane seems to be the solvent of choice.…”

Absolute Configuration and Optical Rotatory Power of Sulfoxides and Sulfinate Esters1,2

“…Rotations of such compounds in the optically pure state are generally high (see text, e.g., Table I). The [a]o values of the sulfoxides obtained in the asymmetric oxidations using peracids75 [77][78][79][80] were uniformly low and generally ranged from 1 to 5°. Taking 5 % as a conservative upper limit for the optical purity of the sulfoxides produced in these asymmetric oxidations, * of the diastereomeric transition states is ca.…”

Enantioselective Synthesis of Sulfoxides: 2000−2009

“…Low enantioselectivity (2−26% ee ) and moderate yields (47−60%) were observed when chiral dioxirane 152 generated in situ from pyranose-derived ketone was used for the oxidation of alkyl aryl sulfides . These examples, and the previous attempts with chiral peracids (up to 20% ee ) − and N -chlorocaprolactam ( ee below 3%) clearly show that although, in principle, each organic oxidant can be converted into a nonracemic derivative, the asymmetric induction can be disappointingly inefficient. As a result, chiral oxaziridines remain unrivaled in the field of metal-free enantioselective sulfoxidation.…”