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Chiral kinetic resolution of sulfoxides and selenoxides/carbanion hydroxylation using 2-sulfonyloxaziridines
Dissertation

Chiral kinetic resolution of sulfoxides and selenoxides/carbanion hydroxylation using 2-sulfonyloxaziridines

Joanne M. Billmers
Doctor of Philosophy (Ph.D.), Drexel University
1984
DOI:
https://doi.org/10.17918/00008557
pdf
Billmers_Joanne_19847.28 MB
PDF Access upon request, Email title, URL, or DOI to archives@drexel.edu

Abstract

Chemical tests and reagents Sulfur compounds
2-Benzenesulfonyl-3-aryloxaziridines provide a novel class of aprotic oxidizing reagent useful for the conversion of sulfoxides to sulfones, selenides to selenoxides and carbanions to alcohols. The mechanism of oxaziridine oxygen transfer was investigated and involves nucleophilic attack on the electron deficient oxaziridine oxygen atom and subsequent oxygen transfer. The oxidative kinetic resolution of sulfoxides (R-S(O)-R') using chiral 2-sulfonyloxaziridines was found to produce optically active sulfoxides in 0.2-27% enantiomeric excess (e.e.). The configuration of the oxaziridine three-membered ring determines the configuration of sulfoxide obtained and the structure of the oxaziridine substituents affects the extent of asymmetric induction. An investigation of selenoxide (R-Se(O)-R') configurational lability was undertaken and resulted in the firs example of a simple optically active selenoxide, 2,4,6 triisopropylphenyl methyl selenoxide. This was prepared via a kinetic resolution process employing d-and 1-10 camphorsulfonamide. The racemization of optically active selenoxides through achiral hydrate formation resulting from addition of water across the Se-O bond has been proven to occur in simple chiral selenoxides and was found to be acid catalyzed. The carbanion hydroxylation properties of 2-benzenesulfonyl-3-aryloxaziridines were also investigated, producing alcohols and phenols from both aliphatic and aromatic Grignard and lithium reagents in good yield. The sulfonimine by-product of oxidation reacts competitively with nucleophiles to form carbon-substituted benzenesulfonamides. Resonance-stabilized enolate carbanions were also oxidized, producing (alpha)-hydroxylated carbonyl compounds. Esters and ketones were hydroxylated in good yield by treatment with potassium tert-butoxide in ether or THF and addition of the oxaziridine in hexamethyl phosphoramide (HMPA). 2-Benzenesulfonyl-3-aryloxaziridines have also successfully hydroxylated ketosteroids and silylenol ethers in good yield.

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