35188-22-8Relevant academic research and scientific papers
SYNTHESIS AND ABSOLUTE CONFIGURATIONS OF OPTICALLY ACTIVE OXOSULFONIUM SALTS
Takeuchi, Hiroyuki,Minato, Hiroshi,Kobayashi, Michio,Yoshida, Masato,Matsuyama, Haruo,Kamigata, Nobumasa
, p. 165 - 172 (2007/10/02)
The optically active arylethylmethyloxosulfonium perchlorates (2a-c) were prepared by the oxidation of the corresponding sulfonium salts (1a-c) with sodium perbenzoate.The absolute configurations of oxosulfonium salts were determined by converting them into aryl ethyl sulfoxides (3a-c).From the relationship of the absolute configurations of ethylmethylphenylsulfonium perchlorate (1a) and ethylmethylphenyloxosulfonium perchlorate (2a), it was found that the oxidation of sulfonium salt (+)-(S)-1a with sodium perbenzoate proceeded with retention of configuration around the sulfur atom to afford oxosulfonium salt (+)-(R)-2a.The circular dichroism (CD) spectra of optically active oxosulfonium perchlorates (2) with (+)-(R) configuration show a positive strong Cotton effect at ca. 230 nm and a positive weak one at ca. 260 nm.Whereas, the CD spectra of optically active oxosulfonium perchlorates (2) with (-)-S configuration show a negative strong Cotton effect at ca. 230 nm and a negative one at ca. 260 nm.
Asymmetric Alkylation of β-Keto Esters with Optically Active Sulfonium Salts
Umemura, Kazuyuki,Matsuyama,Haruo,Watanabe, Nobuko,Kobayashi, Michio,Kamigata, Nobumasa
, p. 2374 - 2383 (2007/10/02)
Alkylation of the cyclic β-keto ester2-(methoxycarbonyl)-1-indanone (2) with racemic alkylsulfonium salts 1a-h gave 2-alkylindanones 3 and 4 in 60-96percent yields.The relative reactivities of the alkyl substituents of aryldialkylsulfonium salts 1e and 1f were quite different from those in SN2 alkylations.Asymmetric induction occured upon alkylation of 2 with optically active sulfonium salts. (R)-2-Ethyl-2-(methoxycarbonyl)cyclohexanone (11) was obtained in up to 16percent ee by alkylation of the enolate ion of 2-(methoxycarbonyl)cyclohexanone (9) with optically active (R)-(+)-(p-chlorophenyl)ethylmethylsulfonium d-10-camphorsulfonate (1k).Alkylation of the enolate ion of 2 with sulfonium salts containing optically active alkyl groups afforded C-alkylated products with inversion of configuration at the asymmetric alkyl carbon atom.These alkylations appear to proceed via an S-O sulfurane intermediate or a tight ion pair with subsequent stereoselective alkyl migration to the enolate.
NOVEL ASYMMETRIC ALKYLATION OF CYCLIC β-KETO ESTERS WITH OPTICALLY ACTIVE SULFONIUM SALTS
Kobayashi, Michio,Umemura, Kazuyuki,Watanabe, Nobuko,Matsuyama, Haruo
, p. 1067 - 1070 (2007/10/02)
A new asymmetric alkylation of cyclic β-keto esters with optically active sulfonium salts, which are easily prepared by optical resolution methods, has been investigated.Relative reactivities for alkyl substituents are found to be quite different from tho
