Determination of the absolute configuration of optically active 2,2-dimethyl-3,4-epoxychromans prepared by the catalytic enantioselective epoxidation with the dimethyldioxirane/Jacobsen Mn(III)salen system
✍ Scribed by Waldemar Adam; József Jekö; Albert Lévai; Zsuzsa Majer; Csaba Nemes; Tamás Patonay; László Párkányi; Péter Sebök
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 531 KB
- Volume
- 7
- Category
- Article
- ISSN
- 0957-4166
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✦ Synopsis
Enantioselective epoxidation of 2,2-dimethyl-2/-/-chromenes la-d by using Mn(III)salen complexes (R,R)-3 and (S,S)-3 as catalysts and dimethyldioxirane (DMD) as oxygen donor afforded optically active 2,2-dimethyi-3,4-epoxychromans 2a-d in good yields and high enantioselectivities (up to 93% e.e.). The absolute configuration of the ( 3S, 4S)-6, 7-bis(tosyloxy)-2,2-dimethyl-3,4-epoxychroman (3S,4S)-2d has been determined by X-ray diffraction. The absolute configurations of the other nonraeemic epoxychromans were assigned by circular dichroism (CD) measurements relative to the (3S,4S)-2d epoxide as reference compound.