Diastereoselective epoxidation of oxazolidine-substituted alkenes by dimethyldioxirane and m-chloroperbenzoic acid: pi-facial control through hydrogen bonding by the urea functionality.
[figure: see text] A high diastereoselectivity (up to > 98:2) is found for the DMD and m-CPBA epoxidations of chiral oxazolidine-substituted olefins with a urea group. The selectivity is explained in terms of hydrogen bonding between the remote NH group of the urea functionality and the epoxidizing reagent. Methylation of the NH group prohibits hydrogen bonding, and a reversed selectivity is observed due to steric repulsion between the reagent and the urea functionality.
Adam
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Institut für Organische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany. adam@chemie.uni-wuerzburg.de
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D000475:Alkenes / Q000737:chemistry*; D000588:Amines / Q000737:chemistry; D002384:Catalysis; D002723:Chlorobenzoates / Q000737:chemistry*; D004852:Epoxy Compounds; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008745:Methylation; D015394:Molecular Structure; D010080:Oxazoles; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D014508:Urea / Q000737:chemistry*
D000475:Alkenes; D000588:Amines; D002723:Chlorobenzoates; D004852:Epoxy Compounds; D010080:Oxazoles; C064210:oxazolidine; D014508:Urea; C000433:3-chloroperbenzoic acid; C064455:dimethyldioxirane