Highly efficient asymmetric synthesis of vinylic amino alcohols by Zn-promoted benzoyloxyallylation of chiral N-tert-butanesulfinyl imines: facile and rapid access to (-)-cytoxazone.

An efficient and convenient alpha-hydroxyallylation approach for the asymmetric synthesis of a variety of beta-amino-alpha-vinyl alcohols has been successfully developed. A wide range of vinylic amino alcohol derivatives could be obtained in very good yields and with excellent diastereomeric ratios of up to 99:1 in favor of anti isomers by highly diastereoselective Zn-promoted benzoyloxyallylation of chiral N-tert-butanesulfinyl imines with 3-bromopropenyl benzoate at room temperature. In particular, excellent enantioinduction of the two new stereogenic centers was observed, with up to 98% ee. The method provides a new route for the direct alpha-hydroxyallylation of imines in a highly stereoselective manner. Moreover, the synthetic value of the method has also been demonstrated by the most concise and straightforward synthesis of (-)-cytoxazone yet reported.