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There has been an increasing interest in simple and functionalized -amino acids and their derivatives. 1,2 A potentially straightforward methodology for their synthesis is the conjugate addition of nitrogen nucleophiles to R, -unsaturated derivatives. Diastereoselective additions in which the nitrogen nucleophile or the R, -unsaturated substrate is chiral have been reported in the literature. 3 However, only one report 4 of chiral Lewis acidcatalyzed additions of amines has appeared (maximum ee of 42%). 5 We disclose here high levels of enantioselectivity in the conjugate addition of O-benzylhydroxylamine to R, -unsaturated pyrazole amides using catalytic amounts of a chiral Lewis acid prepared from MgBr 2 ‚OEt 2 and a bisoxazoline. We also show that the opposite enantiomer of the product can be selected by a simple change of the Lewis acid. Furthermore, in at least one example the kinetic enantioselectivity can be enhanced by preferential destruction of the minor enantiomer.We have recently described enantioselective free radicalmediated conjugate additions to R, -unsaturated derivatives with chiral Lewis acids. 6 We were intrigued by the potential of these chiral Lewis acid/unsaturated amide combinations toward the addition of amines. Our experiments began with the addition of O-benzylhydroxylamine (1.

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In this paper, we demonstrate the first examples of chiral Lewis acid catalysis in the formation of tetrahydro-1,2-oxazines with very high enantioselectivity starting with diactivated cyclopropanes and nitrones (>90% yields and ee). Reactions with racemic substituted cyclopropanes provide approximately 1:1 diastereomeric tetrahydro-1,2-oxazine products with high enantioselectivity. Mechanistic information for the formation of the tetrahydro-1,2-oxazines is also detailed.