Reaction of Optically Active α-Aminoallenylstannanes with Aldehydes Formed in Situ from the Lewis-Acid-Catalyzed Rearrangement of Epoxides

Reaction of optically active α-oxazolidinonylallenylstannanes with oxiranes in the presence of BF₃·OEt₂ produced β-hydroxypropargylamines with high syn diastereoselectivity and high enantioselectivity through an initial Lewis-acid-catalyzed rearrangement of the oxirane to the corresponding aldehyde via an alkyl, aryl, or hydride shift. This permits the use of readily available oxiranes as alternatives to aldehydes that are difficult to prepare and/or unstable.