摘要：

Enantioslelective routes to optically active 1,2-diols are of considerable interest since this structural moiety is widely found in biologically active natural products and synthetic pharmaceuticals. A number of methods for their synthesis have been developed and, among them, the Sharpless asymmetric dihydroxylation of olefins is most often used. Another potential route to chiral 1,2-diols is the asymmetric α-hydroxylation of aldehydes and subsequent reduction. However, a direct chemical methods for the α-hydroxylation of aldehydes has not been reported. This is because of the facile aldol reactions that occur during enolate formation. The only example leading to α-hydroxyaldehydes in high enantiomeric purity is shown by the oxidation of preformed enolates from aldehydes derivatized with chiral auxiliaries. For these reasons, the development of new methodologies for the direct catalytic enantioselective α-hydroxylation of aldehydes has become an intriguing target in organic synthesis. Recent studies in enamine chemistry in which chiral amines were employed to mimic enzymatic catalysis have led to the utilization of aldehydes as donors to form C-C bonds (for example, in aldol, Mannich, Michael, and Diels-Alder reactions) and C-N bonds (in Michael-like amination). In contrast to the classic preformed enolates, these reactions are believed to proceed through the direct in situ production of enamines from aldehydes, in a similar way to natural enzymes. These findings prompted us to investigate whether the amine catalysts could be applied to the formation of a C-O bond in the asymmetric α-aminoxylation of aldehydes.

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