A Regulation of Regiodivergent Routes for Enantioselective Aldol Addition of 2-Alkyl Allenoates with Aldehydes: α-Addition versus γ-Addition

다국어 초록 (Multilingual Abstract)

<P>A method for the regioselective asymmetric aldol addition of 2-alkyl allenoates with aldehydes to provide an α- or γ-adduct depending on the aldehyde pair is reported. In most cases, except enals, a mixture of a chiral bromoborane with 2-alkyl allenoates in the presence of <I>i</I>Pr<SUB>2</SUB>NEt can react with aldehydes to provide efficient γ-addition products as single isomers containing axial and central chirality. On the other hand, observations indicate that enals undergo α-addition to yield highly functionalized adducts, including an α-carbon quaternary center in high levels of diastereo- and enantioselectivity.</P>
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