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

Org Lett. 2018 Mar 16;20(6):1521-1525. doi: 10.1021/acs.orglett.8b00219. Epub 2018 Mar 2.

Abstract

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 iPr2NEt 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.

Publication types

  • Research Support, Non-U.S. Gov't