The synthesis of chiral molecules bearing adjacent stereocenters is an important objective within organic synthesis. Having complete control over the atomic arrangement in terms of both diastereo- and enantioselectivity is a difficult task. Utilization of a substituted allyl-fragment as a reaction partner presents further regioselectivity issues (α- vs. γ-carbon bond formation). In principle, the ability to combine two achiral unsaturated compounds, such that two (or more) chiral centres are formed stereodivergently in one step via asymmetric catalysis is a highly desirable process.<br/>The allylboration reaction has garnered significant interest for its ability to overcome these hurdles for the synthesis of densely functionalized homoallylic alcohols and amines. The stability of allylboronates to the dreaded 1,3-borotropic shift coupled with their high facial selectivity within the tightly closed Zimmerman-Traxler transition state allows for their successful implementation in asymmetric synthesis. Our group recently disclosed the first catalytic asymmetric allylboration of ketones with 3,3’-disubstituted allylboronic acids for the synthesis of homoallylic alcohols bearing adjacent quaternary stereocenters in high yields and enantioselectivity. Herein is the extension of this work towards cyclic imines (indoles and dihydroisoquinolines) for the synthesis of complex and biologically relevant nitrogenous architectures in an asymmetric fashion.

Catalytic asymmetric allylboration of cyclic imines for the stereodivergent synthesis of prenylated indolines and tetrahydroisoquinolines

253rd National Meeting (2017)

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