Axially Chiral N‐Oxide Catalysts for the Allylation and Crotylation of Aromatic Aldehydes: Exploiting Nonlinear Effects

Abstract

AbstractA new family of IAN‐type amine N‐oxides is presented as catalysts for the allylation and crotylation of aromatic aldehydes with allyltrichlorosilanes. These reaction exhibit a remarkably positive nonlinear effect which enables utilization of the catalysts in subenantiopure form. As enantiopure catalysts are not required under this regime, the synthesis of these N‐oxides is straightforward through catalytic asymmetric synthesis, avoiding lenghty synthesis from the chiral pool or resolution of diastereoisomers. Studies of the corresponding crotylation with Z‐ and E‐crotylsilanes suggest that the reaction proceeds through a chair‐like transition state.