Mechanistic Studies of the TRIP-Catalyzed Allylation with Organozinc Reagents

Abstract

3,3-Bis(2,4,6-triisopropylphenyl)-1,1-binaphthyl-2,2-diyl hydrogenphosphate (TRIP) catalyzes the asymmetric allylation of aldehydes with organozinc compounds, leading to highly valuable structural motifs, like precursors to lignan natural products. Our previously reported mechanistic proposal relies on two reaction intermediates and requires further investigation to really understand the mode of action and the origins of stereoselectivity. Detailed ab initio calculations, supported by experimental data, render a substantially different mode of action to the allyl boronate congener. Instead of a Brønsted acid-based catalytic activation, the chiral phosphate acts as a counterion for the Lewis acidic zinc ion, which provides the activation of the aldehyde.

Nickel‐Mediated Enantioselective Photoredox Allylation of Aldehydes with Visible Light

“…On the one hand, several effective enantioselective methodologies, with different nucleophilic allylating reagents (i.e. allylic stannanes, [17] allylic halides, [18] allylic acetates, [19] and allylic boronates [20] ), have been reported. However, such useful and important protocols shown some drawbacks and limitations.…”

Asymmetric Allylation Catalyzed by Chiral Phosphoric Acids: Stereoselective Synthesis of Tertiary Alcohols and a Reagent‐Based Switch in Stereopreference

“…A rationale of this remarkable switch in stereoselectivity may be found in the higher flexibility of the open‐chained reagent. Therefore the dipole moments of the reagent [22] become less dominating and steric factors, reflected in the size of the ester group become stereo‐determining. Nevertheless, these assumptions just demonstrate the working basis of more detailed calculations currently performed in our laboratories.…”