Chemo- and Enantioselective Pd/B Hybrid Catalysis for the Construction of Acyclic Quaternary Carbons: Migratory Allylation of O-Allyl Esters to α-C-Allyl Carboxylic Acids

Abstract

We describe herein the asymmetric synthesis of α-allyl carboxylic acids containing an α-quaternary stereocenter by a chiral hybrid catalyst system comprising palladium and boron complexes. The reaction proceeded through palladium-catalyzed ionization of α,α-disubstituted O-allyl esters for the generation of chiral π-allyl palladium complex as an electrophile, boron-catalyzed enolization of the carboxylate part for the generation of chiral α,α-disubstituted carboxylic acid-derived enolates as a nucleophile, and enantioselective coupling between the thus-generated nucleophile and electrophile. Proper combinations of chiral ligands for the boron and palladium catalysts were crucial. The reaction proceeded chemoselectively at the α-position of the carboxylic acid group.

Catalytic Enantioselective Synthesis of Acyclic Quaternary Centers: Palladium-Catalyzed Decarboxylative Allylic Alkylation of Fully Substituted Acyclic Enol Carbonates

“…10 Recently, Shimizu and Kanai demonstrated the preparation of acyclic α-quaternary carboxylic acids via allylic alkylation utilizing a hybrid boron-palladium catalytic system (Figure 1D). 11…”

Data-Driven Catalyst Optimization for Stereodivergent Asymmetric Synthesis of α-Allyl Carboxylic Acids by Iridium/boron Hybrid Catalysis

“…Following this pioneering work, stereodivergent Ir-catalyzed allylic substitutions with prochiral enolates derived from ketones [21][22][23] , esters [24][25][26][27][28][29] and amides 30 were reported. As a target reaction of our data-driven catalyst optimization, we chose the catalytic asymmetric migratory -C-allylation of allyl esters 1 to afford -allyl carboxylic acids 2, using a combination of a chiral Ir complex catalyst [31][32][33] and a chiral boron (B) complex catalyst 34 (Fig. 1b).…”

Data-driven catalyst optimization for stereodivergent asymmetric synthesis of α-allyl carboxylic acids by iridium/boron hybrid catalysis

“…Following this pioneering work, stereodivergent Ir-catalyzed allylic substitutions with prochiral enolates derived from ketones [21][22][23] , esters [24][25][26][27][28][29] and amides 30 were reported. As a target reaction of our data-driven catalyst optimization, we chose the catalytic asymmetric migratory -C-allylation of allyl esters 1 to afford -allyl carboxylic acids 2, using a combination of a chiral Ir complex catalyst [31][32][33] and a chiral boron (B) complex catalyst 34 (Fig. 1b).…”