Helically Chiral Polyquinoxaline Carboxylates Bearing Achiral Ar₃P for Asymmetric Suzuki Coupling in Water

Keywords

asymmetric catalysis - chiral helix - palladium - phosphine ligand - polyquinoxaline - Suzuki coupling - binaphthyls

Significance

A helically chiral polymer-based triarylphosphine ligand (S)-PQXPhos-COOH, bearing a hydrophobic helical interior and a hydrophilic carboxylate exterior, was prepared through quinoxaline-forming co-polymerization of (S)-1-COOEt and biaryl 2. Palladium-catalyzed cross-coupling of compounds 3 and 4 took place at 40 °C in the presence of (S)-PQXPhos-COOH in water to give a 90 % yield of (S)-5 with 99 % enantioselectivity.

 

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Comment

(R)-PQXPhos-C₂H₅ , which lacks a hydrophilic exterior, exhibited lower catalytic performance in aqueous THF (42 % yield, 94 % ee) and extremely low activity in pure water (4 % yield). The (S)-PQXPhos-COOH/Pd/water system afforded a variety of axially chiral binaphthyls, naphthyl­benzenes and naphthylpyrene with excellent enantioselectivities.

 

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Publication History

Article published online:
23 June 2025