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Pure Appl. Chem., 2012, Vol. 84, No. 8, pp. 1759-1769

Published online 2012-02-03

Catalytic asymmetric synthesis using chirality‑switchable helical polymer as a chiral ligand

Michinori Suginome1,2*, Takeshi Yamamoto2, Yuuya Nagata2, Tetsuya Yamada2 and Yuto Akai2

1 CREST, JST, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
2 Department of Synthetic Chemistry and Biological Chemistry, Kyoto University, Kyoto, Japan

Abstract: Single-handed PQXphos, i.e., helical poly(quinoxaline-2,3-diyl)s bearing diarylphosphino pendant groups, served as remarkable chiral ligands in palladium-catalyzed asymmetric hydrosilylation of styrenes and asymmetric biaryl synthesis by Suzuki–Miyaura coupling, affording up to 98 % enantiomeric excess (e.e.) in both reactions. A palladium complex of high-molecular-weight variant (1000mer) of PQXphos could be reused eight times by virtue of the formation of an insoluble polymer complex. PQXphos underwent solvent-dependent inversion of the helical sense, enabling production of either of two enantiomeric products using a single PQXphos.