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

Suginome, Michinori; Yamamoto, Takeshi; Nagata, Yuuya; Yamada, Tetsuya; Akai, Yuto

doi:10.1351/PAC-CON-11-08-23

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

http://dx.doi.org/10.1351/PAC-CON-11-08-23

Published online 2012-02-03

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

Michinori Suginome^1,2*, 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.