Enhanced catalyst activity and enantioselectivity with chirality-switchable polymer ligand PQXphos in Pd-catalyzed asymmetric silaborative cleavage of meso-methylenecyclopropanes.
The poly(quinoxaline-2,3-diyl)-based helically chiral phosphine ligands PQXphos exhibited high enantioselectivities up to 97% ee in palladium-catalyzed desymmetrization of meso-1,2-dialkylsubstituted-3-methylenecyclopropanes through silaborative cleavage of the C-C bond. The observed enantioselectivities were higher than those obtained with 2-diarylphosphino-1,1'-binaphthyl in our original report. Remarkable rate enhancement was also observed with a series of PQXphos in comparison with the corresponding low-molecular weight ligands.
Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
Yuto
Y
Akai
Takeshi
T
Yamamoto
Yuuya
Y
Nagata
Toshimichi
T
Ohmura
Michinori
M
Suginome