Can Li, Weiping Zhang, Xiumei Liu
Mar 1, 2001
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Journal
Chinese Journal of Catalysis
Abstract
The role of trifluoromethanesulfonate ion (OTf-) in asymmetric cyclopropanation of styrene catalyzed by ruthenium complex of chiral N, P ligand is investigated by in situ variable temperature F-19 NMR. The temperature of NMR experiment varies from 243 K to 283 K. After ethyl diazoacetate and styrene are added into the catalytic system, the process that the OTf- leaves from the central metal is observed from the change of the F-19 NMR spectra. Owing to the weakly coordinating behavior, trifluoromethanesulfonate ion can be easily removed from the central metal and replaced by substrates to form the reactive intermediate during the reaction. So that the catalytic reactivity can be improved greatly when the silver trifluoromethanesulfonate is added to the catalytic system.