Study on the role of trifluoromethanesulfonate ion in asymmetric cyclopropanation of styrene by in situ. Variable temperature F-19 NMR

The role of trifluoromethanesulfonate ion (OTf-) in asymmetric cyclopropana tion of styrene catalyzed by ruthenium complex of chiral N, P ligand is inv estigated 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. Owi ng to the weakly coordinating behavior, trifluoromethanesulfonate ion can b e easily removed from the central metal and replaced by substrates to form the reactive intermediate during the reaction. So that the catalytic reacti vity can be improved greatly when the silver trifluoromethanesulfonate is a dded to the catalytic system.