3-Trifluoromethylindoline-2-one derivatives were prepared in a visible-light photocatalytic transformation of acrylamides. The arylation-cyclization sequence was initiated
Herein, we report a novel approach to the acceleration of palladium catalyzed C-H activation reactions. We demonstrated that the utilization of electron deficient triaryl boranes as Lewis acidic co-catalyst of palladium enables the directed cross dehydrogenative coupling of aldehydes and anilides under mild reaction conditions. Study of the kinetic profile of the transformation reveals a unique, unexpectedly long induction period of the transformation.
We report a new method for determination of rate constants of processes in solution using electrospray ionization mass spectrometry (ESI-MS). The investigated reaction is C-H activation of acetanilides by palladium(II)trifluoroacetate leading to stable organopalladium complexes. The rate constants can be determined from an experiment with a couple of differently substituted acetanilides being in competition activated by the palladium salt. The formed organopalladium complexes can be detected by ESI-MS. The time dependence is achieved by adding one of the acetanilides to the reaction mixture with a time delay. The kinetics can be then evaluated from the evolution of the ratio of the ESI-MS signals of differently substituted complexes as a function of the time delay. The Hammett analysis of the rate constants obtained for a series of meta-and para-substituted acetanilides provides the ρ value of-1.5, which is in agreement with values reported for similar C-H activations. We have investigated the very same reaction also with UV-Vis spectroscopy that gave us about three times smaller rate constants, but the same trend with the ρ value of-1.6. The rate constants determined by ESI-MS are directly linked to the occurrence of organopalladium complexes, whereas the UV-Vis data are associated with an absorption spectra change that could involve more reaction steps. DFT calculations support the interpretation of the reaction mechanism as cyclopalladation and provide the ρ value in the same range. The rate determining step corresponds to the agostic C-H transition structure.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.