In this lecture,mechanistic studies of several catalytic reactions will be discussed.1(1) The study of hydrosilylation of alkynes catalyzed by Trosts Cp*Ru(NCMe)3PF6-catalyst led to the proposal of a novel reaction mechanism:oxidative-added proton addition to alkyne to form a metallocyclopropene intermediate,followed by silyl migration to give unusual Markovnikov regiochemistry and trans-addition stereochemistry.2 This mechanism can be extended to a series of reactions.3-4(2) Unexpected meta product in copper-catalyzed arylation of anilide can be explained by a Heck-like four-membered ring transition state involving a Cu(Ⅲ)-Ph species.This Cu(Ⅰ)/Cu(Ⅲ) mechanism is supported by a series of experiments.5(3) Mechanistic understanding has been developed for direct distal meta-C-H bond(more than ten bonds away) activation in tethered arene containing a remote nitrile.6-7 The mechanism can be extended to understand amino acid promoted enantioselective C-H bond activation.