Catalytic Cycle for N–CN Bond Cleavage by Molybdenum Silyl Catalyst: A DFT Study

Imine hydrosilylation using an iron complex catalyst: A computational study

The reaction mechanism for imine hydrosilylation in the presence of an iron methyl complex and hydrosilane was studied using density functional theory at the M06/6-311G(d,p) level of theory. Benzylidenemethylamine (PhCH = NMe) and trimethylhydrosilane (HSiMe₃ ) were employed as the model imine and hydrosilane, respectively. Hydrosilylation has been experimentally proposed to occur in two stages. In the first stage, the active catalyst (CpFe(CO)SiMe₃ , 1) is formed from the reaction of pre-catalyst, CpFe(CO)₂ Me, and hydrosilane through CO migratory insertion into the FeMe bond and the reaction of the resulting acetyl complex intermediate with hydrosilane. In the second stage, 1 catalyzes the reaction of imine with hydrosilane. Calculations for the first stage showed that the most favorable pathway for CO insertion involved a spin state change, that is, two-state reactivity mechanism through a triplet state intermediate, and the acetyl complex reaction with HSiMe₃ follows a σ-bond metathesis pathway. The calculations also showed that, in the catalytic cycle, the imine coordinates to 1 to form an FeCN three-membered ring intermediate accompanied by silyl group migration. This intermediate then reacts with HSiMe₃ to yield the hydrosilylated product through a σ-bond metathesis and regenerate 1. The rate-determining step in the catalytic cycle was the coordination of HSiMe₃ to the three-membered ring intermediate, with an activation energy of 23.1 kcal/mol. Imine hydrosilylation in the absence of an iron complex through a [2 + 2] cycloaddition mechanism requires much higher activation energies. © 2018 Wiley Periodicals, Inc.

Intramolecular aminocyanation of alkenes by cooperative palladium/boron catalysis

A cooperative palladium/triorganoboron catalyst to accomplish the intramolecular aminocyanation of alkenes through the cleavage of N-CN bonds is reported. 4,5-Bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) is found to be crucial as a ligand for palladium to effectively catalyze the transformation with high chemo- and regioselectivity. A range of substituted indolines and pyrrolidines with both tetra- or trisubstituted carbon and cyano functionalities are readily furnished by the newly developed cyanofunctionalization reaction. A preliminary example of enantioselective aminocyanation is also described.

Transformations of X (C, O, N)-CN Bonds: Cases of Selective X (C, O, N)-C Activation

Activation of C-C, C-N, and C-O bonds has in recent decades been recognized as a valuable strategic objective. While considerable progress has been achieved, many of the more challenging issues, e.g., regioselective activation of specific C-X (C, O, N) bonds, chemoselective cleavage of C_(sp3)-X bonds, enantioselective activation and even the successful application of solid catalysts in such transformations remain elusive. The research disclosed herein summarize recent advances in C-X bond cleavages, including regioselective processes, although the carbon is activated in the form of a cyano group.