Mechanism of C−H Bond Activation/C−C Bond Formation Reaction between Diazo Compound and Alkane Catalyzed by Dirhodium Tetracarboxylate

Abstract

The B3LYP density functional studies on the dirhodium tetracarboxylate-catalyzed C-H bond activation/C-C bond formation reaction of a diazo compound with an alkane revealed the energetics and the geometry of important intermediates and transition states in the catalytic cycle. The reaction is initiated by complexation between the rhodium catalyst and the diazo compound. Driven by the back-donation from the Rh 4d(xz) orbital to the C[bond]N sigma*-orbital, nitrogen extrusion takes place to afford a rhodium[bond]carbene complex. The carbene carbon of the complex is strongly electrophilic because of its vacant 2p orbital. The C[bond]H activation/C[bond]C formation proceeds in a single step through a three-centered hydride transfer-like transition state with a small activation energy. Only one of the two rhodium atoms works as a carbene binding site throughout the reaction, and the other rhodium atom assists the C[bond]H insertion reaction. The second Rh atom acts as a mobile ligand for the first one to enhance the electrophilicity of the carbene moiety and to facilitate the cleavage of the rhodium[bond]carbon bond. The calculations reproduce experimental data including the activation enthalpy of the nitrogen extrusion, the kinetic isotope effect of the C[bond]H insertion, and the reactivity order of the C[bond]H bond.

Late-stage C–H functionalization of complex alkaloids and drug molecules via intermolecular rhodium-carbenoid insertion

“…Since C-H insertion product 3 was not observed, it suggests that ylide formation and carbenoid C-H insertion proceed through different reaction pathways. Indeed, we speculate that product 3 is formed via direct C-H insertion induced by the metal carbene 39,40 . This being the case, it is remarkable that 3 is the sole C-H insertion product observed from a molecule that has numerous potential sites for C-H functionalization.…”

Research Progress ofα-Diazophosphonates

“…卡宾, 之后卡宾碳与氮原子或氧原子作用形成叶立德 [12] , 随后发生 1,2-氢迁移, 金属催化剂离去, 从而形成相应 的插入产物(Scheme 6), 这一点与金属卡宾 C-H 键插 入的三中心两电子机理有很大不同 [13] . …”

DFT investigation on mechanism of dirhodium tetracarboxylate-catalyzed O-H insertion of diazo compounds with H2O

“…The mechanisms of Rh(II) carbene inserting into C-H and Si-H bond have been studied by many experiments [3][4][5][6][7][8][9]. Theoretical research on the Rh(II) carbene insertion into C-H bond has been performed in detail [10][11][12]. Both experimental and theoretical studies support the concerted insertion mechanism.…”