Density Functional Theory Mechanistic Study of Ni-Catalyzed Reductive Alkyne–Alkyne Cyclodimerization: Oxidative Cyclization versus Outer-Sphere Proton Transfer

Abstract

Density functional theory mechanistic study of the nickelcatalyzed reductive alkyne−alkyne cyclodimerization with CH 3 OH/BEt 3 unveils that, after forming a nickel-alkyne π complex, the reaction prefers outer-sphere proton transfer rather than the common alkyne−alkyne oxidative cyclization. The outperformance of aminophosphine ligand (L1) is attributed to its bidentate coordination that favors the proton transfer, the labile −NH 2 and strong electron-donating −PPh 2 arms and adequate Ni−P distance that allow the hydrogen transfer of the ethyl group of MeO-BEt 3 − .

Mechanistic Studies of Nickel-Catalyzed Hydroarylation of Styrenes

“…On the basis of experiments , and previous reports, , two different pathways can be proposed for the hydroarylation process (Scheme ). Path A includes the alcohol O–H oxidative addition to Ni(0) center leading to the Ni­(II)–H species, which undergoes olefin insertion to form an alkylnickel­(II) species that experiences transmetalation and reductive elimination to generate the hydroarylation product.…”

Ni-Catalyzed Reductive Coupling of Alkynes and Amides to Access Multi-Functionalized Indoles

“…σ-Bond metathesis of nickellacycle intermediates was achieved using silanes and trialkyl borane reagents, and the transmetalation (TM) of nickellacycles with R–M complexes is another efficient approach for accessing more diverse functionalities (Scheme a) . In addition, this reductive coupling via a nickellacycle was also extensively explored in a diverse range of cycloaddition reactions . Earlier, the reductive coupling of aldehydes and alkynes as π-components was predominantly explored, and later the approach was expanded to other π-components such as nucleophilic allenes/alkenes and electrophilic ketones/imines.…”

On-Surface Synthesis of 2D Porphyrin-Based Covalent Organic Frameworks Using Terminal Alkynes

“…To determine the origin of the observed selectivity, that is, the preference of alkyne–alkyne cyclodimerization on Au(111), we investigated the reaction pathway of the alkyne–alkyne cyclodimerization on Au(111) by DFT simulations. Mechanistically, transition metal-catalyzed cyclization reactions commence with oxidative cyclization to generate a metallacycle species as the key intermediate. − To save computational resources, we used phenylacetylenes instead of TEPP molecules to simulate the Au-catalyzed alkyne–alkyne cyclodimerization, while climbing image nudged elastic band calculation (CI-NEB) was used to obtain the energy curve. As shown in Figure , the terminal alkynes first abstracted a gold atom from the Au(111) surface to generate an organometallic five-membered ring via oxidative cyclodimerization.…”