Origins of Chemoselectivity in the Ni-Catalyzed Biaryl and Pd-Catalyzed Acyl Suzuki–Miyaura Cross-Coupling of N-Acetyl-Amides

A decarbonylative approach to alkylnickel intermediates and C(sp3)-C(sp3) bond formation

The myriad nickel-catalyzed cross-coupling reactions rely on the formation of an organonickel intermediate, but limitations in forming monoalkylnickel species have limited options for C(sp3) cross-coupling. The formation of monoalkylnickel(II) species from abundant carboxylic acid esters would be valuable, but carboxylic acid derivatives are primarily decarboxylated to form alkyl radicals that lack the correct reactivity. In this work, we disclose a facile oxidative addition and decarbonylation sequence that forms monoalkylnickel(II) intermediates through a nonradical process. The key ligand, bis(4-methylpyrazole)pyridine, accelerates decarbonylation, stabilizes the alkylnickel(II) intermediate, and destabilizes off-cycle nickel(0) carbonyl species. The utility of this new reactivity in C(sp3)-C(sp3) bond formation is demonstrated in a reaction that is challenging by purely radical methods-the selective cross-coupling of primary carboxylic acid esters with primary alkyl iodides.

Amide N-C Bond Activation: A Graphical Overview of Acyl and Decarbonylative Coupling

This Graphical Review provides an overview of amide bond activation achieved by selective oxidative addition of the N-C(O) acyl bond to transition metals and nucleophilic acyl addition, resulting in acyl and decarbonylative coupling together with key mechanistic details pertaining to amide bond distortion underlying this reactivity manifold.

Mechanistic views and computational studies on transition-metal-catalyzed reductive coupling reactions

Transition-metal-catalyzed reductive coupling reactions have been considered as a powerful tool to convert two electrophiles into value-added products. Numerous related reports have shown the fascinating potential. Mechanistic studies, especially theoretical studies, can provide important implications for the design of novel reductive coupling reactions. In this review, we summarize the representative advancements in theoretical studies on transition-metal-catalyzed reductive coupling reactions and systematically elaborate the mechanisms for the key steps of reductive coupling reactions. The activation modes of electrophiles and the deep insights of selectivity generation are mechanistically discussed. In addition, the mechanism of the reduction of high-oxidation-state catalysts and further construction of new chemical bonds are also described in detail.

N-Heterocyclic Carbene-Catalyzed Asymmetric C-O Bond Construction Between Benzoic Acid and o-Phthalaldehyde: Mechanism and Origin of Stereoselectivity

A computational study was contributed to explore the origin of stereoselectivity of NHC-mediated cyclization reaction between benzoic acid and o-phthalaldehyde for asymmetric construction of phthalidyl ester. The most energetically favorable pathway mainly includes the following steps: (1) nucleophilic attack on carbonyl carbon of o-phthalaldehyde by catalyst NHC, (2) formation of Breslow intermediate, (3) oxidation by DQ, (4) asymmetric formation of dual C-O bonds, and (5) dissociation of catalyst with the product. The C-O bond formation was testified as the stereoselectivity-determining step, the R-configurational pathway is more energetically favorable than the S-configurational one. The non-covalent interaction (NCI) and atom-in-molecule (AIM) analyses were performed to reveal that the O-H ⋅⋅⋅ O and C-H ⋅⋅⋅ O hydrogen-bond interactions are the key factors for controlling the stereoselectivity. The detailed mechanism and origin of stereoselectivity give useful insights for understanding organocatalytic reactions for asymmetric construction of C-O bond.

Terpyridine-based Pd(ii)/Ni(ii) organometallic framework nano-sheets supported on graphene oxide-investigating the fabrication, tuning of catalytic properties and synergetic effects

Tailoring the structures of catalysts and the arrangement of organic bimetallic catalysts are essential in both fundamental research and applications. However, they still impose enormous challenges such as size and active species distribution, ordered uniformity, and controllable composition, which are critical in determining their specific activities and efficiency. Herein, a novel terpyridine-based hetero-bimetallic Ni/Pd nanosheet supported on graphene oxide (denoted as GO@Tpy-Ni/Pd) was fabricated, which exhibited higher catalytic activity, substrate applicability and recyclability for the Suzuki coupling reaction under mild conditions. The catalytic mechanism was heterogeneous catalysis at the interface and the synergetic effect between Pd and Ni resulted in a little Ni(0)/Pd(0) cluster including Pd(ii)/Ni(ii) as a whole being formed through electron transfer on the catalytic surface. This phenomenon could be interpreted as the nanoscale clusters of Ni/Pd being the real active centre stabilized by the ligand and GO and the synergetic effect. The absorption and desorption of different substrates and products on Ni/Pd clusters, as calculated by DFT, was proved to be another key factor.

The synergistic effect between Ni and Pd atom was the crucial factor for enhancing catalytic activity.