Highly Chemoselective Access to 2,2′-Diaminobiaryls via Ni-Catalyzed Protecting-Group-Free Coupling of 2-Haloanilines

Palladium-Catalyzed Annulation Reaction of Bay-Diiodinated Arenes with o-Chloroaromatic Carboxylic Acids to Access Polycyclic Aromatic Compounds

A palladium-catalyzed annulation reaction of bay-diiodinated arenes with o-chloroaromatic carboxylic acids was established. This approach enables the synthesis of a variety of polycyclic aromatic compounds, especially polyalkoxy-substituted polycyclic aromatic compounds, frequently found in discotic liquid-crystalline materials. The investigations indicate that the product 2,3,8,9,12,13-hexakis(hexyloxy)-5-azadibenzo[fg,op]tetracene demonstrates favorable room-temperature liquid-crystalline properties.

Ni-Catalyzed Protecting Group Free Diphenic Acid Analog Synthesis

Severe side effects and drug resistance are major drawbacks of Pt-based chemotherapy in clinical practice, leading to the search for new Pt-based drugs through the tuning of coordination ligands. Therefore, seeking appropriate ligands has attracted significant interest in this area. In this study, we report a Ni-catalyzed coupling strategy for the divergent synthesis of diphenic acid derivatives and the application of these newly prepared acids in Pt(II) agent synthesis.

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.

Highly Chemoselective Ni-Catalyzed Protecting-Group-Free 2,2'-Biphenol Synthesis and Mechanistic Insights

The utilization of readily available starting materials to produce useful molecules is often challenged by selectivity issues. In this study, a Ni-catalyzed protecting-group-free C-C coupling protocol is described for the efficient synthesis of 2,2'-biphenol derivatives. Its remarkable chemoselectivity control ability, wide substrate scope, and excellent functional group tolerance highlight this newly developed strategy. Detailed mechanistic studies have demonstrated that potassium tert-butoxide acts as a critical agent to prevent the occurrence of protonation events.

Mechanism and Origin of Stereoselectivity of Ni-Catalyzed Cyclization/Carboxylation of Bromoalkynes with CO2

Bromoalkynes play important roles in coupling reactions because they can show obvious stereoselectivity to form E- and Z-isomers when substituents are different. However, the origin of the stereoselectivity in the bromoalkynes reaction is still unclear. Density functional theory (DFT) calculations were performed to provide an in-depth study of the reaction mechanism, clarifying the mechanistic details of the main reaction and the origin of the stereoselectivity. By comparing the syn-insertion mechanism of alkynes and the radical pathway, it is indicated that the electrostatic effect caused by the different charge distributions of the reactants is the main reason that Ni(I) species are more prone to syn-insertion of alkynes than Ni(II) species. In addition, the lower reaction energy barrier in the radical pathway suggests that it is more advantageous in terms of kinetics. The bond between Ni(I) species and alkenylation products has two directions to generate products of different configurations, which are the direct stereoselectivity-determining stages. The distortion/interaction analysis shows that the distortion energy mainly affects the product configuration, and the steric hindrance is the main factor controlling the stereoselectivity.

Theoretical study of NiI-NiIII cycle mediated by heterogeneous zinc in C-N cross-coupling reaction

Photoredox/transition-metal dual catalysis could efficiently construct C-N bonds by a cross-coupling reaction. The limitations of low recovery, low utilization rate and high cost have hindered the application and development of low-cost and efficient transition metal catalytic cycles. The integration of heterogeneous metal and transition metal catalysis is an appealing alternative to realize the oxidation state modulation of active species. With the support of density functional theory (DFT) calculation, we have explored the mechanistic details of Ni-catalyzed C-N cross-coupling of aryl bromide and cyclic amine assisted by zinc powder. Zinc successfully regulates the oxidation state of Ni^II → Ni^I, thus achieving the Ni^I-Ni^III-Ni^I catalytic cycle in the absence of light. In comparison, when the Ni(0) complex is employed as the initial catalyst, organic zinc reagents can still be involved in the transmetalation process to accelerate the cross-coupling reaction. We hope that such computational studies can provide theoretical reference for the design and development of low-cost and efficient catalytic systems for C-N cross-couplings.

Electrochemical Organic Synthesis of Electron-Rich Biaryl Scaffolds: An Update

Biaryl scaffolds are widely spread in biologically important natural products, in numerous therapeutic agents, but they are also considered a privileged class of ligands and (organo)catalysts; therefore, the development of efficient alternative methodologies to prepare such compounds is always attracting much attention. The present review discusses the organic electrosynthesis of biaryls starting from phenols, anilines, naphthols, and naphthylamines. The most significant examples of the works reported in the last decade are presented and classified according to the single class of molecules: after the introduction, the first three sections relate to the reactions of phenols, naphthols, and anilines, respectively; the other two sections refer to cross-coupling and miscellaneous reactions.

Synthesis of Tribenzo[b,d,f]azepines via Palladium-Catalyzed Annulation Reaction of 2-Iodobiphenyls with 2-Halogenoanilines

A palladium-catalyzed annulation reaction of 2-iodobiphenyls with 2-halogenoanilines has been developed. A variety of 2-iodobiphenyls and 2-halogenoanilines can undergo this transformation. Diversified tribenzo[b,d,f]azepine derivatives can be synthesized in moderate to excellent yields according to this method.

Synthesis of Axially Chiral 2,2'-Bisphosphobiarenes via a Nickel-Catalyzed Asymmetric Ullmann Coupling: General Access to Privileged Chiral Ligands without Optical Resolution

We report an asymmetric homocoupling of ortho-(iodo)arylphosphine oxides and ortho-(iodo)arylphosphonates resulting in highly enantioenriched axially chiral bisphosphine oxides and bisphosphonates. These products are readily converted to enantioenriched biaryl bisphosphines without need for chiral auxiliaries or optical resolution. This provides a practical route for the development of previously uninvestigated atroposelective biaryl bisphosphine ligands. The conditions have also proven effective for asymmetric dimerization of other, non-phosphorus-containing aryl halides.