Synergistic Dinuclear Rhodium Induced Rhodium-Walking Enabling Alkene Terminal Arylation: A Theoretical Study

Rhodium(i)-catalyzed cascade C(sp2)-H bond alkylation - amidation of anilines: phosphorus as traceless directing group

We introduce a versatile Rh(i)-catalyzed cascade reaction, combining C(sp2)-H bond functionalization and amidation between N-arylphosphanamines and acrylates. This innovative approach enables the rapid synthesis of dihydroquinolinone scaffolds, a common heterocycle found in various pharmaceuticals. Notably, the presence of the phosphorus atom facilitates the aniline ortho-C(sp2)-H bond activation prior to N-P bond hydrolysis, streamlining one-pot intramolecular amidation. Moreover, we demonstrate the applicability of this reaction by synthesizing an antipsychotic drug. Detailed mechanistic investigations revealed the involvement of a Rh-H intermediate, with substrate inhibition through catalyst saturation.

High-Valent Pyrazolate-Bridged Platinum Complexes: A Joint Experimental and Theoretical Study

Complexes [{Pt(C^C*)(μ-pz)}₂] (HC^C*_A = 1-(4-(ethoxycarbonyl)phenyl)-3-methyl-1H-imidazol-2-ylidene 1a, HC^C*_B = 1-phenyl-3-methyl-1H-imidazol-2-ylidene 1b) react with methyl iodide (MeI) at room temperature in the dark to give compounds [{Pt^IV(C^C*)Me(μ-pz)}₂(μ-I)]I (C^C*_A2a, C^C*_B2b). The reaction of 1a with benzyl bromide (BnBr) in the same conditions afforded [Br(C^C*_A)Pt^III(μ-pz)₂Pt^III(C^C*_A)Bn] (5a), which by heating in BnBr(l) became [{Pt^IV(C^C*_A)Bn(μ-pz)}₂(μ-Br)]Br (6a). Experimental investigations and density functional theory (DFT) calculations on the mechanisms of these reactions from 1a revealed that they follow a S_N2 pathway in the two steps of the double oxidative addition (OA). Based on the DFT investigations, species such as [(C^C*_A)Pt^III(μ-pz)₂Pt^III(C^C*_A)R]X (RX = MeI Int-Me, BnBr Int-Bn) and [(C^C*_A)Pt^II(μ-pz)₂Pt^IV(C^C*_A)(R)X] (RX = MeI Int′-Me, BnBr Int′-Bn) were proposed as intermediates for the first and the second OA reactions, respectively. In order to put the mechanisms on firmer grounds, Int-Me was prepared as [(C^C*_A)Pt^III(μ-pz)₂Pt^III(C^C*_A)Me]BF₄ (3a′) and used to get [I(C^C*_A)Pt^III(μ-pz)₂Pt^III(C^C*_A)Me](4a), [(C^C*_A)Pt^II(μ-pz)₂Pt^IV(C^C*_A)(Me)I](Int′-Me), and [{Pt^IV(C^C*)Me(μ-pz)}₂(μ-I)]BF₄ (2a′). The single-crystal X-ray structures of 2a, 2b, 3a′, and 5a along with the mono- and bi-dimensional ¹H and ¹⁹⁵Pt{¹H} NMR spectra of all the named species allowed us to compare structural and spectroscopic data for high-valent complexes with the same core [{Pt(C^C*)(μ-pz)}₂] but different oxidation states.

Experimental and theoretical investigations on the mechanisms of OA reactions of MeI and BnBr to [{Pt^II(C^C*)(μ-pz)}₂] allowed us to get high-valent pyrazolate-bridged platinum compounds: Pt₂(III,III), Pt₂(II,IV), and Pt₂(IV,IV). Their stability and structural and spectroscopic features have been compared.

Density Functional Theory Study of Gold-Catalyzed 1,2-Diarylation of Alkenes: π-Activation versus Migratory Insertion Mechanisms

Density functional theory calculations are carried out to better understand the first gold-catalyzed 1,2-diarylation reactions of alkenes reported in the recent literature. The calculations on two representative reactions, aryl alkene/aryl iodide coupling pair (the aryl-I bond is located outside the aryl alkene) versus iodoaryl alkene/indole coupling pair (the aryl-I bond is located in the aryl alkene), confirm that the reaction involves a π-activation mechanism rather than the general migratory insertion mechanism in previously known metal catalysis by Pd, Ni, and Cu complexes. Theoretical results rationalize the regioselectivity of the reactions controlled by the aryl-I bond position (intermolecular or intramolecular) and also the ligand and substituent effects on the reactivity.

Ir-Catalyzed Remote Functionalization by the Combination of Deconjugative Chain-Walking and C-H Activation Using a Transient Directing Group

An Ir-catalyzed reaction of N-benzylideneanilines with functionalized alkenes such as α,β-unsaturated esters gave ortho-substituted benzaldehyde derivatives with a functional group at the remote position after acidic treatment. The present transformation involves deconjugative long-range isomerization (chain-walking) up to 11 times and C-H activation using an imino group as a transient directing group.

Site-selective C-H functionalization to access the arene backbone of indoles and quinolines

The site-selective C-H bond functionalization of heteroarenes can eventually provide chemists with great techniques for editing and building complex molecular scaffolds. During the past decade, benzo-fused N-heterocycles such as indoles and quinolines have been among the most widely investigated organic templates. Early developments have led to site-selective C-H bond functionalization on the pyrrole and pyridine cores of indoles and quinolines; however, C-H functionalization on the benzenoid ring has remained a great challenge in catalysis. In this review, we elaborate on recent developments in the highly challenging functionalization of C-H bonds on the less-reactive benzenoid core of indoles and quinolines. These findings are mainly described as selective directing group assisted strategies, remote C-H functionalization techniques and their reaction mechanisms. The underlying principle in each strategy is elucidated, which aims to facilitate the design of a more advanced structure of heterocycles based on bioactive molecules, synthetic drugs, and material aspects. Moreover, the challenges and perspectives for catalytic C-H functionalization to access the arene backbone of indoles and quinolines are also proposed in the conclusion section.

Oxymetalation or oxidative cyclization? mechanism of Pd-catalyzed annulation of enynones

Enynones are powerful synthons for constructing furan derivatives in the presence of transition metal catalysts. Unlike the conventional intramolecular nucleophilic attack with the activation of coinage metals, we propose that enynones undergo an oxidative cyclization process with a Pd(0) species. The full catalytic cycle involves oxidative cyclization, isocyanide insertion, and reductive elimination, which was supported by DFT calculations. Geometric and electronic analyses confirmed the oxidative cyclization process, which proceeds via a Pd(ii) intermediate.