Rhodium-Catalyzed ortho-Bromination of O-Phenyl Carbamates Accelerated by a Secondary Amide-Pendant Cyclopentadienyl Ligand

The Versatile and Strategic O-Carbamate Directed Metalation Group in the Synthesis of Aromatic Molecules: An Update

The aryl O-carbamate (ArOAm) group is among the strongest of the directed metalation groups (DMGs) in directed ortho metalation (DoM) chemistry, especially in the form Ar-OCONEt2. Since the last comprehensive review of metalation chemistry involving ArOAms (published more than 30 years ago), the field has expanded significantly. For example, it now encompasses new substrates, solvent systems, and metalating agents, while conditions have been developed enabling metalation of ArOAm to be conducted in a green and sustainable manner. The ArOAm group has also proven to be effective in the anionic ortho-Fries (AoF) rearrangement, Directed remote metalation (DreM), iterative DoM sequences, and DoM-halogen dance (HalD) synthetic strategies and has been transformed into a diverse range of functionalities and coupled with various groups through a range of cross-coupling (CC) strategies. Of ultimate value, the ArOAm group has demonstrated utility in the synthesis of a diverse range of bioactive and polycyclic aromatic compounds for various applications.

Mechanistic Study on Selenium- and Sulfur-Mediated Isomerization of Hydroxamic Acids

An in-depth computational study reveals the intriguing mechanism of the recently reported isomerization of hydroxamic acids into para-aminophenols catalyzed by phenylselenyl bromide under mild conditions. The computations not only align with the reported experimental data, effectively explaining observed phenomena such as para-selectivity but also shed light on crucial aspects of the reaction mechanism that establish limitations on the scope of the studied rearrangement. Additionally, a joint theoretical/experimental study was performed to examine the potency of the phenylsulfenyl bromide to mediate the reaction under the same conditions.

Di- and trinuclear sandwich complexes of a cross-conjugated fulvene

We report di- and trinuclear palladium sandwich complexes of cross-π-conjugated fulvenes. Structural and theoretical analysis revealed that a fulvene sandwich framework holds a metal-metal bonded moiety, where the dinuclear and trinuclear bonds feature strong donation and back-donation, respectively. The trinuclear fulvene sandwich complex undergoes a unique reversible extrusion of a Pd atom from inside to outside the sandwich framework.

Photoredox-catalyzed coupling of aryl sulfonium salts with CO2 and amines to access O-aryl carbamates

An efficient photoredox-catalyzed three-component coupling reaction of aryl sulfonium salts, carbon dioxide and amines has been developed for the first time. This reaction provides a new strategy for the synthesis of a range of valuable O-aryl carbamates from readily available arenes via a site-selective thianthrenation/carbamoyloxylation two-step process. Mild conditions, broad substrate scope and good functional group tolerance are the features of the transformation. The synthetic utility of the method was demonstrated by the late-stage modification of bioactive molecules and pharmaceuticals.

Native Amide-Directed C(sp3 )-H Amidation Enabled by Electron-Deficient RhIII Catalyst and Electron-Deficient 2-Pyridone Ligand

Trivalent group-9 metal catalysts with a cyclopentadienyl-type ligand (CpM^III ; M=Co, Rh, Ir, Cp=cyclopentadienyl) have been widely used for directed C-H functionalizations, albeit that their application to challenging C(sp³ )-H functionalizations suffers from the limitations of the available directing groups. In this report, we describe directed C(sp³ )-H amidation reactions of simple amide substrates with a variety of substituents. The combination of an electron-deficient Cp^E Rh catalyst (Cp^E =1,3-bis(ethoxycarbonyl)-substituted Cp) and an electron-deficient 2-pyridone ligand is essential for high reactivity.

How the electron-deficient Cp ligand facilitates Rh-catalyzed annulations with alkynes

The dominant factors for the CpX ligand effects (Cp* versus CpE) on the reactivity for alkyne insertion into cationic and neutral rhodacycles are identified based on energy decomposition analysis.

Rhodium(III)-Catalyzed Oxidative ortho-Olefination of Phenyl Carbamates with Alkenes: Elucidation of Acceleration Mechanisms by Using an Unsubstituted Cyclopentadienyl Ligand

It has been established that an unsubstituted cyclopentadienyl (Cp) Rh(III) complex is an effective catalyst for the oxidative ortho-olefination of phenyl carbamates with both acrylates and styrenes under mild conditions. In addition, diolefination of a protected BINOL (1,1'-binaphthalene-2,2'-diol) proceeded in high yields and disubstituted acrylates could participate in this catalysis. Experimental and theoretical mechanistic studies elucidated that an electron-deficient nature of the unsubstituted CpRh(III) complex accelerates both the electrophilic aryl C-H rhodation and the rate-limiting alkene insertion steps.