Manganese(I)-Catalyzed β-Methylation of Alcohols Using Methanol as C1 Source

Highly selective β-methylation of alcohols was achieved using an earth-abundant first row transition metal in the air stable molecular manganese complex [Mn(CO)₂Br[HN(C₂H₄PⁱPr₂)₂]] 1 ([HN(C₂H₄PⁱPr₂)₂]=MACHO-ⁱPr). The reaction requires only low loadings of 1 (0.5 mol %), methanolate as base and MeOH as methylation reagent as well as solvent. Various alcohols were β-methylated with very good selectivity (>99 %) and excellent yield (up to 94 %). Biomass derived aliphatic alcohols and diols were also selectively methylated on the β-position, opening a pathway to “biohybrid” molecules constructed entirely from non-fossil carbon. Mechanistic studies indicate that the reaction proceeds through a borrowing hydrogen pathway involving metal–ligand cooperation at the Mn-pincer complex. This transformation provides a convenient, economical, and environmentally benign pathway for the selective C−C bond formation with potential applications for the preparation of advanced biofuels, fine chemicals, and biologically active molecules     

Maximizing the Number of Interfacial Sites in Single‐Atom Catalysts for the Highly Selective,Solvent‐Free Oxidation of Primary Alcohols

The solvent‐free selective oxidation of alcohols to aldehydes with molecular oxygen is highly attractive yet challenging. Interfacial sites between a metal and an oxide support are crucial in determining the activity and selectivity of such heterogeneous catalysts. Herein, we demonstrate that the use of supported single‐atom catalysts (SACs) leads to high activity and selectivity in this reaction. The significantly increased number of interfacial sites, resulting from the presence of individually dispersed metal atoms on the support, renders SACs one or two orders of magnitude more active than the corresponding nanoparticle (NP) catalysts. Lattice oxygen atoms activated at interfacial sites were found to be more selective than O₂ activated on metal NPs in oxidizing the alcohol substrate. This work demonstrates for the first time that the number of interfacial sites is maximized in SACs, providing a new avenue for improving catalytic performance by developing appropriate SACs for alcohol oxidation and other reactions occurring at metal–support interfacial sites.     

Selective Hydrogen Atom Abstraction through Induced Bond Polarization: Direct α‐Arylation of Alcohols through Photoredox,HAT, and Nickel Catalysis

The combination of nickel metallaphotoredox catalysis, hydrogen atom transfer catalysis, and a Lewis acid activation mode, has led to the development of an arylation method for the selective functionalization of alcohol α‐hydroxy C−H bonds. This approach employs zinc‐mediated alcohol deprotonation to activate α‐hydroxy C−H bonds while simultaneously suppressing C−O bond formation by inhibiting the formation of nickel alkoxide species. The use of Zn‐based Lewis acids also deactivates other hydridic bonds such as α‐amino and α‐oxy C−H bonds. This approach facilitates rapid access to benzylic alcohols, an important motif in drug discovery. A 3‐step synthesis of the drug Prozac exemplifies the utility of this new method.