Palladium-Catalyzed Synthesis of Alkylated Amines from Aryl Ethers or Phenols

Synthesis of alkylated amines is an important and attractive task in organic chemistry. Herein, we demonstrate a general protocol to produce alkylated amines via the catalytic coupling of amines with aromatic ethers or phenols. This transformation is performed in the presence of a heterogeneous palladium catalyst, and the key to its success is the use of a Lewis acid (LA) co-catalyst. This method shows broad substrate scope and a variety of phenols, including lignin-derived fragments, can be converted to the desired products smoothly. Preliminary mechanistic investigations reveal that this straightforward domino transformation occurs via a hydrogenolysis/reduction/condensation/reduction process

Direct Catalytic N‑Alkylation of Amines with Carboxylic Acids

A straightforward process for the N-alkylation of amines has been developed applying readily available carboxylic acids and silanes as the hydride source. Complementary to known reductive aminations, effective C–N bond construction proceeds under mild conditions and allows obtaining a broad range of alkylated secondary and tertiary amines, including fluoroalkyl-substituted anilines as well as the bioactive compound Cinacalcet HCl

Relay Iron/Chiral Brønsted Acid Catalysis: Enantioselective Hydrogenation of Benzoxazinones

An asymmetric hydrogenation reaction of benzoxazinones has been accomplished via a relay iron/chiral Brønsted acid catalysis. This approach provides a variety of chiral dihydrobenzoxazinones in good to high yields (75–96%) and enantioselectivities (up to 98:2 er). It is noteworthy that challenging 3-alkyl-substituted substrates underwent highly enantioselective reduction. A key to success is the utilization of a nonchiral phosphine ligand to reduce disadvantageous background reactions through tuning the catalytic activity of Fe₃(CO)₁₂

General and Selective Copper-Catalyzed Reduction of Tertiary and Secondary Phosphine Oxides: Convenient Synthesis of Phosphines

Novel catalytic reductions of tertiary and secondary phosphine oxides to phosphines have been developed. Using tetramethyldisiloxane (TMDS) as a mild reducing agent in the presence of copper complexes, PO bonds are selectively reduced in the presence of other reducible functional groups (FGs) such as ketones, esters, and olefins. Based on this transformation, an efficient one pot reduction/phosphination domino sequence allows for the synthesis of a variety of functionalized aromatic and aliphatic phosphines in good yields

Hydrogenation of Esters Catalyzed by Bis(<i>N</i>‑Heterocyclic Carbene) Molybdenum Complexes

A series of Mo complexes bearing inexpensive bidentate bis­(NHC) ligands have been synthesized and characterized by NMR and IR spectroscopy as well as single crystal XRD analysis. These complexes proved to be efficient for the catalytic hydrogenation of aliphatic and aromatic esters (>35 examples) operating at low catalyst loadings (0.5–2 mol %) and temperatures (80–120 °C). Various functional groups, e.g., CC double bonds, nitriles, alcohols, tertiary amines, halides, and acetals, as well as heteroaromatic substrates, lactones, and diesters, are tolerated by the optimal catalyst system. Based on NMR spectroscopic investigations, control experiments and DFT computations a non-bifunctional outer-sphere hydrogenation mechanism is proposed

Catalytic N‑Alkylation of Amines Using Carboxylic Acids and Molecular Hydrogen

A convenient, practical and green N-alkylation of amines has been accomplished by applying readily available carboxylic acids in the presence of molecular hydrogen. Applying an in situ formed ruthenium/triphos complex and an organic acid as cocatalyst, a broad range of alkylated secondary and tertiary amines are obtained in good to excellent yields. This novel method is also successfully applied for the synthesis of unsymmetrically substituted N-methyl/alkyl anilines through a direct three-component coupling reaction of the corresponding amines, carboxylic acids, and CO₂ as a C₁ source

Hydrogenation of Esters Catalyzed by Bis(<i>N</i>‑Heterocyclic Carbene) Molybdenum Complexes

A series of Mo complexes bearing inexpensive bidentate bis­(NHC) ligands have been synthesized and characterized by NMR and IR spectroscopy as well as single crystal XRD analysis. These complexes proved to be efficient for the catalytic hydrogenation of aliphatic and aromatic esters (>35 examples) operating at low catalyst loadings (0.5–2 mol %) and temperatures (80–120 °C). Various functional groups, e.g., CC double bonds, nitriles, alcohols, tertiary amines, halides, and acetals, as well as heteroaromatic substrates, lactones, and diesters, are tolerated by the optimal catalyst system. Based on NMR spectroscopic investigations, control experiments and DFT computations a non-bifunctional outer-sphere hydrogenation mechanism is proposed

Highly Chemoselective Metal-Free Reduction of Phosphine Oxides to Phosphines

Unprecedented chemoselective reductions of phosphine oxides to phosphines proceed smoothly in the presence of catalytic amounts of specific Brønsted acids. By utilizing inexpensive silanes, e.g., PMHS or (EtO)₂MeSiH, other reducible functional groups such as ketones, aldehydes, olefins, nitriles, and esters are well-tolerated under optimized conditions

Selective Semihydrogenation of Alkynes with N‑Graphitic-Modified Cobalt Nanoparticles Supported on Silica

For the first time N-graphitic-modified cobalt nanoparticles (Co/phen@SiO₂-800) are shown to be active in the semihydrogenation of alkynes to alkenes. Key to success for efficient catalysis is both the modification of the metal nanoparticles by nitrogen-doped graphitic layers and the use of silica as support. Several internal alkynes are converted to the <i>Z</i> isomer in high yields with up to 93% selectivity. In addition, a variety of terminal alkynes, including sensitive functionalized compounds, are readily converted into terminal alkenes. Notably, this non-noble-metal catalyst allows for the purification of alkenes by selective hydrogenation of the corresponding alkyne in the presence of an excess of olefin

Correction to “Synthesis and Characterization of Iron–Nitrogen-Doped Graphene/Core–Shell Catalysts: Efficient Oxidative Dehydrogenation of <i>N</i>‑Heterocycles”

Correction to “Synthesis and Characterization of Iron–Nitrogen-Doped Graphene/Core–Shell Catalysts: Efficient Oxidative Dehydrogenation of <i>N</i>‑Heterocycles