14 research outputs found
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 NâAlkylation 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 CâN 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 (75â96%) 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 Fe<sub>3</sub>(CO)<sub>12</sub>
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>âHeterocyclic Carbene) Molybdenum Complexes
A series of Mo complexes
bearing inexpensive bidentate bisÂ(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 (0.5â2
mol %) and temperatures (80â120 °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 NâAlkylation 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 CO<sub>2</sub> as a C<sub>1</sub> source
Hydrogenation of Esters Catalyzed by Bis(<i>N</i>âHeterocyclic Carbene) Molybdenum Complexes
A series of Mo complexes
bearing inexpensive bidentate bisÂ(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 (0.5â2
mol %) and temperatures (80â120 °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)<sub>2</sub>MeSiH, other reducible functional groups
such as ketones, aldehydes, olefins, nitriles, and esters are well-tolerated
under optimized conditions
Selective Semihydrogenation of Alkynes with NâGraphitic-Modified Cobalt Nanoparticles Supported on Silica
For the first time
N-graphitic-modified cobalt nanoparticles (Co/phen@SiO<sub>2</sub>-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 âSynthesis and Characterization of IronâNitrogen-Doped Graphene/CoreâShell Catalysts: Efficient Oxidative Dehydrogenation of <i>N</i>âHeterocyclesâ
Correction
to âSynthesis and Characterization
of IronâNitrogen-Doped Graphene/CoreâShell Catalysts:
Efficient Oxidative Dehydrogenation of <i>N</i>âHeterocycles