48 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 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
Toward a Practical Catalyst for Convenient Deaminative Hydrogenation of Amides under Mild Conditions
Amide
bond reduction is a versatile transformation offering
access
to various alcohols and amines that could be used as valuable precursors
in the chemical and pharmaceutical industries, e.g., for manufacturing
plastics, textiles, dyes, agrochemicals, etc. Over the last two decades,
catalytic amide hydrogenation employing homogeneous catalysis has
gained more attention due to the atom efficiency and low environmental
impact of this transformation. Owing to the inherent strength of amide
bonds, amide hydrogenation procedures often involve high temperatures
and pressures, which is why efforts are being channeled to finding
protocols with lower-energy input. Here, we report a mild amide hydrogenation
method involving commercially available precursors Ru(acac)3 and 1,2-bis(di-tert-butylphosphinomethyl)benzene
(L4), which under basic conditions, at 80 °C and
under 30 bar of H2, can selectively hydrogenate a series
of 2°-benzamides to anilines and alcohols with yields of 36–98%
and 29–92%, respectively. Additionally, 1°- and 3°-amides
proved to be appropriate substrates; however, low to moderate yields
were obtained. The catalyst is believed to operate via an inner-sphere
mechanism with a hemiaminal being the likely intermediate during the
hydrogenation process
Selective Hydrogenation of Ruthenium Acylphosphine Complexes
Hydrogenation
of a benzene ruthenium chloride dimer in the presence
of novel acylphosphine (phosphomide) ligands resulted in the
formation of corresponding ruthenium(II)–benzyl phosphine complexes.
Here, selective reduction of the carbonyl group to a methylene unit
takes place with molecular hydrogen under mild conditions in good
yield. This approach provides an alternative synthesis of ruthenium
phosphine complexes of benzyl and heterobenzyl phosphine ligands
Acrolein Hydrogenation on Ni(111)
Acrolein
hydrogenation via allyl alcohol, propanal, and enol into
propanol on the Ni(111) surface has been investigated using the spin-polarized
periodic density functional theory method. On the basis of the computed
adsorption energies and effective hydrogenation barriers, acrolein
hydrogenation into propanal and allyl alcohol obeys the Langmuir–Hinshelwood
mechanism and propanal formation is more favored kinetically and thermodynamically
than allyl alcohol formation. Hydrogenation of propanal and allyl
alcohol should follow the Eley–Rideal mechanism. The adsorption
energies of acrolein, allyl alcohol, and propanal along with the partial
hydrogenation selectivity on Ni, Au, Ag, and Pt catalysts have been
compared and discussed
Selective Hydrogenation of Ruthenium Acylphosphine Complexes
Hydrogenation
of a benzene ruthenium chloride dimer in the presence
of novel acylphosphine (phosphomide) ligands resulted in the
formation of corresponding ruthenium(II)–benzyl phosphine complexes.
Here, selective reduction of the carbonyl group to a methylene unit
takes place with molecular hydrogen under mild conditions in good
yield. This approach provides an alternative synthesis of ruthenium
phosphine complexes of benzyl and heterobenzyl phosphine ligands
Selective Palladium-Catalyzed Aminocarbonylation of 1,3-Dienes: Atom-Efficient Synthesis of β,γ-Unsaturated Amides
Carbonylation
reactions constitute important methodologies for
the synthesis of all kinds of carboxylic acid derivatives. The development
of novel and efficient catalysts for these transformations is of interest
for both academic and industrial research. Here, the first palladium-based
catalyst system for the aminocarbonylation of 1,3-dienes is described.
This atom-efficient transformation proceeds under additive-free conditions
and provides straightforward access to a variety of β,γ-unsaturated
amides in good to excellent yields, often with high selectivities
General and Regioselective Synthesis of Pyrroles via Ruthenium-Catalyzed Multicomponent Reactions
A general
and highly regioselective synthesis of pyrroles via ruthenium-catalyzed
three-component reactions has been developed. A variety of ketones
including less reactive aryl and alkyl substrates were efficiently
converted in combination with different type of amines and vicinal
diols into various substituted pyrroles in reasonable to excellent
isolated yields. Additionally, α-functionalized ketones gave
synthetically interesting amido-, alkoxy-, aryloxy-, and phosphate-substituted
pyrroles in a straightforward manner. The synthetic protocol proceeds
in the presence of a commercially available ruthenium catalyst system
and catalytic amount of base. It proceeds with high atom-efficiency
and shows a broad substrate scope and functional group tolerance,
making it a highly practical approach for preparation of various pyrrole
derivatives
Synthesis of <i>N</i>‑Lauroyl Sarcosine by Amidocarbonylation: Comparing Homogeneous and Heterogeneous Palladium Catalysts
An
improved system for the synthesis of <i>N</i>-acyl
amino acids via Pd-catalyzed amidocarbonylation is reported. Utilizing
inexpensive Pd black gives the industrially important surfactant <i>N</i>-lauroyl sarcosine in excellent yields (95%) on a multi-gram
scale. Advantages of the new system include reusability, decreased
process temperature, and, importantly, drastically decreased co-catalyst
loading
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 Fe<sub>3</sub>(CO)<sub>12</sub>