8 research outputs found
Selective Hydrogenation of Ruthenium Acylphosphine Complexes
Hydrogenation
of a benzene ruthenium chloride dimer in the presence
of novel acylÂphosphine (phosphomide) ligands resulted in the
formation of corresponding rutheniumÂ(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
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
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
Selective Hydrogenation of Ruthenium Acylphosphine Complexes
Hydrogenation
of a benzene ruthenium chloride dimer in the presence
of novel acylÂphosphine (phosphomide) ligands resulted in the
formation of corresponding rutheniumÂ(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 Carbonylation of Alkynes: An Atom-Economic Synthesis of 1,4-Dicarboxylic Acid Diesters
A class
of novel diphosphine ligands bearing pyridine substituents
was designed and synthesized for the first time. The resulting palladium
complexes of <b>L1</b> allow for chemo- and regioselective dialkoxycarbonylation
of various aromatic and aliphatic alkynes affording a wide range of
1,4-dicarboxylic acid diesters in high yields and selectivities. Kinetic
studies suggest the generation of 1,4-dicarboxylic acid diesters via
cascade hydroesterification of the corresponding alkynes. Based on
these investigations, the chemo- and regioselectivities of alkyne
carbonylations can be controlled as shown by switching the ligand
from <b>L1</b> to <b>L3</b> or <b>L9</b> to give
α,β-unsaturated esters
Palladium-Catalyzed Selective Generation of CO from Formic Acid for Carbonylation of Alkenes
A general
and selective palladium-catalyzed alkoxycarbonylation
of all kinds of alkenes with formic acid (HCOOH, FA) is described.
Terminal, di-, tri-, and tetra-substituted including functionalized
olefins are converted into linear esters with high yields and regioselectivity.
Key-to-success is the use of specific palladium catalysts containing
ligands with built-in base, e.g., <b>L5</b>. Comparison experiments
demonstrate that the active catalyst system not only facilitates isomerization
and carbonylation of alkenes but also promotes the selective decomposition
of HCOOH to CO under mild conditions
Ruthenium-Catalyzed Selective α,β-Deuteration of Bioactive Amines
A novel and convenient protocol for the catalytic hydrogen–deuterium
exchange of biologically active tertiary amines utilizing the borrowing
hydrogen methodology has been developed. In the presence of the readily
available Shvo catalyst, excellent chemoselectivity toward α-
and β-protons with respect to the nitrogen atom as well as high
degree of deuterium incorporation and functional group tolerance is
achieved. This allowed for the deuteration of complex pharmaceutically
interesting substrates, including examples for actual marketed drug
compounds. Notably, this method constitutes a powerful tool for the
generation of valuable internal standard materials for LC–MS/MS
analyses highly demanded for various life-science applications
Combining Isocyanides with Carbon Dioxide in Palladium-Catalyzed Heterocycle Synthesis: <i>N</i>3‑Substituted Quinazoline-2,4(1<i>H</i>,3<i>H</i>)‑diones via a Three-Component Reaction
We
report a Pd-catalyzed three-component reaction of 2-bromoanilines,
carbon dioxide, and isocyanides. The combination of these two readily
available C<sub>1</sub>-reactants, featuring a huge difference in
kinetic and thermodynamic stability, is hitherto unprecedented in
transition-metal catalysis. With this one-pot three-component reaction, <i><i>N</i></i>3-substituted quinazoline-2,4Â(1<i>H</i>,3<i>H</i>)-diones are obtained in moderate to
high yields in a completely regio- and chemoselective manner. Our
approach easily allows variation of the arene and <i>N</i>3-substitution pattern of the desired heterocycle. The formal synthesis
of different APIs illustrates its practical applicability. In addition,
the methodology also allows for a convenient and selective <sup>13</sup>C-labeling through the use of <sup>13</sup>CO<sub>2</sub>. This is
illustrated for [2-<sup>13</sup>C]-2,4-dichloro-6,7-dimethoxyquinazoline
synthesis, a key intermediate for several APIs