48 research outputs found
Asymmetric transfer hydrogenation of acetophenone derivatives using 2-benzyl-tethered ruthenium (II)/TsDPEN complexes bearing Ī·6-(p-OR) (R = H, iPr, Bn, Ph) ligands
A series of 4ā²-OR (RāÆ=āÆH, iPr, Bn, Ph) substituted ruthenium (II) biphenyl TsDPEN complexes are described; the complexes are accessed via an operationally simple and reliable two-step ligand synthesis followed by ligation to the ruthenium (II) centre. We report the preliminary asymmetric transfer hydrogenation (ATH) results on a range of primarily acetophenone derivatives with these new complexes using FA/TEA (5:2) as a reducing agent; the results confirm that these catalysts are capable of reducing the substrates within 48āÆh with excellent enantioselectivities
Synthesis ofN,Nā²-Disubstituted Urea from Ethylene Carbonate and Amine Using CaO
Calcium oxide has been proved to be an excellent solid catalyst for the synthesis of N,Nā²-disubstituted ureas from ethylene carbonate and primary amines under mild conditions
<span style="font-size:11.0pt;mso-bidi-font-size: 10.0pt;font-family:"Times New Roman";mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-GB;mso-fareast-language:EN-US;mso-bidi-language:AR-SA" lang="EN-GB">Chitosan biohydrogel beads: A recyclable, biodegradable, heterogeneous catalyst for the regioselective synthesis of 5-aryl-2-oxazolidinones from carbon dioxide and aziridines at mild conditions</span>
1354-1360<span style="mso-bidi-font-size:9.0pt;color:black;
letter-spacing:-.1pt" lang="EN-GB">In the search for efficient catalysts for a reaction
under mild conditions, c<span style="mso-bidi-font-size:9.0pt;
letter-spacing:-.1pt" lang="EN-GB">ycloaddition reactions of carbon dioxide with various
aziridines catalyzed by chitosan biohydrogel beads without additional solvent
and metal co-catalyst to form
five-membered 5-aryl-2-oxazolidinones in high yields and selectivity has been
studied. Reaction rate, conversion and selectivity are studied as a function of
a series of input variables including catalyst loading, temperature, pressure
and solvent system. The catalyst is easily recovered and has been reused in
five consecutive cycles without any significant loss of its catalytic activity
and selectivity. The catalyst, chitosan biohydrogel beads, has been
characterized by a variety of techniques, namely, scanning electron microscopy and Fourier transform infrared
spectroscopy. A plausible reaction mechanism
for the hydrogen-bond assisted ring-opening of aziridine to five-membered
5-aryl-2-oxazolidinones is also proposed.
</span
Aminophosphine Palladium Pincer-Catalyzed Carbonylative Sonogashira and SuzukiāMiyaura Cross-Coupling with High Catalytic Turnovers
This work documents the first palladium
pincer complex-catalyzed
carbonylative Sonogashira (CS) and carbonylative SuzukiāMiyaura
(CSM) cross-coupling. Compared to previous protocols, which employ
hazardous and toxic solvents, the aminophosphine pincer complex {[C6H3-2,6-(NHPĀ{piperidinyl}2)2]ĀPdĀ(Cl)} (III) catalyzes both the cross-coupling reactions
in propylene carbonate, an eco-friendly and sustainable polar aprotic
solvent. Advantageously, employing III allows the CS
cross-coupling to be carried out at a palladium loading of 10ā4 mol % and the CSM cross-coupling to be carried out
at 10ā6 mol %, thus resulting in catalytic turnovers
of 105 and 107, respectively. Relative comparison
of the pincer complex with conventional palladium precursors PdĀ(OAc)2 and PdCl2(PPh3)2 shows the
efficiency and robustness of the pincer complex in effecting higher
catalytic activity at low palladium loadings
Synthesis of Ethylene Glycol from Syngas via Oxidative Double Carbonylation of Ethanol to Diethyl Oxalate and Its Subsequent Hydrogenation
This work reports a novel sustainable
two-step method for the synthesis
of ethylene glycol (EG) using syngas. In the first step, diethyl oxalate
was selectively synthesized via oxidative double carbonylation of
ethanol and carbon monoxide (CO) using a ligand-free, recyclable Pd/C
catalyst. In the second step, the diethyl oxalate produced underwent
subsequent hydrogenation using [2-(di-tert-butylphosphinomethyl)-6-(diethylaminomethyl)Āpyridine]ĀrutheniumĀ(II)
chlorocarbonyl hydride to get EG and ethanol. Thus, the generated
ethanol can be recycled back to the first step for double carbonylation.
This method gives a sustainable route to manufacture EG using carbon
monoxide and hydrogen
Selective Hydrogenation of Phenylacetylene with Graphite Intercalated Platinum Nanosheets
Platinum nanosheets between graphite layers were active for hydrogenation of ethynyl group of phenylacetylene but less active for that of aromatic rings of phenylacetylene and benzene due to its structural characteristics