Pd complexes with diimine ligands were investigated as novel Pd catalysts for direct synthesis of diphenyl carbonate by oxidative carbonylation of phenol using carbon monoxide and air. Best efficiency was obtained by using a PdCl2(ArN=CH–)2 or PdCl2(ArN=CMe–)2/Mn(TMHD)3/(Ph3P=)2NBr system where TOF reached 8.08 and 8.00 mol-DPC/mol-Pd h, respectively. The efficiency was increased with increases in the CO pressure. 相似文献
2,5-Dimethoxy-2,5-dihydrofuran did not form the expected aldehydes when water-soluble rhodium-catalysts were used for the conversion with syngas. Instead of hydroformylation, hydrogenation was the main reaction path in water, where 2,5-dimethoxytetrahydrofuran and its hydrolysis product, succinic dialdehyde, were obtained. The formation of hydrogenation products indicates water in the coordination sphere of rhodium. This may provide us with information on the environment of an active metal in aggregated structures like micelles and vesicles which are gaining in importance in biphasic catalysis. 相似文献
In this paper we report a brief review of the palladium–catalyzed olefination and amination of aryl chlorides. Special emphasis
is given on the efficiency of known catalysts. Best turnover numbers (TON up to 40,000) known to date for Heck reactions are
displayed by palladacycle catalysts, e.g., 1 in the presence of salts as co–catalysts. Model studies show that the catalyst
productivity is strongly influenced by the nature of the added salt. In addition, the ability of mixtures of Pd(OAc)2 and phosphines to catalyze the reaction of styrene with 1–chloro–4–trifluoromethylbenzene was studied dependent on the Pd:P
ratio. It was found that apart from the palladacycle 1 a number of established phosphines permit efficient C–Cl activation.
Amination of aryl chlorides is also possible in the presence of palladacycles as catalyst precursors. Crucial for the success
of the C–N bond forming reaction is the use of potassium tert–butoxide as base and reaction temperatures > 120°C. Turnover
numbers up to 900 and yields up to 80% have been obtained for the amination of 1–chloro–4–trifluoromethylbenzene.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
Porous organic polymers have prospects as functional substrates for catalysis, with quite different molecular properties from inorganic substrates. Here we disclose for the first time that porous palladium(II)‐polyimines are excellent catalysts for cooperatively catalyzed and enantioselective cascade reactions. In synergy with a chiral amine co‐catalyst, polysubstituted cyclopentenes and spirocyclic oxindoles, including the all‐carbon quaternary stereocenter, were synthesized in high yields. High diastereo‐ and enantioselectivities were achieved for these dynamic kinetic asymmetric transformations (DYKAT) of enals with propargylic nucleophiles.
The CO/tert‐butylstyrene/ethylene terpolymerization catalyzed by Pd‐(N‐N′) complexes was studied. The results evidence that the olefin preferentially inserted in the terpolymer chain is strictly related to the nature of the nitrogen ligand, mainly to its steric constraints, and not to the kind of ligand. Indeed, slight variations in the backbone of the nitrogen ligands coordinated to palladium allow for the synthesis of terpolymers with a controlled composition. 相似文献
A binaphthyl‐supported Pd nanoparticles (Pd‐BNP)‐catalyzed aminocarbonylation of aryl iodides in the presence of carbon monoxide and amines for the synthesis of amides has been developed. This methodology provides an efficient route for the synthesis of a COX‐2 enzyme inhibitor having anti‐inflammatory activity.
