N-Alkoxycarbonyl / carbamoylmethyl substituted 1H-imidazol-2-yliden-Pd (II) complexes (Cat-1-5) were used for the first time as catalysts in the Suzuki-Miyaura reaction between aryl bromides and arylboronic acids. All complexes screened were found to be excellent catalysts in the selected coupling between 4-bromobenzaldehyde and phenylboronic acid at room temperature. Cat-3 was shown to be the most efficient one and used for the optimisation of the reaction conditions and determining the substrate scope. The application of the optimised method provided a series of biaryls (3a-l) in excellent isolated yields. With these promising results the catalysts could be applied succesfully to some other classic cross-coupling reactions such as Sonogashira, Stille and Buchwald-Hartwig.
The use of manganese triacetate as an oxidant component in the C-4 arylations of 2-aryl-quinazoline 3-oxides with arylboronic acids is reported. The new protocol was applied to prepare new 2,4-diarylated quinazoline 3-oxides in good to high yields. The method was shown to tolerate various substituents on both aromatic rings, and no complications as deoxygenation and rearrangement to quinazolin-4(3H)-one was observed.
A series of air-stable NHC-Pd-PEPPSI-type complexes bearing unsymmetrical NHC ligand, with a phenyl group in its backbone, were synthesized in excellent yields (82%-94%). Air and moisture-stable complexes were characterized by using 1 H NMR, 13 C NMR, FT-IR spectroscopy, and HRMS techniques.Single-crystal X-ray diffraction method was used to determine the crystal and molecular structure of the complexes. The molecular structure adopts slightly distorted square planar geometry around the metal centre and was refined as an inversion twin. The complexes were screened for their catalytic activities in Heck-Mizoroki and Suzuki-Miyaura cross-coupling reactions. Heck-Mizoroki reaction between the various aryl/hetaryl bromides and styrenes occurred in good to excellent yields in DMF in the presence of NaOAc as a base with low catalyst loadings (0.5%). The reactions also occur in aqueous media (DMF-H 2 O) in high yields. The Suzuki-Miyaura reaction between various aryl/ hetaryl bromides and phenylboronic acids came off in excellent yields in DMF-H 2 O in the presence of K 2 CO 3 as a base with low catalyst loadings (0.1%) at room temperature.
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