A highly general, active, and stable catalytic system was realized in the palladium-catalyzed Suzuki-Miyaura reactions of sterically hindered aryl bromides with arylboronic acids using biphenylene-substituted di-tert-butylruthenocenylphosphine (R-Phos) as a supporting ligand.
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http://dx.doi.org/10.1021/jo900550g | DOI Listing |
Inorg Chem
December 2024
Polymer Science and Engineering Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India.
Metal complexes with tunable ligands play a crucial role in olefin polymerization and impart control over molecular weight, crystallinity, and stereoregularity. We report the single-step synthesis of imine-phenoxy ligands in excellent yields (81-93%). The identity of electronically tuned imine-phenoxy ligands was unambiguously ascertained by using a combination of spectroscopic and analytical methods.
View Article and Find Full Text PDFJ Am Chem Soc
December 2024
EaStCHEM, School of Chemistry, University of St Andrews, North Haugh, St. Andrews, KY16 9ST, U.K.
The [1,2]-rearrangement of allylic ammonium ylides is traditionally observed as a competitive minor pathway alongside the thermally allowed [2,3]-sigmatropic rearrangement. Concerted [1,2]-rearrangements are formally forbidden, with these processes believed to proceed through homolytic C-N bond fission of the ylide, followed by radical-radical recombination. The challenges associated with developing a catalytic enantioselective [1,2]-rearrangement of allylic ammonium ylides therefore lie in biasing the reaction pathway to favor the [1,2]-reaction product, alongside controlling a stereoselective radical-radical recombination event.
View Article and Find Full Text PDFJ Org Chem
December 2024
Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada.
Site-selective -arylations of glycoside-derived diols have been achieved by couplings with bromoarenes upon irradiation with blue LEDs in the presence of an iridium photocatalyst and a nickel complex. The use of hexamethylenetetramine (hexamine) in place of quinuclidine, along with the application of a methoxy-substituted 2,2'-bipyridine ligand, provided improvements in yield for this relatively challenging substrate class. Selective arylation took place at the less sterically hindered OH group, as determined by the substitution pattern and configuration of the glycoside substrate.
View Article and Find Full Text PDFOrg Lett
December 2024
School of Science, Faculty of Engineering and Science, University of Greenwich, Chatham, Kent ME4 4TB, U.K.
Traditional etherification methods, although staples in synthetic chemistry, often fall short in the efficient construction of sterically hindered dialkyl ethers, especially under mild and practical conditions. Recent advances have attempted to address these limitations, typically relying on transition metal catalysts, external reductants, or harsh reaction conditions. In this work, we disclose a novel electrochemical approach that enables the synthesis of sterically hindered ethers from economically relevant and readily accessible alcohols without the need for sacrificial oxidants.
View Article and Find Full Text PDFJ Am Chem Soc
December 2024
Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States.
Many terpene glycosides exhibit contrasteric patterns of 1,2-diol glycosylation in which the more hindered alcohol bears a sugar; protection of the less hindered alcohol only increases steric repulsion. Here, we report a method for contrasteric glycosylation using a new sugar-linker that forms a cleavable, 10-membered ring with high efficiency, leading to syntheses of cotylenin E, J, and ISIR-050. Linker selection was aided by DFT calculations of side reactions and stereoselectivity, as well as conformational analyses using autoDFT, a Python script that converts SMILES strings to DFT-optimized conformational ensembles.
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