Three types of Au(I) N-heterocyclic carbene (NHC) and imidazole (Im) complexes, namely [Au(NHC)Cl], [Au(NHC)(Im)][NO(3)], and [Au(NHC)(2)][NO(3)], with two-, three-, and four-N-long alkyl chains, respectively, were synthesized and their mesomorphic properties investigated. Only the [Au(NHC)(Im)][NO(3)] series of compounds, adopting an m-shaped conformation in the solid state, showed liquid crystalline properties. For the molecules with three alkyl chains in particular, the Coulombic and hydrogen bonding interactions between the cationic head core and anionic NO(3)(-), and the hydrophobic chain-chain interactions facilitate in sustaining the partially ordered motion, which is not observed for those with two and four arms. These complexes were employed for preparation of stable nanomaterials in organic solvents.
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http://dx.doi.org/10.1039/b907171g | DOI Listing |
Sci Bull (Beijing)
December 2024
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200032, China. Electronic address:
Divergent synthesis of valuable molecules through common starting materials and metal catalysis represents a longstanding challenge and a significant research goal. We here describe chemodivergent, highly enantio- and regioselective nickel-catalyzed reductive and dehydrogenative coupling reactions of alkynes, aldehydes, and silanes. A single chiral Ni-based catalyst is leveraged to directly prepare three distinct enantioenriched products (silyl-protected trisubstituted chiral allylic alcohols, oxasilacyclopentenes, and silicon-stereogenic oxasilacyclopentenes) in a single chemical operation.
View Article and Find Full Text PDFJ Am Chem Soc
January 2025
Institut für Chemie, Technische Universität Chemnitz, Straße der Nationen 62, 09111 Chemnitz, Germany.
We present a bifunctional catalyst consisting of a copper(I)/N-heterocyclic carbene and an organocatalytic guanidine moiety that enables, for the first time, a copper(I)-catalyzed reduction of amides with H as the terminal reducing agent. The guanidine allows for reactivity tuning of the originally weakly nucleophilic copper(I) hydrides - formed in situ - to be able to react with difficult-to-reduce amides. Additionally, the guanidine moiety is key for the selective recognition of "privileged" amides based on simple and readily available heterocycles in the presence of other amides within one molecule, giving rise to hitherto unknown site-selective catalytic amide hydrogenation.
View Article and Find Full Text PDFChem Commun (Camb)
January 2025
Institute of Organic Chemistry, Polish Academy of Sciences, 01-224 Warsaw, Kasprzaka 44/52, Poland.
We report the synthesis, isolation, and comprehensive characterization of N-heterocyclic carbene gold xanthate (NHC-Au-X, X - xanthate) complexes. These easily accessible complexes demonstrate significant versatility as photocatalysts, facilitating [2+2]-cycloadditions, and as π-catalysts in the intramolecular hydroxylation of allenes and hydrohydrazination of alkynes.
View Article and Find Full Text PDFNat Commun
January 2025
School of Chemistry, Chemical Engineering, and Biotechnology, Nanyang Technological University, Singapore, 637371, Singapore.
Acylation stands as a fundamental process in both biological pathways and synthetic chemical reactions, with acylated saccharides and their derivatives holding diverse applications ranging from bioactive agents to synthetic building blocks. A longstanding objective in organic synthesis has been the site-selective acylation of saccharides without extensive pre-protection of alcohol units. In this study, we demonstrate that by simply altering the chirality of N-heterocyclic carbene (NHC) organic catalysts, the site-selectivity of saccharide acylation reactions can be effectively modulated.
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