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An NHC (N-heterocyclic carbene) catalyzed [3 + 3] annulation of δ-acetoxy allenoates and enaminones has been developed. This strategy provides a facile and convenient approach for the synthesis of 1,4-dihydropyridine and 3,4-dihydropyridine-based hexahydroquinoline derivatives (51 examples, up to 77% yield). This protocol features a broad substrate scope, good functional group tolerance, and mild reaction conditions. Interestingly, the regioselectivity of products is time-controlled. At the beginning of the reaction, 1,4-dihydropyridines are rapidly formed, and 3,4-dihydropyridines are obtained with the extension of the reaction time.
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http://dx.doi.org/10.1021/acs.joc.5c00685 | DOI Listing |
Chem Commun (Camb)
September 2025
Institut für Anorganische und Analytische Chemie, Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig, Germany.
N-Heterocyclic carbene complexes of alkali metals (M = Na, K, Rb, Cs) were prepared from the zwitterionic trimethylsilylimidazolium borate [(CF)B(IDipp)SiMe] (1) by reaction with the corresponding alkali metal -butoxides MOBu. The alkali metal complexes were isolated as tetrahydrofuran (THF) solvates of the type [(CF)B(IDipp)M(THF), 2M(THF), and their molecular structures were determined by single-crystal X-ray diffraction analysis.
View Article and Find Full Text PDFChem Soc Rev
September 2025
Department of Chemistry and Biochemistry, UCSD-CNRS Joint Research Laboratory (IRL3555), University of California, San Diego, La Jolla, CA 92093-0358, USA.
N-Heterocyclic carbenes (NHCs) hold a unique significance in organometallic catalysis and are powerful organocatalysts for a variety of organic transformations involving crucial intermediates such as Breslow intermediates (BIs), deprotonated BIs (BI-s), ketyl radicals (KRs), and acyl azoliums (AAs). To address the remaining challenges facing reactions catalyzed by NHCs, non-classical stable carbenes, namely 1,2,3-triazolylidenes (MICs), cousins of NHCs, have shown great potential. MICs share similar features with typical NHCs but possess unique characteristics, such as enhanced σ-donor ability and absence of dimerization.
View Article and Find Full Text PDFChem Rec
September 2025
Department of Chemistry, St. Thomas College Palai, Arunapuram P.O., Kottayam, Kerala, 686574, India.
An α-aryl-substituted enantioenriched ketone is a valuable building block for the production of both natural and medicinal compounds. Research into their asymmetric synthesis can be challenging yet rewarding because of the need to control regio-, chemo-, and enantioselectivity carefully. A wide range of catalytic strategies has been developed during the past three decades to gain access to these favored motifs.
View Article and Find Full Text PDFJ Am Chem Soc
September 2025
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, United States.
We report the first paramagnetic boron tetraradical, comprising four boraphenanthrene-type units with boryl radical centers bridged by a central tetraphenylethene (TPE) linker. With strongly π-accepting and sterically demanding cyclic(alkyl)(amino) carbene ligands (), spin densities localize on the boron-carbene fragments (92%), consistent with a true boron-centered tetraradical. Magnetic measurements of reveal minimal spin-spin coupling, consistent with four noninteracting = 1/2 centers.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
September 2025
Inorganic Materials Chemistry, Ruhr University Bochum, Universitätsstr. 150, 44801, Bochum, Germany.
Lithium is the core material of modern battery technologies and fabricating the lithium-containing materials with atomic layer deposition (ALD) confers significant benefits in control of film composition and thickness. In this work, a new mononuclear N-heterocyclic carbene (NHC) stabilized lithium complex, [Li(NHC)(hmds)], is introduced as a promising precursor for ALD of lithium-containing thin films. Structural characterization is performed, comparing density functional theory (DFT) and single-crystal X-ray diffraction (SC-XRD), confirming a rare mononuclear structure.
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