Ring-opening metathesis (ROM) of various unsaturated, constrained bicyclic ring systems has been investigated with the use of commercial ruthenium-based catalysts. Starting from various cyclodienes, the corresponding derived bicyclic lactone, lactam, and isoxazoline derivatives were submitted to ROM under ethenolysis. These functionalized, strained bicyclic systems afforded novel highly-functionalized diolefinated heterocyclic scaffolds in ROM reactions with stereocontrol, through the conservation of the configuration of the stereogenic centers of the starting compounds.
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http://dx.doi.org/10.3762/bjoc.14.247 | DOI Listing |
Langmuir
December 2024
Department of Chemistry, Carnegie Mellon University, 4400 Avenue, Pittsburgh, Pennsylvania 15213, United States.
Structurally tailored and engineered macromolecular (STEM) networks are attractive materials for soft robotics, stretchable electronics, tissue engineering, and 3D printing due to their tunable properties. To date, STEM networks have been synthesized by atom transfer radical polymerization (ATRP) or the combination of reversible addition-fragmentation chain-transfer (RAFT) polymerization and ATRP. RAFT polymerization could have limited selectivity with ATRP inimer sites that can participate in radical-transfer processes.
View Article and Find Full Text PDFChemistry
December 2024
Universiteit Utrecht, Chemistry, Universiteitsweg 99, 3584CG, Utrecht, NETHERLANDS, KINGDOM OF THE.
Nickelacyclobutanes are reactive intermediates in catalytic cycles involving cyclopropanation and insertion reactions. The stoichiometric study of these intermediates has shown that their reactivity is highly influenced by the coordination environment of the nickel center. A pentacoordinated nickelacyclobutane embedded in a diphosphine pincer ligand has been shown to selectively undergo various reactions with exogenous ligands, including [2+2] cycloreversion and carbene transfer to an isocyanide.
View Article and Find Full Text PDFMolecules
December 2024
Dipartimento di Scienza e Alta Tecnologia, Università degli Studi dell'Insubria, Via Valleggio 9, 22100 Como, Italy.
The coupling between bis(2-oxazolines) and two equivalents of aromatic aldehydes in the presence of catalytic amounts of NiCl affords an ester-imine product in synthetically useful yields. This virtually unknown, 100% atom-economic transformation involves the formal metathesis between the C=N double bond of the bis(2-oxazoline) moiety, which undergoes ring-opening, and the C=O double bond of the aldehyde. The scope of this transformation is studied, and a mechanism is proposed based on DFT calculations.
View Article and Find Full Text PDFJ Am Chem Soc
December 2024
Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory of Rare-Earth Materials Chemistry and Applications & Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
Activation and transformation of inert C-C bonds within arenes are challenging and important topics in synthetic chemistry. While there have been some reports on the activation of C-C bonds in arene rings, the realm of metathesis reactions involving arene C-C bonds remains unexplored. Here, we report a rare-earth metal-enabled intramolecular metathesis reaction of one benzene C-C bond and another C-C single bond, assisted by the high reactivity and unique synergistic effect of rare-earth metallacycles.
View Article and Find Full Text PDFNature
December 2024
Department of Chemistry, University of Basel, Basel, Switzerland.
Aromatic compounds are used across chemistry and materials science as a result of their stability, characteristic interactions, defined molecular shape and the numerous synthetic approaches for their synthesis by a diversity of cyclization reactions. In contrast, the cleavage of inert aromatic carbon-carbon bonds remained largely unfeasible due to the unfavourable energetics of disrupting aromaticity on ring opening. For non-aromatic structures, alkene metathesis catalysed by transition metal alkylidenes is established as one of the most versatile carbon-carbon bond-forming and breaking reactions.
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