'Pseudo-halide' Derivatives of Grubbs- and Schrock-Type Catalysts for Olefin Metathesis

摘要

Metathesis has persisted through the years as a formidable synthetic approach to various unsaturated organic molecules and macromolecules. The 21st century developments in olefin metathesis continue to feature more efficient and selective, well-defined metathesis catalysts. Due to the easily regulated steric and electronic properties of 'pseudo-halide' derivatives, their study has launched a new milestone in ruthenium- and molybdenum-based catalysis. Synthesizing 'pseudo-halide' derivatives often entails replacing halide ligands with easily modified carboxylates, perfluorocarboxylates, phenoxides, isocyanates, isothiocyanates, pyridines, nitrates, and trifluoromethanesulfonates. This account elucidates the recent advances in 'pseudo-halide'-containing olefin metathesis, including synthetic approaches to obtain new catalysts and op-timization of the ligand sphere. Several innovations in Ru- and Moalkylidenes that concern initiation efficiency, reactivity, stereoselectivity, supported catalysis, cyclopolymerization, and copolymerization are described. Refinement of the anionic 'pseudo-halide' ligands has enabled the perfection of Ru- and Mo-based metathesis catalysts in both reactivity and selectivity. These advances have led to stereoselectivity in polymerizations, improved copolymerization affinity, and the regioselective cyclopolymerization of 1,6-heptadiynes to result in conjugated polymers solely based on five-membered repeat units. 1Introduction 2Catalyst Synthesis 2.1Modified Ru-Alkylidene-Based Metathesis Catalysts 2.1.1 Halides, Alkoxides, and Aryloxides 2.1.2 Bidentate or Monodentate Carboxylates 2.1.3 Nitrates and Trifluoromethanesulfonates 2.1.4 Isocyanates and Isothiocyanates 2.2Modified Mo-Alkylidene-Based Metathesis Catalysts 2.2.1 Bidentate or Monodentate Carboxylates 2.3Supported Catalysts 3Characterization and Structural Effects 3.1General Procedures 3.2X-ray Structures 3.3~1H and~(13)C NMR Shifts of the Alkylidene Resonances 4Catalysis in Organic Synthesis 4.1Ring-Closing Metathesis (RCM) 4.2Other Metathesis Reactions 5Catalysis in Polymerization 5.1Ring-Opening Metathesis Polymerization (ROMP) 5.1.1 2-Norbornene (NBE) 5.1.2 Cyclooctene (COE) 5.1.3 cis-1,5-Cyclooctadiene (COD) 5.2Cyclopolymerization of 1,6-Heptadiynes 5.2.1 Diethyl Dipropargylmalonate (DEDPM) 5.2.2 Other 1,6-Heptadiynes 5.3Copolymerization 5.3.1 Copolymers via Ring-Opening Metathesis Polymerization (ROMP) 5.3.2 Copolymers of 1,6-Heptadiynes with Acetylene 6Summary and Outlook