acyclic ethers is accessed with very high functional group tolerance and excellent regioselectivity. A new organocatalytic protocol for the aerobic dehydrogenative allylation of alcohols using non-activatedalkenes as the allylating reagent and ambient air as the terminal oxidant is established. Mechanistically, the procedure relies on the interplay of a diselane and a photoredox catalyst by means of
cation‐π biocatalysis, reported here is the anion‐π‐catalyzed epoxide‐opening ether cyclizations of oligomers. Only on π‐acidicaromatic surfaces having a positive quadrupole moment, such as hexafluorobenzene to naphthalenediimides, do these polyether cascade cyclizations proceed with exceptionally high autocatalysis (rate enhancements kauto/kcat >104 m−1). This distinctive characteristic adds complexity
阴离子-π催化通过稳定芳香族π-表面上的阴离子过渡态而起作用,从而为分子转化提供了一种新方法。阴离子-π相互作用的离域性质表明,它们在稳定长距离电荷位移方面最有效。因此,针对与常规阳离子-π生物催化的类固醇环化一样具有魅力的阴离子级联反应,此处报道的是低聚物的阴离子-π催化的环氧化物-开环醚环化。仅在具有正四极矩的π酸性芳族表面上(例如六氟苯到萘二酰亚胺),这些聚醚级联环化才会进行极高的自催化作用(速率增强k auto / k cat > 10 4 m -1)。这种独特的特征增加了反应机理的复杂性(Goldilocks型底物浓度依赖性,以熵为中心的底物不稳定),并为未来的发展开辟了有趣的前景。
作者:Renee M. Thomas、Alexey Fedorov、Benjamin K. Keitz、Robert H. Grubbs
DOI:10.1021/om200911e
日期:2011.12.26
substituent on the NHC ligand of the ruthenium complex was found to inducelatent behavior toward cross-metathesis reactions, and exchange of the chloride ligands for iodide ligands was necessary to attain latent behavior during ring-opening metathesis polymerization (ROMP). Iodide-based catalysts showed no reactivity toward ROMP of norbornene-derived monomers at 25 °C and upon heating to 85 °C gave complete
Synthetic and Structural Peculiarities of Neutral and Cationic Molybdenum Imido and Tungsten Oxo Alkylidene Complexes Bearing Weakly Coordinating N‐Heterocyclic Carbenes
作者:Michael R. Buchmeiser、Dongren Wang、Roman Schowner、Laura Stöhr、Felix Ziegler、Suman Sen、Wolfgang Frey
DOI:10.1002/ejic.202400082
日期:2024.7
The syntheses of neutral and cationic molybdenumimido alkylidene N-heterocyclic carbene (NHC) complexes as well as of tungsten oxo alkylidene NHC complexes bearing electron-deficient NHCs together with structural peculiarities are reported. Benchmark olefin metathesis reactions revealed that the cationic molybdenumimido alkylidene complexes bearing weakly coordinating NHCs still display appreciable