Mechanistic Insights into the Ru(II)-Catalyzed Intramolecular Formal [3 + 2] Cycloaddition of (<i>E</i>)-1,6-Enynes
作者:Rui Liu、Yajie Chou、Bing Lian、De-cai Fang、Ming Gao、Tanyu Cheng、Guohua Liu
DOI:10.1021/acs.orglett.9b02446
日期:2019.9.6
challenge in organic chemistry. Herein, we report a Ru(II)-catalyzed formal [3 + 2] cycloaddition as an efficient method to prepare unprecedented bicyclo[3.3.0]octenes from readily available (E)-1,6-enynes. Mechanistic studies based on the deuterium labeling experiments and the DFT calculation disclose a reasonable mechanistic pathway, where a ruthenacyclopentene generated by an ene-yne oxidative cyclization
alkyne proceeds smoothly at room temperature to afford highly substituted five-membered cycliccompounds featuring a 1,5-enyne motif. Deuterium-labeling experiments showed that the key ruthenacyclopentene intermediate undergoes cleavage of metal–carbon bonds through the metal-assisted σ-bond metathesis reaction, thus leading to the formation of C(sp2)–H and C(sp3)–C(sp) bonds.
Broad-Spectrum Catalysts for the Ambient Temperature Anti-Markovnikov Hydration of Alkynes
作者:Le Li、Mingshuo Zeng、Seth B. Herzon
DOI:10.1002/anie.201404320
日期:2014.7.21
Anti‐Markovnikov alkynehydration provides a valuable route to aldehydes. Half‐sandwich ruthenium complexes ligated by 5,5′‐bis(trifluoromethyl)‐2,2′‐bipyridine are remarkably active for this transformation. In the presence of 2 mol % metal, a wide range of functionalized aliphatic and aromatic alkynes are hydrated in high yield at ambienttemperature.
Palladium-catalyzed diastereo-differentiative tandem connection of cis-alkenyl iodide, cyclic fragment, and terminal acetylene was executed. The discrimination of the diastereotopic face and olefinic carbons of norbornene was achieved with accompanying isomerization of the cis-geometry of the olefin to trans in good yields.
In ring-closing metathesis (RCM) reactions of enynes, the substituents on the multiplebonds are quite important. Although RCM of an enyne having a monosubstituted alkene proceeds smoothly using the first-generation ruthenium-carbene complex 1a, that of an enyne having a disubstituted alkene and internal alkyne using 1a does not proceed. However, the second-generation ruthenium-carbene complex 1b or