Controllable Isomerization of Alkenes by Dual Visible‐Light‐Cobalt Catalysis
作者:Qing‐Yuan Meng、Tobias E. Schirmer、Kousuke Katou、Burkhard König
DOI:10.1002/anie.201900849
日期:2019.4.16
We report herein that thermodynamic and kineticisomerization of alkenes can be accomplished by the combination of visible light with Co catalysis. Utilizing Xantphos as the ligand, the most stable isomers are obtained, while isomerizing terminal alkenes over one position can be selectively controlled by using DPEphos as the ligand. The presence of the donor–acceptor dye 4CzIPN accelerates the reaction
Asymmetric Cross-coupling of Potassium 2-Butenyltrifluoroborates with Aryl and 1-Alkenyl Bromides Catalyzed by a Pd(OAc)<sub>2</sub>/Josiphos Complex
作者:Yasunori Yamamoto、Shingo Takada、Norio Miyaura
DOI:10.1246/cl.2006.1368
日期:2006.12
The asymmetric cross-coupling reaction of [CH3CH=CHCH2BF3]K with aryl or 1-alkenyl bromides selectively occurred at the γ-carbon of 2-butenylborane moiety with regioselectivities in a range of 84–99%. The enantioselectivities were in a range of 77–90%ee when a palladium/CyPF-t-Bu complex was used at 80 °C in the presence of K2CO3 (3 equiv.) in H2O–MeOH (9/1).
Catalytic generation of alkyl radicals from aldehydes via oxidative deformylation was realized using a cobalt-salen complex with H2O2. The deformylation was thought to proceed through homolytic cleavage of peroxohemiacetal intermediates to provide even primary alkyl radicals under mild conditions. Variously substituted and functionalized hydroperoxides were obtained from corresponding aldehydes in good yield
Visible‐Light Controlled Divergent Catalysis Using a Bench‐Stable Cobalt(I) Hydride Complex
作者:Enrico Bergamaschi、Frédéric Beltran、Christopher J. Teskey
DOI:10.1002/chem.202000410
日期:2020.4.21
the ability to switch the actual function of the catalyst and resulting products. Here we report such an example of multi-dimensional catalysis. Featuring an easily prepared, bench-stable cobalt(I) hydride complex in conjunction with pinacolborane, we can switch the reaction outcome between two widely employed transformations, olefin migration and hydroboration, with visible light as the trigger.
One‐Shot Radical Cross Coupling Between Benzyl Alcohols and Alkenyl Halides Using Ni/Ti/Mn System
作者:Takuya Suga、Yuuki Takahashi、Yutaka Ukaji
DOI:10.1002/adsc.202000945
日期:2020.12.22
A “one‐shot” cross coupling between benzyl alcohols and alkenylhalides has been established. A combination of low‐valent Ti‐mediated C−OH homolysis and the prominent chemistry of Ni‐based radical catalysis afforded the desired cross‐coupled product with good efficiency. The reaction proceeded regardless of the electronic property of benzyl alcohols, and Ar−B bond remained intact throughout the reaction