Substituent effects at the origin of a free-radical 1,2-aryl migration and in the related disproportionation reaction of 10-hydro-9-p-X-phenyl-9-phenanthryl radicals
We describe a novel and highly efficient metal-free strategy to construct 9,9-disubstituted fluorenes and phenanthrenes via the TfOH-catalyzed cycloisomerizations of o-alkynylbiaryls. Notably, the significant effects of the electronic properties and steric hindrance of the alkyne terminus on the reaction selectivity have been observed.
Iridium-Catalyzed Formal [4 + 1] Cycloaddition of Biphenylenes with Alkenes Initiated by C–C Bond Cleavage for the Synthesis of 9,9-Disubstituted Fluorenes
作者:Hideaki Takano、Kyalo Stephen Kanyiva、Takanori Shibata
DOI:10.1021/acs.orglett.6b00619
日期:2016.4.15
An Ir-catalyzed intermolecular reaction of biphenylenes as a C4 unit with various alkenes as a C1 unit gave 9,9-disubstituted fluorenes in moderate to high yields. Preliminary mechanistic studies revealed that this formal [4 + 1] cycloaddition probably proceeds via C–C bond cleavage, alkene insertion, β-hydrogen elimination, intramolecular alkene insertion, and then reductive elimination. An example