Pd-Catalyzed Olefination of Furans and Thiophenes with Allyl Esters
作者:Yuexia Zhang、Zejiang Li、Zhong-Quan Liu
DOI:10.1021/ol203013p
日期:2012.1.6
A direct Pd(II)-catalyzed olefination of furans and thiophenes with allyl esters is demonstrated. Under the typical conditions, the dehydrogenative Heck coupling reactions of heteroarenes with allylic esters proceeded via a β-H elimination rather than a β-OAc elimination to give the corresponding γ-substituted allylic esters.
The catalytic activity of a highly reduced Ni catalyst in the context of a Kumada-Corriu cross coupling has been studied. This nickel complex is characterized by its high electron density, stabilized by simple olefin ligands in combination with two Li ions. Landmark reactivity has been found with this precatalyst which operates at cryogenic temperatures, thus allowing the presence of sensitive functionalities. Structural elucidation of oxidative addition intermediates and their reactivity suggest highly reduced species being operative in the C-C bond forming event.