Cu(I)-Catalyzed C-H Alkenylation of Tertiary C(sp 3 )-H Bonds of 3-Aryl Benzofuran-2( 3H )-ones to Give Z - and E -Styrene Containing Quaternary Carbon Centers with 99/1 Regioselectivity.

The synthesis of isomerically pure olefins containing all-carbon quaternary centers is a challenging issue. Herein, we developed an efficient protocol for the synthesis of ( Z )-olefins (27 examples, yield up to 97%, Z / E up to 99/1) and ( E )-olefins (16 examples, yield up to 94%, E / Z up to 99/1) containing all-carbon quaternary centers. This protocol is adopted for the copper-catalyzed regioselective C-H alkenylation of the tertiary C(sp 3 )-H bond of 3-aryl benzofuran-2( 3H )-ones with alkyne and alkenes. A diverse range of functional groups in the substrates is well-tolerated, such as F, Cl, Br, Me, OMe, ester, CF 3 , etc. A gram scale experiment was performed in good yield, and the radical mechanisms are also proposed based on the control experiments.