Cross-Coupling of Alkenes with Styrenes. To validate the feasibility of our hypothesis, we initially conducted the cross-coupling of β-methylstyrene (A1, 2:1 of Z/E mixture) with styrene (B1). The representative results were collected in Table . When the reaction was carried out with A1 (1.0 mmol), B1 (0.10 mmol) and Sc-3/[Ph3C][B(C6F5)4] (1:1, 10 mol%) in 0.5 mL toluene at 100 °C for 12 h, the corresponding Csp 3 -H alkylation D1 was afforded in 95% yield with 5.6:1 E/Z ratio along with a little amount of dimerization product C1 (Table , entry 1). The configuration of alkene A1 has a limited effect on the results (see Scheme 3b for more details). No matter the E/Z ratio of the starting material alkene A1, the remaining A1 was recovered in the same 13:1 E/Z ratio after the reaction in presence of Sc-3 (For more details, see SI, page S19). These results suggested that allylic rare-earth metal species may be formed during the reaction process. The preferential generation of cross-coupling product D1 over homocoupling product C1 was probably attributed to the relatively slow insertion step of sterically bulky alkene A1.