Anti-Markovnikov hydroallylation reaction of alkenes via scandium-catalyzed allylic C‒H activation

Here, we described a direct anti-Markovnikov hydroallylation reaction of styrene derivatives with 1-aryl-2-alkyl alkenes and α-alkenes by rare-earth metal catalysts. This protocol provided a straightforward and atom-efficient route for the synthesis of valuable chain elongated internal alkenes (65 examples, up to 99% yield, >19:1 E/Z ratio). The reaction proceeded via an allylic Csp3‒H activation pathway initiated by site-selective deprotonation with the assistance of cationic imidazolin-2-iminato scandium alkyl species followed by alkene insertion into the resulting scandium-allyl bond. A catalytic amount of Lewis base additives, such as amine and THF showed significant effects on the reactivity and E/Z selectivity. The reaction mechanism has been elucidated by experimental studies and theoretical calculations.