Catalytic cyclometallation of allylbenzenes by EtAlCl2 and Mg as new route to synthesis of dibenzyl butane lignans

The cyclometallation of allylbenzenes (Ar= Ph, 4-MeO-Ph, 3,4-(MeO)2-Ph) with EtAlCl2 (Et2AlCl) and Mg in the presence of Zr and Ti catalysts (Dzhemilev reaction) has been studied. The reaction runs with high diastereoselectivity and provides 2R(S), 3R(S)-dibenzyl butanes with yield of 48-69%.