Site‐Selective (Z)‐α‐Borylalkenyl Copper Systems for Nucleophilic Stereodefined Allylic Coupling

1,1‐Diborylalkenes can be transformed into (Z)‐skipped dienes through Cu(I)‐phosphine catalyzed allylic coupling reactions. The energetically preferred formation of (Z)‐α‐borylalkenyl copper (I) species and the subsequent nucleophilic attack, explains the stereoselective nucleophilic substitution with allyl bromides. The eventual treatment of (Z)‐skipped dienes with NaO( t )Bu promotes cyclization/aromatization patterns via enyne intermediates.