Oxidative Dimerization of 2-Oxindoles Promoted by KOtBu-l2: Total Synthesis of (±)-Folicanthine

A transition-metal-free oxidative coupling of 2-oxindoles has been demonstrated in the presence of 1.2 equiv each of potassium tert-butoxide and iodine. The method yields a diverse range of structurally different homo- and heterodimerized 2-oxindoles bearing vicinal all-carbon quaternary centers of great synthetic importance. A radical-driven pathway has been tentatively proposed.