Synthesis of spiroindolenine derivatives by a tandem radical-oxidation process

In the present work, a novel stereoselective radical cyclization/oxidation/spirocyclization cascade process using a mixture of n-Bu3SnH/ dilauroyl peroxide is described. The proposed mechanism for this later process combines a 6-endo cyclization of an aryl radical onto an enamide double bond, and a consecutive oxidative-ionic spirocyclization at C-3 of an indole nucleus. All processes led to the construction of new spiroindolenine derivatives in a one-step synthesis starting from relatively simple starting materials. The organic peroxide appears to act as the initiator and the oxidant.