Nickel-catalyzed dimerization of pyrrolidinoindoline scaffolds: systematic access to chimonanthines, folicanthines and (+)-WIN 64821.

While metal-promoted activation of tertiary alkyl halides often causes elimination and hydrodehalogenation, we have developed a nickel-catalyzed reductive dimerization that allows the generation of a potently reactive tertiary radical equivalent to form a very congested C(sp(3))-C(sp(3)) bond even below room temperature. The catalytic protocol is applicable to the dimerization of several pyrrolidinoindoline scaffolds through an appropriate choice of catalyst to accommodate different substrate reactivities with functional group compatibilities. The efficiency of the nickel-catalyzed protocol was successfully demonstrated through a systematic total synthesis of chimonanthines, folicanthines and (+)-WIN 64821.