Ni-Catalyzed Reductive Dicarbofunctionalization of Nonactivated Alkenes: Scope and Mechanistic Insights

Olefins devoid of
directing or activating groups have been dicarbofunctionalized
here with two electrophilic carbon sources under reductive conditions.
Simultaneous formation of one C­(sp3)–C­(sp3) and one C­(sp3)–C­(sp2) bond across
a variety of unbiased π-systems proceeds with exquisite selectivity
by the combination of a Ni catalyst with TDAE as sacrificial reductant.
Control experiments and computational studies revealed the feasibility
of a radical-based mechanism involving, formally, two interconnected
Ni­(I)/Ni­(III) processes and demonstrated the different ability of
Ni­(I) species (Ni­(I)I vs PhNi­(I)) to reduce the C­(sp3)–I
bond. The role of the reductant was also investigated in depth, suggesting
that a one-electron reduction of Ni­(II) species to Ni­(I) is thermodynamically
favored. Further, the preferential activation of alkyl vs aryl halides
by ArNi­(I) complexes as well as the high affinity of ArNi­(II) for
secondary over tertiary C-centered radicals explains the lack of undesired
homo- and direct coupling products (Ar–Ar, Ar–Alk) in
these transformations.