Modulating stereoselectivity in allylic C(sp3)-H bond arylations via nickel and photoredox catalysis
Long Huang, Marcin Szewczyk, Rajesh Kancherla, Bholanath Maity, Chen Zhu, Luigi Cavallo, Magnus Rueping
Abstract
Abstract While significant progress has been made in developing selective C-H bond cross-couplings in the field of radical chemistry, the site and stereoselectivity remain a long-standing challenge. Here, we present the successful development of stereodivergent allylic C(sp 3 )-H bond arylations through a systematic investigation of the direction and degree of stereoselectivity in the cross-coupling process. In contrast to the signature photosensitized geometrical isomerization of alkenes, the catalytic reaction demonstrates the feasibility of switching the C-C double bond stereoselectivity by means of ligand control as well as steric and electronic effects. Computational studies explain the stereochemical outcome and indicate that excitation of a Ni-allyl complex from singlet to a triplet state results in a spontaneous change of the allyl group coordination and that the subsequent isomerization can be directed by the choice of the ligand to achieve E / Z selectivity.