INVESTIGATING THE DIASTEREOSELECTIVITY OF PHOTOREDOX α-ARYLATION OF AMINES

Abstract

This thesis investigates the diastereoselectivity of a novel visible-light photoredox-catalyzed C-H bond activation reaction that introduces aryl groups at the position adjacent to a tertiary amine nitrogen. To examine the diastereoselectivity of the α-arylation of amines reaction, a variety of acyclic amines bearing a chiral center at the β position, two atoms away from nitrogen, were synthesized. The stereochemical outcome of the products of acyclic amine substrates successfully functionalized under the photoredox amine α-arylation conditions were assessed by X-ray crystallography. Under the conditions of fac-Ir(ppy)({3}) photoredox-catalyzed α-arylation with cyanoarenes, 1,2-disubstituted acyclic amines bearing a hydrogen, methyl group, and TBS-protected alcohol bonded to the chiral center β carbon engage in photocoupling with high diastereoselectivity (>20:1) in moderate to high yield. The excellent levels of diastereoselectivity observed in this reaction may be rationalized using a model of asymmetric induction that considers allylic 1,3-strain in deriving the favored energyminimized conformer. In the A({1,3})-minimized molecular conformations, facial discrimination of arene radical anion in approach of the acyclic amine induces the unusually high diastereoselectivity observed in the aminoalcohol case.