Ion-Pairing Catalysis in Stereoselective, Light-Induced Transformations

Abstract

With the rapid development of photoredox catalysis, numerous concepts for asymmetric induction were successfully and broadly adapted from polar two-electron transformations to radical chemistry. While this applies to organocatalysis or transition metal chemistry, asymmetric ion-pairing catalysis remains a niche application within light-driven reactions today. This perspective gives an overview of recent examples, strategies, and their application in stereoselective transformations at the interface of ion-pairing and photo(redox) catalysis.

Sequence-selective three-component reactions of alkyltrifluoroborates with α,β-unsaturated carbonyl compounds and vinylphosphonium salts

“…A three-component product was neither obtained with even more electron-deficient disulfonyl alkene 36 . Overall, the observed chemoselectivity of the second addition reaction in preference to the vinylphosphonium ion may be due to electrostatic interactions caused by the positive charge of vinylphosphonium cations, 20 but the effect of the highly electron-withdrawing character of the phosphonio group may not be ruled out.…”

Asymmetric Ion-Pairing in Stereoselective Vinyl Polymerization

“…This has broadened the monomer scopes of these methods through catalyst–ligand design, thus providing access to stereoenriched polymers made from simple precursors that demonstrate attractive properties. The fledgling transition from monomer to catalyst design in controlling polymer stereochemistry parallels the advancements from substrate control with directing groups toward purely catalyst control in the fields of small molecule AIP catalysis, stereoselective photoredox chemistry, and C–H functionalization. − ,− …”

Blue Light Irradiated Metal-, Oxidant-, and Base-Free Cross-Dehydrogenative Coupling of C(sp2)–H and N–H Bonds: Amination of Naphthoquinones with Amines

“…Consequently, an environmentally benign, green, and mild approach is highly desirable for C–N bond construction, which can afford densely substituted C2-aminated naphthoquinones and quinones. In recent decades, visible-light-driven photocatalyzed strategies have been developed, serving as a mild and powerful tool for carbon–carbon, − carbon–heteroatom, − and particularly C–N coupling reactions. − In 2016, MacMillan and co-workers reported photocatalyzed aryl amination using ligand-free Ni salt. The visible-light-mediated C 2 -amination of thiophenes with engineered amine substrates by using DDQ as an organo-photocatalyst has been achieved recently by Lei and co-workers .…”