Radical‐Type Reactivity and Catalysis by Single‐Electron Transfer to or from Redox‐Active Ligands

Abstract

Controlled ligand-based redox-activity and chemical non-innocence are rapidly gaining importance for selective (catalytic) processes. This Concept aims to provide an overview of the progress regarding ligand-to-substrate single-electron transfer as a relatively new mode of operation to exploit ligand-centered reactivity and catalysis based thereon.

Optimizing Group Transfer Catalysis by Copper Complex with Redox-Active Ligand in an Entatic State

“…Such systems are known as redoxactive ligands. This field of research is morphing into an area of intense development aimed at harnessing the potential of systems with rich redox flexibility (Albold et al, 2019;Blanchard et al, 2012;Broere et al, 2015;Chirik and Wieghardt, 2010;Grü tzmacher, 2008;Kaim, 2011;Luca and Crabtree, 2012;Lyaskovskyy and de Bruin, 2012;Praneeth et al, 2012;van der Vlugt, 2012van der Vlugt, , 2019. Recently, an entatic pair of copper complexes bearing redox-active guanidine ligands was shown to enable fine-tuning between metal-and ligand-based electronic transfers (Schrempp et al, 2017).…”

Merging Regiodivergent Catalysis with Atom‐Economical Radical Arylation

“…[2] Herein, we show the validity of these points in at itanocene-catalyzed [3] regiodivergent radical arylation that allows access to enantiomerically pure tetrahydroquinolines or indolines from ac ommon starting material through choice of the appropriate titanocene catalyst. The regioselectivity of epoxideo pening that results in the high selectivity of heterocycle formation is controlled by two factors,t he absolute configuration of the enantiopure ligands of the (C 5 H 4 R) 2 TiX 2 catalyst and the inorganic ligand X( X = Cl, OTs).…”

“…[2] Herein, we show the validity of these points in at itanocene-catalyzed [3] regiodivergent radical arylation that allows access to enantiomerically pure tetrahydroquinolines or indolines from ac ommon starting material through choice of the appropriate titanocene catalyst. Theuse of earth-abundant 3d transition metals [1] that shuttle between neighboring oxidation states is particularly appealing.…”

“…Theuse of earth-abundant 3d transition metals [1] that shuttle between neighboring oxidation states is particularly appealing. [2] Herein, we show the validity of these points in at itanocene-catalyzed [3] regiodivergent radical arylation that allows access to enantiomerically pure tetrahydroquinolines or indolines from ac ommon starting material through choice of the appropriate titanocene catalyst. In regiodivergent reactions,o ne constitutional isomer of ap roduct is formed from an enantiomerically pure substrate by the action of one enantiomer of acatalyst and the other isomer by the action of the other enantiomer of the catalyst.…”

“…Abstract: At itanocene-catalyzed regiodivergent radical arylation is described that allows access to either enantiomerically pure tetrahydroquinolines or indolines from ac ommon starting material. The regioselectivity of epoxideo pening that results in the high selectivity of heterocycle formation is controlled by two factors,t he absolute configuration of the enantiopure ligands of the (C 5 H 4 R) 2 TiX 2 catalyst and the inorganic ligand X( X = Cl, OTs). The overall reaction is atom-economical and constitutes ar adical Friedel-Crafts alkylation.…”