Triarylamine-based porous coordination polymers performing both hydrogen atom transfer and photoredox catalysis for regioselective α-amino C(sp)-H arylation

• Published in: Chemical science (Cambridge) Vol. 12; no. 24; pp. 8512 - 852
• Main Authors: Li, Hanning, Yang, Yang, Jing, Xu, He, Cheng, Duan, Chunying
• Format: Journal Article
• Language: English
• Published: CAMBRIDGE Royal Soc Chemistry 28.06.2021; Royal Society of Chemistry; The Royal Society of Chemistry
• Subjects: Catalysis; Chemical reactions; Chemistry; Chemistry, Multidisciplinary; Coordination polymers; Coupling (molecular); Cross coupling; Crystallography; Design for recycling; Design optimization; Hydrogen; Ligands; Nucleophiles; Organic chemistry; Photoredox catalysis; Physical Sciences; Polymers; Reagents; Regioselectivity; Science & Technology; Skips; Thermal stability; DESIGN; ACTIVATION; ELECTRON-TRANSFER; METAL-ORGANIC FRAMEWORKS; C-H ARYLATION; REDUCTION; ALKYLATION; LIGAND; EFFICIENT
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/d1sc00828e

Direct functionalization of C(sp 3 )-H bonds in a predictable, selective and recyclable manner has become a central challenge in modern organic chemistry. Through incorporating different triarylamine-containing ligands into one coordination polymer, we present herein a heterogeneous approach to the combination of hydrogen atom transfer (HAT) and photoredox catalysis for regioselective C-H arylation of benzylamines. The different molecular sizes and coordination modes of the ligands, tricarboxytriphenylamine (H 3 TCA ) and tris(4-(pyridinyl)phenyl)amine ( NPy 3 ), in one coordination polymer consolidate the triarylamine (Ar 3 N) moiety into a special structural intermediate, which enhances the chemical and thermal stability of the polymers and diminishes structural relaxation during the catalytic process. The inherent redox potentials of Ar 3 N moieties prohibit the in situ formed Ar 3 N&z.rad; + to earn an electron from C(sp 3 )-H nucleophiles, but allow the abstraction of a hydrogen atom from C(sp 3 )-H nucleophiles, enabling the formation of the C(sp 3 )&z.rad; radical and the cross-coupling reaction to proceed at the most electron-rich sites with excellent regioselectivity. The new heterogeneous photoredox HAT approach skips several interactions between transient species during the typical synergistic SET/HAT cycles, demonstrating a promising redox-economical and reagent-economical heterogeneous platform that has not been reported for α-amino C-H arylation to form benzylamine derivatives. Control experiments based on monoligand coordination polymers suggested that the mixed-ligand approach improved the photochemical and photophysical properties, providing important insight into rational design and optimization of recyclable photocatalysts for rapid access to complex bioactive molecules and late-stage functionalized pharmaceuticals. The efficiency of photosensitization and hydrogen atom transfer (HAT) catalysis is balanced in a recyclable heterogeneous manner by the modification of the N-central conformation in Cd- MIX .