Visible Light-Driven Flexible Synthesis of α-Alkylated Glycine Derivatives Catalyzed by Reusable Covalent Organic Frameworks

Abstract

Herein, we report a heterogeneous visible lightdriven preparation of α-alkylated glycine derivatives. This approach employed a β-ketoenamine-linked covalent organic framework (2D-COF-4) as the heterogeneous photocatalyst and N-hydroxy phthalimide (NHPI) esters as the alkyl radical sources. Numerous glycine derivatives, including dipeptides, were precisely and efficiently alkylated under visible light-driven reaction conditions. Based on the excellent photoactivity and organic reaction compatibility of 2D-COF-4, this alkylation could proceed flexibly in a green solvent (ethanol) without any other additives. The photocatalyst and phthalimide were fruitfully recycled with a simple workup procedure, revealing a high ecoscale value and low environmental factor (E-factor).

Visible‐Light‐Induced Stereoselective C(sp3)−C(sp3)−H Glycosylation for the Synthesis of C‐Glycoamino Acid Derivatives

“…Based on the above experiments and previous reports, [34] a plausible mechanism is depicted in Scheme 5. Under visible light irradiation, the photocatalyst Ph-PTZ was turned into its excited form Ph-PTZ*, which next underwent a single electron transfer (SET) process with glycosyl NHP ester 2 a to generate Ph-PTZ * + and a radical anion I.…”

All-in-one Rh(iii)-covalent organic framework for sustainable and regioselective C(sp2)–H bond functionalization

“…To address the issues mentioned above, continuing our efforts on COF application in green organic synthesis, 16 herein, we report the synthesis of an Rh( iii )-covalent organic framework (RhCOF-SYNU-1) and its catalytic application in regioselective C(sp 2 )–H bond functionalization reactions (Scheme 1b and c). Through the organic units' solvothermal assembly, chemical modification, and post-metalation with the Rh( iii ) donor, RhCOF-SYNU-1 acquired a high BET surface area, excellent stability, homo Rh( iii ) site dispersion, and facile visible-light harvesting ability.…”

Flexible vs. rigid covalent organic frameworks: catalytic performance in the Knoevenagel reaction

“…Application research has shown that previously reported covalent organic frameworks (COFs), composed solely of C, H, O, and N, can undergo effective modulation of their active sites through the incorporation of heteroatoms such as N, O, and P, ultimately enhancing their catalytic performance. 21–24 Based on these findings and the aforementioned assumptions regarding rigid/flexible COFs, the flexible DAPO-TFPC-COF and rigid DAPO-TFPT-COF were synthesized accordingly (Fig. 1).…”