Discovery of a Covalent Triazine Framework Photocatalyst for Visible-Light-Driven Chemical Synthesis using High-Throughput Screening

Abstract

Photoredox catalysis is an important development in organic synthesis, offering distinct reaction pathways under mild conditions. However, to date, most photocatalysts available to synthetic chemists are homogeneous metal complexes or organic dyes, which raise issues of cost, recyclability, and waste production. Here we report the discovery of a covalent triazine framework photocatalyst (CTF-2) for decarboxylative conjugate addition of a range of carboxylic acids under visible-light irradiation. The decarboxylation reaction can be coupled with a variety of other reactions, including metallaphotoredox arylation, alkylation, fluorination, and dehydrogenative aniline synthesis. CTF-2 can be prepared on a large scale and recycled without loss of catalytic efficiency for at least four cycles. To demonstrate application in pharmaceutical drug synthesis, we synthesized (±)-rolipram in five steps from isovanillin using a CTF-2-catalyzed decarboxylative conjugate addition as the key step.