Polymer-Supported Photosensitizers for Oxidative Organic Transformations in Flow and under Visible Light Irradiation

A 2,1,3-benzothiadiazole (BTZ)-based vinyl cross-linker was synthesized and copolymerized with large excesses of styrene using free radical polymerization to deliver heterogeneous triplet photosensitizers in three distinct physical formats: gels, beads, and monoliths. These photosensitizers were employed for the production of singlet oxygen (O-1(2)) and for the aerobic hydroxylation of arylboronic acids via superoxide radical anion (O-2(center dot-)), whereby the materials demonstrated good chemical and light stability. BTZ-containing beads and monoliths were exploited as photo-sensitizers in a commercial flow reactor, and O-1(2) production conversion rate comparable to the rates achieved when a 420 was also demonstrated using direct sunlight irradiation, with a nm LED module is used as the source of photons.