Green-Light Photocatalysis: Borylated Benzo[<i>c</i>][1,2,5]thiadiazole (BTZ) Enables Phosphorylation of Quinoline Derivatives

A library of 10 novel organophotocatalysts (<b>ORG-PRCs</b>) has been prepared by the one-pot, two-step <i>ortho</i>-borylation of 4,7-diarylbenzo[<i>c</i>][1,2,5]thiadiazoles (<b>BTZs</b>). The borylation reaction was accompanied by a substantial bathochromic shift in both the absorption and emission spectra (up to 142 nm), allowing these photocatalysts to operate using low-energy green light instead of the high-energy near-UV light that <b>BTZ</b> photocatalysts typically require. The library of photocatalysts was tested using the phosphorylation of quinoline compounds under both batch and recycle flow conditions, achieving up to 40 and 73% conversion, respectively, in 4 h. The versatility of the recycle flow system was further tested by developing a sequential two-step phosphorylation followed by a Minisci coupling procedure using a dual photocatalyst system. This allowed automated production of the target antibacterial phosphorylated quinoline derivative with a total conversion of 64% from abundant, inexpensive, and late-stage modifiable starting materials in a streamlined process.