Development of a General Automated Flow Photoredox ¹⁸F-Difluoromethylation of N-Heteroaromatics in an AllinOne Synthesizer

Abstract

We recently reported a new method for the 18F-difluoromethylation of N-heteroaromatics for positron emission tomography (PET) imaging. The method involves the synthesis of a new 18F-difluoromethylating reagent, 2-[18F]((difluoromethyl)sulfonyl)benzo[d]thiazole, and a flow photoredox 18F-difluoromethylation. For preclinical development and human PET studies with new radiotracers, automation of the process is mandatory, mostly to avoid radioprotection issues due to the use of high amounts of radioactivity and to ensure better reliability of the production. Herein we describe the automation of this 18F-difluoromethylation method on a model substrate, acyclovir, on a commercially available AllinOne (AIO) synthesizer from Trasis. The whole process is completed in 95 min and provides radiolabeled acyclovir with a molar activity of 35 GBq/μmol. This automated protocol can be implemented for the 18F-difluoromethylation of a wide range of N-heteroaromatic compounds typically found in medicinal chemistry.