Continuous flow photochemistry as an enabling synthetic technology: synthesis of substituted-6(5H)-phenanthridinones for use as poly(ADP-ribose) polymerase inhibitors

• Y. Fang ^a
• G. K. Tranmer ^*a,b

• ^* Corresponding authors ^a College of Pharmacy, Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada
• ^b Department of Chemistry, Faculty of Science, University of Manitoba, Winnipeg, Canada

Methods utilizing continuous flow photochemistry, an enabling synthetic technology, have been developed for the generation of phenanthridinones via an intramolecular photochemical cyclization of 2-chlorobenzamides for the purposes of generating poly(ADP-ribose) polymerase inhibitors. Herein we report 16 examples of a single-step flow photocyclization which produces substituted phenanthridinones in yields up to 99%, while a two-step method leads directly to phenanthridinones from 2-chlorobenzoyl chlorides and anilines via a novel continuous flow amidation/photocyclization protocol. Overall, the flow photocyclization reactions typically progress in good to excellent yields, and in a superior fashion to analogous batch methods, greatly enabling the drug discovery process.

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