Photoreduction of Anthracenes Catalyzed by peri‐Xanthenoxanthene: a Scalable and Sustainable Birch‐Type Alternative

Abstract

AbstractThe typical Birch reduction transforms arenes into cyclohexa‐1,4‐dienes by using alkali metals, an alcohol as a proton source, and an amine as solvent. Capitalizing on the strong photoreductive properties of peri‐xanthenoxanthene (PXX), herein we report the photocatalyzed “Birch‐type” reduction of acenes by employing visible blue light irradiation at room temperature in the presence of air. Upon excitation at 405 or 460 nm in the presence of a mixture of N,N‐diisopropylethylamine (DIPEA) and trifluoromethanesulfonimide (HNTf2) in DMSO, PXX photocatalyzes the selective reduction of full‐carbon acene derivatives (24–75 %). Immobilization of PXX onto polydimethylsiloxane (PDMS) beads (PXX‐PDMS) allowed the use of the catalyst in heterogeneous batch reactions, giving 9‐phenyl‐9,10‐dihydroanthracene in high yield (68 %). The catalyst could easily be recovered and reused, with no notable drop in performance observed after five reaction cycles. Integration of the PXX‐PDMS beads into a microreactor enabled the reduction of acenes under continuous‐flow conditions, thereby validating the sustainability and scalability of this heterogeneous‐phase approach.