Photoredox-Catalyzed Dehydrogenative Csp3–Csp2 Cross-Coupling of Alkylarenes to Aldehydes in Flow

• Oliver M. Griffiths^a
• Henrique A. Esteves^a
• Yiding Chen^a
• Karin Sowa^a,b
• Oliver S. May^a
• Peter Morse^c
• David C. Blakemore^c
• Steven V. Ley*^a

• ^aYusuf Hamied Department of Chemistry, University of Cambridge, CB2 1EW Cambridge, U.K.
• ^bDepartment of Chemistry, University of Münster, 48149 Münster, Germany
• ^cMedicine Design, Pfizer, Inc., Groton, Connecticut 06340, United States

Executing photoredox reactions in flow offers solutions to frequently encountered issues regarding reproducibility, reaction time, and scale-up. Here, we report the transfer of a photoredox-catalyzed benzylic coupling of alkylarenes to aldehydes to a flow chemistry setting leading to improvements in terms of higher concentration, shorter residence times, better yields, ease of catalyst preparation, and enhanced substrate scope. Its applicability has been demonstrated by a multi-gram-scale reaction using high-power light-emitting diodes (LEDs), late-stage functionalization of selected active pharmaceutical ingredients (APIs), and also a photocatalyst recycling method.

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