Dynamic Kinetic Sensitization of β-Dicarbonyl Compounds-Access to Medium-Sized Rings by De Mayo-Type Ring Expansion

Tiffany O Paulisch, Lukas A Mai, Felix Strieth-Kalthoff, Michael J James, Christian Henkel, Dirk M Guldi, Frank Glorius

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Herein, we present a photocatalyzed two-carbon ring expansion of β-dicarbonyl compounds with unactivated olefins that provides facile access to medium-sized rings. Selective sensitization of the substoichiometric enol tautomer enables reactivity of substrates incompatible with the classical De Mayo reaction conditions. Key to success is the identification of the metal-based sensitizer fac-[Ir(CF3 -pmb)3 ], which can be excited using common near-visible LEDs, and possesses a high triplet excited state energy of 73.3 kcal mol-1 . This exactly falls in the range between the triplet energies of the enol and keto tautomer, thereby enabling a dynamic kinetic sensitization. Demonstrating the applicability of fac-[Ir(CF3 -pmb)3 ] as a photocatalyst in organic synthesis for the first time, we describe a two-step photocycloaddition-ring-opening cascade with β-ketoesters, -diketones, and -ketoamides. The mechanism has been corroborated by time-resolved spectroscopy, as well as further experimental and computational studies.

Original languageEnglish
Article numbere202112695
Number of pages6
JournalAngewandte Chemie International Edition
Issue number5
Publication statusPublished - 26 Jan 2022

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