Paulisch Tiffany O, Mai Lukas A, Strieth-Kalthoff Felix, James Michael J, Henkel Christian, Guldi Dirk M, Glorius Frank
Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149, Münster, Germany.
Department Chemie und Pharmazie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058, Erlangen, Germany.
Angew Chem Int Ed Engl. 2022 Jan 26;61(5):e202112695. doi: 10.1002/anie.202112695. Epub 2021 Dec 23.
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(CF -pmb) ], which can be excited using common near-visible LEDs, and possesses a high triplet excited state energy of 73.3 kcal mol . 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(CF -pmb) ] 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.
在此，我们展示了一种光催化的β-二羰基化合物与未活化烯烃的双碳环扩展反应，该反应可方便地合成中环化合物。亚化学计量的烯醇互变异构体的选择性敏化使得底物能够在与经典德 Mayo 反应条件不相容的情况下发生反应。成功的关键在于鉴定出金属基敏化剂 fac-[Ir(CF -pmb) ]，它可以使用常见的近可见光发光二极管激发，并且具有 73.3 kcal mol 的高三重激发态能量。这恰好落在烯醇和酮互变异构体的三重态能量之间，从而实现动态动力学敏化。首次证明 fac-[Ir(CF -pmb) ]作为光催化剂在有机合成中的适用性，我们描述了一种与β-酮酯、二酮和酮酰胺的两步光环加成-开环级联反应。该机理已通过时间分辨光谱以及进一步的实验和计算研究得到证实。
