Synthesis of Cyclobutane-Fused Angular Tetracyclic Spiroindolines via Visible-Light-Promoted Intramolecular Dearomatization of Indole Derivatives

• Published in: Journal of the American Chemical Society Vol. 141; no. 6; pp. 2636 - 2644
• Main Authors: Zhu, Min, Zheng, Chao, Zhang, Xiao, You, Shu-Li
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 13.02.2019; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Multidisciplinary; cycloaddition reactions; diastereoselectivity; energy transfer; moieties; Physical Sciences; Science & Technology; N-BENZOYLINDOLE; CATALYSIS; ALKYLATION; PRENYLATION; CONSTRUCTION; PHOTOCATALYSIS; 2+2 PHOTOCYCLOADDITION REACTIONS; CYCLIZATION; PYRROLOINDOLINES; PHOTOCHEMICAL CYCLOADDITION REACTIONS
• ISSN: 0002-7863; 1520-5126; 1520-5126
• DOI: 10.1021/jacs.8b12965

An intramolecular dearomatization of indole derivatives based on visible-light-promoted [2+2] cycloaddition was achieved via energy transfer mechanism. The highly strained cyclobutane-fused angular tetracyclic spiroindolines, which were typically unattainable under thermal conditions, could be directly accessed in high yields (up to 99%) with excellent diastereoselectivity (>20:1 dr) under mild conditions. The method was also compatible with diverse functional groups and amenable to flexible transformations. In addition, DFT calculations provided guidance on the rational design of substrates and deep understanding of the reaction pathways. This process constituted a rare example of indole functionalization by exploiting visible-light-induced reactivity at the excited states.