Rapid Access to 2,2-Disubstituted Indolines via Dearomative Indolic-Claisen Rearrangement: Concise, Enantioselective Total Synthesis of (+)-Hinckdentine A

• Published in: Journal of the American Chemical Society Vol. 145; no. 27; pp. 14831 - 14838
• Main Authors: Baidilov, Daler, Elkin, Pavel K., Athe, Sudhakar, Rawal, Viresh H.
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 12-07-2023
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.3c03611

The construction of 2,2-disubstituted indolines has long presented a synthetic challenge without any general solutions. Herein, we report a robust protocol for the dearomative Meerwein–Eschenmoser–Claisen rearrangement of 3-indolyl alcohols that provides efficient access to 2-substituted and 2,2-disubstituted indolines. These versatile subunits are useful for natural product synthesis and medicinal chemistry. The title [3,3] sigmatropic rearrangement proceeds in generally excellent yield and transfers the C3-indolic alcohol chirality to the C2 position with high fidelity, thus providing a reliable method for the construction of enantioenriched 2,2-disubstituted indolines. The power of this methodology is demonstrated through the concise and strategically unique total synthesis of the marine natural product hinckdentine A, which features a dearomative Claisen rearrangement, a diastereocontrolled hydrogenation of the alkene product, a one-pot amide-to-oxime conversion using Vaska’s complex, and a regioselective late-stage tribromination.