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Stereodivergent Synthesis of Tetrahydrofuroindoles through Pd‐Catalyzed Asymmetric Dearomative Formal [3+2] Cycloaddition
Author(s) -
Cheng Qiang,
Zhang Fang,
Cai Yue,
Guo YinLong,
You ShuLi
Publication year - 2018
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201711873
Subject(s) - cycloaddition , diastereomer , chemistry , catalysis , stereoselectivity , palladium , acetonitrile , toluene , combinatorial chemistry , catalytic cycle , solvent , stereochemistry , medicinal chemistry , organic chemistry
A stereodivergent synthesis of tetrahydrofuroindoles through palladium‐catalyzed asymmetric dearomative formal [3+2] cycloaddition of nitroindoles with epoxybutenes was developed. The polarity of the solvent was found to play a key role in the diastereoselectivity. In toluene, good to excellent yields (70–99 %), diastereoselectivity (87/13‐>95/5 d.r.), and enantioselectivity (85/15–94/6 e.r.) were obtained, regardless of the properties of the substituents on nitroindoles. In acetonitrile, tetrahydrofuroindoles of a different diastereoisomer were produced with good to excellent yields (75–98 %) and stereoselectivity (78/22–93/7 d.r., 93/7–99/1 e.r.). Mechanistic studies were conducted to illustrate the origin of the diastereodivergency. The kinetic experiments indicate that the rate‐determining step of this reaction is different in different solvents. ESI‐MS experiments also support the existence of key palladium complex intermediates and the catalytic cycle of the reaction.