Electroreductive Intermolecular Coupling of Coumarins with Benzophenones: Synthesis of 4‑(2-Hydroxyphenyl)-5,5-diaryl-γ-butyrolactones, 2‑(2,2-Diaryl-2,3-dihydrobenzofuran-3-yl)acetic Acids, and 4‑(Diarylmethyl)coumarins

The electroreductive coupling of coumarins with benzophenones in the presence of TMSCl gave adducts reacted at the 4-position of coumarins as trimethylsilyl ethers. From 3-methylcoumarin, 3,4-cis-adducts were formed stereoselectively. The de-trimethylsilylation of the adducts with 1 M HCl aq or TBAF...

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Bibliographic Details
Published in:Journal of organic chemistry 2016-11, Vol.81 (22), p.11043-11056
Main Authors: Kise, Naoki, Hamada, Yusuke, Sakurai, Toshihiko
Format: Article
Language:English
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Summary:The electroreductive coupling of coumarins with benzophenones in the presence of TMSCl gave adducts reacted at the 4-position of coumarins as trimethylsilyl ethers. From 3-methylcoumarin, 3,4-cis-adducts were formed stereoselectively. The de-trimethylsilylation of the adducts with 1 M HCl aq or TBAF in THF at 25 °C produced 4-(2-hydroxyphenyl)-5,5-diaryl-γ-butyrolactones. The γ-butyrolactones were further transformed to 2-(2,2-diaryl-2,3-dihydrobenzofuran-3-yl)­acetic acids by treatment with 1 M HCl aq at reflux temperature. The de-trimethylsilylation of the adducts with 1 M HCl in MeOH afforded 2-(2,2-diaryl-2,3-dihydrobenzofuran-3-yl)­acetic acid methyl esters. The de-trimethylsiloxylation of the adducts or dehydration of the γ-butyrolactones brought about 4-(diarylmethyl)­coumarins.
ISSN:0022-3263
1520-6904
DOI:10.1021/acs.joc.6b02056