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Sc(OTf)3-Catalyzed Domino Michael Addition/Hemiketalization of Electron-Rich Phenols and 2-Cinnamoylpyridine 1-Oxides
Ningning Li1, Chengzhuo Wang1, Wenlong Tong1
1Department of Organic Chemistry, College of Chemistry, Beijing University of Chemical Technology, Beijing, China.
Abstract:
Scandium triflate-catalyzed tandem reaction of electron-rich phenols and 2-cinnamoylpyridine 1-oxides is realized. This protocol enables the highly diastereoselective construction of 2,3-dihydrobenzopyrans (chromanes) via a domino Michael addition (Friedel-Crafts alkylation) and hemiketalization process under mild conditions. Using 2-cinnamoylpyridine 1-oxides as Michael acceptors, electron-rich phenols can be extended to methylphenols. The diastereoselectivity is mainly decided by the stability of diastereomeric products, but is impacted by steric and electronic effects. The current study expands the synthetic toolbox for benzopyran derivatives.
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