Boureghda C, Macé A, Berrée F, Roisnel T, Debache A, Carboni B. Ene reactions of 2-borylated α-methylstyrenes: a practical route to 4-methylenechromanes and derivatives.
Org Biomol Chem 2019;
17:5789-5800. [PMID:
31135020 DOI:
10.1039/c9ob00963a]
[Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
4-Methylenechromanes were prepared via a three-step process from 2-borylated α-methylstyrenes. This sequence is based on a key glyoxylate-ene reaction catalyzed by scandium(iii) triflate. The resulting γ-hydroxy boronates, which cyclise to seven-membered homologues of benzoxaborole on silica gel, were cleanly oxidized with sodium perborate, and then cyclised under Mitsunobu conditions. Additionally, several further functional transformations of 4-methylenechromanes or their precursors were carried out to illustrate the synthetic potential of these intermediates.
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