Ene reactions of 2-borylated α-methylstyrenes a practical route to 4-methylenechromanes and derivatives

Chaima Boureghda (1) , Aurélie Macé (1) , Fabienne Berrée (1) , Thierry Roisnel (1) , Abdelmadjid Debache (2) , Bertrand Carboni (1)

1 ISCR - Institut des Sciences Chimiques de Rennes
2 UMC - Université Frères Mentouri – Constantine 1 = Constantine 1 – Frères Mentouri University

4-Methylenechromanes were prepared via a three-step process from 2-borylated -methylstyrenes. This sequence is based on a key glyoxylate-ene reaction catalyzed by scandium(III) triflate. The resulting -hydroxy boronates, which cyclise to seven-membered homologues of benzoxaborole on silica gel, were cleanly oxidized with sodium perborate, 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.

Domaines: Chimie

Chaima Boureghda, Aurélie Macé, Fabienne Berrée, Thierry Roisnel, Abdelmadjid Debache, et al.. Ene reactions of 2-borylated α-methylstyrenes a practical route to 4-methylenechromanes and derivatives. Organic & Biomolecular Chemistry, 2019, 17 (23), pp.5789-5800. ⟨10.1039/c9ob00963a⟩. ⟨hal-02150447⟩