This article is dedicated to Prof. Cristina Nevado in celebration of the Dr. Margaret Faul Women in Chemistry Award.
Abstract
1H-Isochromenes and 1,2-dihydroisoquinolines are synthesized by regioselective indium(III)-catalyzed intramolecular hydrofunctionalization of o-(alkynyl)benzyl derivatives. The reaction with o-(alkynyl)benzyl alcohols and amines proceeds using indium triiodide (5–10 mol%) in toluene at 80–100 °C via regioselective 6-endo-dig intramolecular alkyne hydroalkoxylation or hydroamination in good yields. Alternatively, the cycloisomerization reaction of o-(alkynyl)benzaldehydes and imine derivatives using InI3 (5 mol%) and the Hantzsch ester (120 mol%) takes place, under milder reaction conditions, to give a variety of functionalized 1H-isochromenes and 1,2-dihydroisoquinolines through a domino cycloisomerization/reduction approach.
Key words
homogeneous catalysis - indium catalysis - cycloisomerization - alkynes - π-acid catalysis