Synthesis of 1 H -Isochromenes and 1,2-Dihydroisoquinolines by Indium(III)-Catalyzed Cycloisomerization of ortho -(Alkynyl)benzyl Derivatives.

1 H -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 1 H -isochromenes and 1,2-dihydroisoquinolines through a domino cycloisomerization/reduction approach. [ABSTRACT FROM AUTHOR]