Synthesis of tetrahydroisoquinolines and isochromans via Pictet–Spengler reactions catalyzed by Brønsted acid–surfactant-combined catalyst in aqueous media

Perfluorooctanesulfonic acid (PFOSA), Brønsted acid–surfactant-combined catalyst, efficiently catalyzes the Pictet–Spengler reactions of β-arylethyl carbamate derivatives with aldehydes in water. The present reaction is accelerated by the addition of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). PFOSA in HFIP–water (10 v/v %) is also successfully applied to the oxa-Pictet–Spengler reactions of β-arylethyl alcohol compounds.