Ring-Closing Metathesis/Isomerization/Pictet–Spengler Cascade via Ruthenium/Chiral Phosphoric Acid Sequential Catalysis

Chiral phosphoric acid worked together with Hoveyda-Grubbs II catalyst enabling highly efficient synthesis of enantioenriched tetrahydro-β-carbolines (up to 98% yield, 99% ee) through a ring-closing metathesis/isomerization/Pictet-Spengler cascade reaction via sequential catalysis.