N-alkylation of indole via ring-closing metathesis/isomerization/Mannich cascade under ruthenium/chiral phosphoric acid sequential catalysis

A sequential catalysis by combining the Zhan-1B catalyst with chiral phosphoric acid has been utilized for N-alkylation of indole through a ring-closing metathesis/double bond isomerization/Mannich reaction cascade. Enantioenriched γ-lactams were synthesized in up to 92% yield and 95% ee.