Fig. 4: Substrate scope for the tandem annulation reactions.

Unless otherwise specified, all the reactions were carried out using racemic ketimine ester 1 (0.15 mmol), hydroquinone 2 (0.225 mmol), Cu(MeCN)4BF4 (10 mol%), (S,Sp)-L4 (12 mol%), KOAc (0.3 mmol), nBu4NClO4 (0.07 M), and THF (4 mL) at −10 °C under constant-current conditions in an undivided cell. a(R,Rp)-L4 was used.