Fig. 3: Substrate scope of catalytic asymmetric formal (4 + 5) cycloaddition.

Reaction conditions: 1 (0.1 mmol), 2 (0.2 mmol), (R)−4j (30 mol%), DCE (1 mL), 3 Å MS (100 mg), and 30 °C for 5 h. Isolated yields were provided, and ee values were determined using HPLC. a35 mol% (R)−4j.