Fig. 4: Scope of substrates regarding various (hetero)arenes and 1,3-dienes.

Reaction conditions were as follows: in the glovebox, CrCl₂ (10 mol%) and (S, R)-L1 (12 mol%) were added to a mixture of THF (0.3 mL for 1,3-Butadiene 2a and 0.6 mL for the rest substituted dienes 2) and DCE (1.4 mL). The mixture was stirred for 15 min at room temperature and transferred to another vial containing Mes₂Acr-tBu₂BF₄ (PC1, 10 mol%), (hetero)arene 1 (0.4 mmol, 2 equiv.), 2a (0.6 mmol, 3 equiv., 2 M in THF, 0.3 mL) or substituted diene 2 (0.6 mmol, 3 equiv.) and aromatic aldehyde 3ab (0.2 mmol, 1 equiv.). The final reaction mixture was irradiated with 30 W 450 nm blue LEDs with a cooling fan for 17 h outside under N₂. Isolated yields. The ee values were determined by HPLC analysis on a chiral stationary phase.