Fig. 6: Optimization of desymmetric B–H bond insertion reaction with ethyl α-diazophenylacetate (4a).

Conditions: a 2-arylpyridine-borane (1a) (0.12 mmol, 1.2 equiv), ethyl α-diazophenylacetate (4a) (0.1 mmol, 1 equiv), Cu(MeCN)4PF6 (5 mol%), ligand (6 mol%), solvent (1 mL) at 0 °C for 20 h. b Isolated yield. c Determined by 1H NMR. d Determined by chiral HPLC.