Fig. 2: Scope of allenes.

^aUnless otherwise noted the reactions were carried out with 1 (0.3 mmol), Co(acac)₂ (10 mol%), tpy (5 mol%), L*4 (5 mol%), HBpin (3.5 equiv), MTBE (1.5 mL), 30 ^oC, 39 h, then oxidized by H₂O₂ (30%, 0.6 mL), NaOH (3 M, 0.6 mL) in THF (2 ml); Isolated yields. Ee was determined by HPLC on a chiral stationary phase. ^bWithout oxidation. ^cNaBO₃•4H₂O was used as an oxidant. ^dHBpin (4.5 equiv). ^eThe reaction was conducted at 20 °C. ^fEnantiomeric excess after recrystallization in the parentheses.