Fig. 4: Cobalt-catalyzed asymmetric hydrogenation of various α,β-unsaturated carboxylic acids.
From: Cobalt-catalyzed highly enantioselective hydrogenation of α,β-unsaturated carboxylic acids
aConditions: 1 (0.1 mmol), Co(acac)2 (1 mol%), (S,S)-Ph-BPE (1 mol%) and Zn (10 mol%) in iPrOH (0.6 mL) under 40 atm H2 pressure at room temperature for 24 h. Yield of isolated products, unless noted otherwise. The ee values were determined by HPLC analysis. bUnder 60 atm H2 pressure, 50 °C. cUnder 80 atm H2 pressure, 50 °C. dWith 5 mol% of Cat. eWith 5 mol% of CoCl2 and (S,S)-Ph-BPE in MeOH (0.4 mL), 72 h. f3 (0.1 mmol), CoCl2 (5 mol%), (S,S)-Ph-BPE (5 mol%), and Zn (50 mol%) in HFIP (0.4 mL) under 60 atm H2 pressure at 50 °C for 48 h. gIn 0.6 mL solvent (MeOH/HFIP = 2/1), 72 h. hIn 0.4 mL MeOH.
