OP(O)(O)=O.[OH2:6].C([O-])([O-])=[O:8].[K+].[K+].[CH3:13][C:14]([C:16]1[CH:21]=[CH:20][CH:19]=[CH:18][CH:17]=1)=[CH2:15]>[Pt].O=[Os](=O)(=O)=O.CC(O)(C)C>[C:16]1([C@:14]([OH:8])([CH3:13])[CH2:15][OH:6])[CH:21]=[CH:20][CH:19]=[CH:18][CH:17]=1
A flow cell reactor filled with a 100 cm2 platinum on titanium anode and a 100 cm2 stainless steel cathode--the two electrode compartment being divided by a Nafion® cation exchange membrane--is used. A solution of 5% H3PO4 is circulated through the cathode compartment, while a solution of anolyte consisting of the followings: H2O (2 liters), t-BuOH (2 liters), K3Fe(CN)6 (0.24 mole, 91 g), K2CO3 (4.8 mole, 662 g), the chiral ligand, PHAL-DHQD (0.012 mole, 9.3 g), OsO4 (0.2M in toluene, 0.0008 mole, 4 mL) and α-methylstyrene (1.6 mole, 189 g) is circulated through the anode compartment. A constant current of 3 A (current density 30 mA/cm2) is applied at 15° C. until almost all the α-methylstyrene is consumed (the reaction is followed by thin layer chromatography on silica gel). The product is isolated as described above (Example 6.1) to provide (R)-2-phenyl-1.2-propanediol in 95% yield and 90% ee.
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