Phosphoric Acid → (S)-2-hydroxypropiophenone

Participants

Reaction Steps

A divided glass H-cell as described in Example-6.1 which is equipped with a platinum-on-titanium metal anode (5 cm2) and a nickel foil cathode is charged in the cathode compartment with 50 mL of 8% H3PO4 solution and in the anode compartment with K3Fe(CN)6 (1.71 g, 4.5 mmol), K2CO3 (10.35 g, 75.0 mmol) and t-BuOH (45 mL)/water (50 mL), the chiral ligand, PHAL-DHQ (175 mg. 0.225 mmol), OsO4 (0.196M in toluene, 0.077 mL, 0.015 mmol) and Z-1-chloro-1-phenylpropene (6.9 g, 66.6% purity, 30 mmol). The mixture is electrolyzed at 0.4 V (vs ref. Ag/AgCl) at 15° C. until about 4950 coulombs (85% conversion) of electricity is used. After stirring without electricity for 2 hours, the reaction is worked up as in Example 6.1 using ethyl acetate as the extraction solvent to give (S)-2-hydroxypropiophenone as a yollow liquid (6.8 g, 95.1% ee by HPLC analysis on a Chiralcell OD column). The crude product is purified on slica gel eluting with 5-15% ethyl acetate in hexane to give pure (S)-2-hydroxypropiophenone as a pale yellow solid (3.0 g).

Provenance & Evidence