Water → (2R,3S)-2-(2,3-dichloro-4-cyanophenylamino)-3-hydroxybutanoic acid

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

A 500 mL round bottomed flask was charged with diisopropylamine (11.81 mL, 83.60 mmol) and dry THF (100 mL) then the flask was cooled to −5° C. A 2.5M hexane solution of n-butyllithium (30.87 mL, 77.17 mmol) was then added and the mixture was stirred for 1 h at 0° C. This pre-formed LDA solution was then added via cannula to a −78° C. solution of 2-chloro-4-fluorobenzonitrile (10 g, 64.31 mmol) in THF (100 mL) and the mixture was stirred for 2 h. To this was added a solution of hexachloroethane (16 g, 67.58 mmol) in dry THF (50 mL), and the mixture was allowed to warm to room temperature and stirred for 17 h before being concentrated to furnish a yellow solid (12.15 g) which was used directly in the next step without further purification. K2CO3 (17.8 g, 128.62 mol) was added to a solution of 2,3-dichloro-4-fluorobenzonitrile (12.15 g, 64.31 mol) and (2R,3S)-2-amino-3-hydroxybutanoic acid (11.43 g, 0.096 mol) in DMSO (150 mL) at room temperature. The reaction mixture was heated to 75° C. and stirred for 16.5 h, then was allowed to cool to room temperature whereupon water (150 mL) and ethyl acetate (150 mL) was added to the mixture which was then partitioned. The aqueous phase was then washed with EtOAc (70 mL) and the acidified with citric acid monohydrate (19 g). The aqueous phase was then extracted with EtOAc (180 mL) (×2) and the combined organics were washed with water (80 mL), dried (Na2SO4), filtered and concentrated to furnish the title compound as a brown solid (9 g, 48%). 1H NMR (500 MHz, acetone d6, δ in ppm) 7.61 (d, J=8 Hz, 1H), 6.84 (d, J=8 Hz, 1H), 6.02 (d, J=7 Hz, 1H), 4.60-4.57 (m, 1H), 4.39-4.37 (m, 1H) and 1.38 (d, J=7 Hz, 3H).

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