CarbaMic acid, N-[(1R)-1-(3-chlorophenyl)-2-hydroxyethyl]-, 1,1-diMethylethyl ester synthesis

Yield:926291-64-7 51%

Reaction Conditions:

Stage #1: tert-butyl carbazatewith sodium hydroxide;tert-butyl hypochloride in propan-1-ol at 15; for 0.166667 h;
Stage #2: 3-Chlorostyrenewith (DHQD)2PHAL;potassium osmate(VI) in propan-1-ol at 0;

Steps:

J

To a stirred solution of t-butyl carbamate (2.0 equivalents) in n-propanol (4 L/mol) in a cold-water bath (~ 15°C) was added IN NaOH (2.05 equivalents), and t-butyl hypochlorite (2.3 equivalents). The mixture was stirred for 10 min and then cooled to 0⁰C. Solutions of (DHQD)₂PHAL (0.02 equivalents) in n-propanol (4 L/mol), styrene (1 equivalent) in n- propanol (8 L/mol), and K₂OsO₄-2H₂O (0.015 equivalents) were added sequentially. The mixture was stirred at 0⁰C until the reaction was complete. The reaction was quenched by the addition of an aqueous Na₂SO₃ solution until any remaining green color was reduced to yellow/brown. The mixture was concentrated under reduced pressure. In a standard workup, the reaction mixture was partitioned between water and CH₂Cl₂. The phases were separated and the aqueous extracted with CH₂Cl₂. The combined organic extracts were dried (Na₂SO₄ or MgSO₄), filtered and concentrated under reduced pressure. The crude material was purified by flash column chromatography on silica gel.; Using general procedure J, 3-chlorostyrene (28.0 g, 200 mmol) was converted to [(R)-l-(3-chloro-phenyl)-2-hydroxy-ethyl]-carbamic acid tert-butyl ester (27.9g, 51% yield, 99% purity by HPLC, 93.7%ee by HPLC). ¹H NMR (CD₃OD) δ 3.63-3.72 (m, 2H), 4.63-4.67 (m, IH), 7.26-7.37 (m, 2H), 7.43 (s, IH).

References:

WO2007/22371,2007,A2 Location in patent:Page/Page column 27; 31