Sulfuric Acid → (2R)-2-bromo-3-cyclohexylpropanoic acid

Participants

Reaction Conditions

Reaction Steps

A solution of sodium nitrite (0.45 g, 6.5 mmol) in water (1.2 ml) was added dropwise at 0° C. over 4 hours to a stirred mixture of (R)-α-aminocyclohexanepropionic acid (1 g, 5.8 mmol), potassium bromide (2.3 g, 19.2 mmol) and concentrated sulphuric acid (0.66 ml) in water (7 ml). The mixture was stirred for 5 hours at 0° C. then at ambient temperature for 16 hours. The product was extracted into diethyl ether (4×20 ml) then the combined ethereal layers were washed with saturated aqueous sodium chloride solution (2×50 ml), dried (MgSO4) and the solvent removed in vacuo. The residue was purified by chromatography over silica gel eluting with a gradient of methanol:dichloromethane 1:50→1:20. Appropriate fractions were combined and the solvents removed in vacuo to give (R)-α-bromocyclohexanepropionic acid as a pale yellow oil 0.374 g, (27%). TLC (single spot, Rf=0.45, 10% methanol in dichloromethane), HPLC-MS (single main peak with Rt=8.88 mins, 234.1/236.1 [M+H]+, 257.2/259.2 [M+Na]+).

Provenance & Evidence