[CH3:1][C:2]([CH3:18])([CH3:17])[C:3]([NH:5][C:6]1[CH:15]=[CH:14][CH:13]=[C:12]([OH:16])[C:7]=1[C:8]([O:10][CH3:11])=[O:9])=[O:4].[CH2:19](Br)[C:20]#[CH:21].C(=O)([O-])[O-].[K+].[K+]>CC(C)=O>[CH3:1][C:2]([CH3:18])([CH3:17])[C:3]([NH:5][C:6]1[CH:15]=[CH:14][CH:13]=[C:12]([O:16][CH2:21][C:20]#[CH:19])[C:7]=1[C:8]([O:10][CH3:11])=[O:9])=[O:4]A mixture of methyl 2-(2,2-dimethylpropionylamino)-6-hydroxybenzoate (Intermediate 47, 4.57 g), propargyl bromide (80% solution in toluene, 2.03 mL) and potassium carbonate (3.74 g) in acetone (35 mL) was heated at reflux for 8 hours. After cooling, the mixture was filtered and the filtrate was concentrated in vacuo. The residue was purified by chromatography on silica, eluting with a mixture of ethyl acetate and cyclohexane, with a gradient of 5-20% to give methyl 2-(2,2-dimethylpropionylamino)-6-(prop-2-ynyloxy)benzoate (4.74 g) as an oil which crystallised on standing to give a white solid.
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