[Cl:1][C:2]1[CH:3]=[C:4]([CH:8]=[CH:9][C:10]=1[C:11]([O:13][CH3:14])=[O:12])[C:5]([OH:7])=[O:6].C1N=CN(C(N2C=NC=C2)=O)C=1.[CH3:27][C:28](O)([CH3:30])[CH3:29].C1CCN2C(=NCCC2)CC1>CN(C=O)C>[CH3:14][O:13][C:11](=[O:12])[C:10]1[CH:9]=[CH:8][C:4]([C:5]([O:7][C:28]([CH3:30])([CH3:29])[CH3:27])=[O:6])=[CH:3][C:2]=1[Cl:1]3-Chloro-4-methoxycarbonylbenzoic acid (0.24 g) was dissolved in DMF (2.5 mL) under N2 then CDI (0.36 g) was added and the resulting mixture was stirred at 40° C. for 2 h. t-BuOH (0.54 mL) and DBU (0.33 mL) were added and the resulting mixture was stirred at 40° C. for 2 days. The mixture was evaporated and the residue was taken up with AcOEt, washed with 1N HCl and sat. NaHCO3, dried (MgSO4), filtered and evaporated. The residue was purified by column chromatography (silica gel; eluent: toluene) to give 2-chloro-4-(tert-butoxycarbonyl)benzoic acid methyl ester (216 mg).
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