[CH3:1][C:2](=[CH2:4])[CH3:3].[Br:5][CH2:6][C:7]1[CH:16]=[C:15]2[C:10]([CH:11]=[CH:12][CH:13]=[C:14]2[C:17]([OH:19])=[O:18])=[CH:9][CH:8]=1.S(=O)(=O)(O)O>ClCCl>[C:2]([O:19][C:17]([C:14]1[C:15]2[C:10](=[CH:9][CH:8]=[C:7]([CH2:6][Br:5])[CH:16]=2)[CH:11]=[CH:12][CH:13]=1)=[O:18])([CH3:3])([CH3:1])[CH3:4]Isobutylene was passed through a suspension of 7-bromomethylnaphthalene-1-carboxylic acid (10.4 g, 39.2 mmol) in dichloromethane (150 mL) in the presence of concentrated sulfuric acid (1 mL) for 3 hours, and then the mixture was stirred overnight. The resulting deep green solution was washed with a saturated solution of sodium hydrogen carbonate, dried (magnesium sulfate) and the solvent was removed under reduced pressure to give crude 7-bromomethylnaphthalene-1-carboxylic acid tert-butyl ester (11.2 g, 88.8%) as a deep green oil. This compound was directly used for the subsequent Michaelis-Becker alkylation without further purification.
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