Ethyl Acetate → 4-t-Butyl-5-(4-methoxy-2-phenylbenzo[d]oxazol-6-yl)-3,3-dimethyl-2,3-dihydrofuran

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To 1.00 mL (5.82 mmol) of trimethyl orthobenzoate was added 204 mg (0.70 mmol) of 5-(4-amino-3-hydroxy-5-methoxyphenyl)-4-t-butyl-3,3-dimethyl-2,3-dihydrofuran (Compound [61]), and the mixture was refluxed for 1.5 hours at 150° C. To this reaction mixture, 2.0 ml of ethyl acetate, and 0.2 ml of H2O, and 10.1 mg (0.05 mmol) of TsOH H2O was added and the mixture was refluxed for 1 hours at 97° C. The resulting mixture was poured in saturated aqueous solution of sodium hydrogencarbonate and extracted with ethyl acetate. The organic layer was washed with saturated aqueous solution of sodium chloride, dried with magnesium sulfate anhydride, and concentrated. The residue was applied to a silica gel column and the elution was carried out with the mixture of hexane and ethyl acetate (hexane:ethyl acetate=10:1) to obtain 207 mg of 4-t-butyl-5-(4-methoxy-2-phenylbenzo[d]oxazol-6-yl)-3,3-dimethyl-2,3-dihydrofuran (Compound [62]). Yield 78.4%.

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