Acetic Acid → Racemic tert-butyl 2-(3,4-dichlorophenyl)-6-methoxy-4-oxochroman-3-carboxylate

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A solution of tert-butyl 3-(2-hydroxy-5-methoxyphenyl)-3-oxopropanoate (500 mg, 1.88 mmol) in isopropanol (5.0 mL) was treated with 3,4-dichlorobenzaldehyde (329 mg, 1.88 mmol), piperidine (20 μL, 188 μmol) and acetic acid (10 μL, 188 μmol). The reaction mixture was heated at reflux overnight, and then treated with water (1.0 mL). The resulting mixture was cooled to rt and then concentrated under vacuum to yield a residue. The residue was purified by column chromatography (silica gel, 2-25% ethyl acetate-hexane) to provide racemic tert-butyl 2-(3,4-dichlorophenyl)-6-methoxy-4-oxochroman-3-carboxylate as a yellow oil (380 mg, 48%). This material was used without further purification in Step 3 below.

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