Water → tert-butyl (2S)-2-methyl-8-(1-methylethyl)-2,3-dihydrothieno[2,3-f][1,4]oxazepine-4(5H)-carboxylate

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Reaction Steps

A mixed solution of tert-butyl (2S)-8-bromo-2-methyl-2,3-dihydrothieno[2,3-f][1,4]oxazepine-4(5H)-carboxylate (1.15 g) obtained in Example 12, steps 1-4, isopropenylboronic acid pinacol ester (0.807 mL), dichlorobis(triphenylphosphine)palladium (116 mg) and potassium carbonate (1.37 g) in DME-water (1:1, 30 mL) was stirred at 85° C. for 2 hr under a nitrogen stream. The reaction solution was cooled to room temperature, water was added, and the mixture was extracted with ethyl acetate. The extract was washed with water and saturated brine, and dried over magnesium sulfate, and the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (solvent gradient; 5→12% ethyl acetate/hexane) to give a colorless oil. To a solution of the obtained oil in THF-MeOH (2:1, 30 mL) was added 10% palladium on carbon (100 mg), and the mixture was stirred for 1 hr under a hydrogen atmosphere. The reaction solution was filtered, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (solvent gradient; 0→10% ethyl acetate/hexane) to give the title compound (926 mg, 90%) as a colorless oil.

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