O-(1,1-Dimethylethyl) S-(4,6-dimethyl-2-pyrimidinyl) carbonothioate → 2-Tert-butoxycarbonyl-1,2,3,4-tetrahydrobenzo[b]thieno[2,3-c]pyridine-carboxylic acid ethyl ester

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Reaction Steps

In 20 ml of desiccated chloroform were dissolved 6 g of 1,2,3,4-tetrahydro-benzo[b]thieno[2,3-c]pyridinecarboxylic acid ethyl ester synthesized in Example 1 and 6.63 g of 2-(tertiary-butoxycarbonylthio)-4,6-dimethylpyrimidine, and the solution was refluxed for 30 minutes. After distilling off chloroform under reduced pressure, the residue was dissolved in 300 ml of ethyl acetate and the solution was washed thrice with 50 ml of an aqueous 5% sodium hydrogencarbonate, twice with an aqueous 5% citric acid solution, and then twice with a saturated aqueous sodium chloride solution and thereafter dried with sodium sulfate. Ethyl acetate was distilled off under reduced pressure and the residue was recrystallized from a mixture of chloroform and petroleum ether to provide 6.18 g (yield of 76%) of 2 -tert-butoxycarbonyl-1,2,3,4-tetrahydro-benzo[b]thieno[2,3-c]pyridine-carboxylic acid ethyl ester.

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