Phosphorus oxychloride → Ethyl 4-chloro-2-methyl-5,6,7,8-tetrahydro[1]benzothieno[2,3-b]pyridine-3-carboxylate

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Reaction Conditions

Reaction Steps

The ethyl(4-hydroxy-2-methyl-5,6,7,8-tetrahydro[1]benzothieno[2,3-b]pyridin-3-yl)carboxylate (2.45 g; 8.41 mmol) was suspended in phosphorus oxychloride (15.7 mL; 168.17 mmol) and the mixture was heated at 100° C. for 40 min. After cooling, the excess of phosphorus oxychloride was removed under reduced pressure, the residue was diluted in ethyl acetate and washed with a saturated solution of sodium hydrogencarbonate, brine and water. The organic layer was dried over sodium sulphate and concentrated under reduced pressure. Purification by flash-chromatography on silica gel using a gradient of ethyl acetate (0-40%) in dichloromethane furnished 1.79 g (68%) of the title compound as a dark oil.

Provenance & Evidence