Pyridinium hydrobromide → methyl 5-bromo-6-cyclohexyl-4H-thieno[3,2-b]pyrrole-2-carboxylate

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Reaction Steps

To a solution of methyl 6-cyclohexyl-4H-thieno[3,2-b]pyrrole-2-carboxylate obtained in Step 7 in chloroform (90 ml) and tetrahydrofuran (90 ml) was added pyridinium hydrobromide perbromide (21.7 g, 68 mmol) under ice-cooling. The mixture was stirred under ice-cooling for 2 hr and concentrated under reduced pressure at room temperature. Ethyl acetate (300 ml) was added to the residue, and the mixture was washed successively with 1M aqueous sodium hydrogen sulfite solution (100 ml×3), water (100 ml), saturated aqueous sodium hydrogen carbonate solution (100 ml×2) and saturated brine (100 ml), and dried over magnesium sulfate. The mixture was filtered and concentrated under reduced pressure, and the obtained solid was washed with a mixed solvent (100 ml) of n-hexane:ethyl acetate (25:1). The solid was collected by filtration, and dried under reduced pressure to give methyl 5-bromo-6-cyclohexyl-4H-thieno[3,2-b]pyrrole-2-carboxylate (17 g, yield 73%).

Provenance & Evidence