Trifluoroacetic anhydride → (4-mercaptophenyl) 3 (4-pyridyl) 6,7dihydro[5H]-pyrrolo[1,2-a]imidazole

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Reaction Steps

To 5 q (15.5 mmole) of 2-(4-methylsulfinylphenyl)3 (4-pyridyl)-6,7-dihydro [5H]-pyrrolo[1,2-a]-imidazole prepared as in Example 4 dissolved in 100 ml methylene chloride and cooled to 0° was added 9.7 q (46.4 mmole, 6.5 ml) of trifluoroacetic anhydride in 25 ml of methylene chloride. The mixture was heated to reflux for 1 hour. The reaction mixture was stripped on the rotovap, then treated with water, and extracted with methylene chloride. The extract was washed with 3N NaHCO3 and saturated NaCl and treated with Na2SO4, then stripped to leave 5.1 g of crude product. This material was dissolved in anhydrous methanol (50 ml) and treated with a 25% solution of NaOCH3 /MeOH (5 ml, 23 mmole). This mixture was stirred at room temperature for 3 hours, then poured onto ice water and neutralized with 3N NaHCO3. After removing most of the methanol on the rotovap, the residue was partitioned between methylene chloride and water. The organic layer was washed with water and saturated NaCl, treated with Na2SO4 and stripped. The residue was flash chromatographed on a silica gel column using a gradient of 1 to 5% MeOH in methylene chloride to give 3.1 g (10.5 mmole) of the titled compound.

Provenance & Evidence