Phosphorus pentachloride → (4-Pyridylmethyl)sulfonyl chloride triflate

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Reaction Steps

Trifluoromethanesulfonic acid (100 g, 0.67 mol) was rapidly added to a suspension of 4-pyridylmethanesulfonic acid (103 g, 0.6 mol) in phosphorous oxychloride (300 ml). The pyridylmethanesulfonic acid dissolved and reprecipitated as the triflate salt. The resulting suspension was cooled in ice for 30 min, then treated with phosphorous pentachloride (139 g, 0.67 mol) in Portions during 10 minutes. The mixture was allowed to warm to room temperature over 30 min and was then cautiously heated to reflux over a period of 1.5 hrs during which time extensive gas evolution occurred. After refluxing for 1 hr, the excess phosphorous oxychloride was distilled off under vacuum while maintaining the pot temperature below 80° C. The residual solid was dissolved in acetonitrile (200 ml), filtered and crystallized by the gradual addition of ether (400 ml). The product was recovered by filtration and washed with ether to afford a white solid (170 g, 84%).

Provenance & Evidence