I have a sulfonylation that I am trying to optimize. The reactants are an aniline with an aryl sulfonyl chloride, using a pyridyl base. My substrate exhibits poor solubility in most solvents, and I have been trying polar solvents like NMP and DMAc. They work well enough, but the sulfonyl chloride degrades with those solvents. Further, bis-sulfonylation is problematic, since I have to use a slight excess of the sulfonyl chloride to achieve good conversion.

I would like to screen sulfolane, since it should not react with the sulfonyl chloride, but I have been starting the reactions either at room temperature or 0 C, at which point sulfolane is a solid. I have read that small amounts of water depresses the melting point, but I would like to operate under anhydrous conditions.

Does anyone have experience using additives other than water to liquify sulfolane?