Diisopropylethylamine → 1-(Isopropylsulfonyl)piperazine

A solution of 1-BOC-piperazine (0.617 mmol) and diisopropylethylamine (0.679 mmol) in 0.5 mL of methylene chloride was added to a 4 mL vial. Propane-2-sulfonyl chloride (0.679 mmol) was added to the vial, and the reaction mixture was shaken overnight at room temperature. When the reaction was complete, it was diluted with 1.5 mL of methylene chloride and extracted with 1 mL of 1N solution of hydrogen chloride followed by 1 mL of 10% potassium carbonate solution. The organic layer was concentrated in vacuo. The residue was dissolved in 0.5 mL of tetrahydrofuran and 4M solution of hydrogen chloride in dioxane (0.5 mL). The solution was shaken overnight at room temperature then concentrated in vacuo to give 1-(propane-2-sulfonyl)-piperazine.