Triphenylphosphine → (E)-3-Methylbut-1-ene-1-sulfonyl chloride

To a solution of triphenylphosphine (1.055 g, 4.02 mmol) in dichloromethane (50 ml) under a nitrogen atmosphere was added at 0° C. sulfuryl dichloride (0.359 ml, 4.42 mmol). The mixture was stirred at 0° C. for 15 minutes after which a solution of tetrabutylammonium (E)-3-methylbut-1-ene-1-sulfonate (1.25 g of Step C) in dichloromethane (10 ml) was added dropwise. The reaction mixture was stirred at room temperature for 5 h after which the mixture was concentrated under reduced pressure. The residue was taken up in diethylether and filtered over a glass filter to remove triphenylphosphinoxide. The filtrate was concentrated under reduced pressure to yield 102 mg of a brown oil which was used directly in the next step.