Cyclopropyldiphenylsulfonium tetrafluoroborate (CAS NO.: ), which is also known as Sulfonium, cyclopropyldiphenyl tetrafluoroborate(1-), could be produced through the following synthetic routes.

A. 3-Chloropropyldiphenylsulfonium tetrafluoroborate (CAS NO.: ). A solution of 93.0 g. (0.500 mole) of diphenyl sulfide and 347 g. (1.70 mole) of 1-chloro-3-iodopropane in 200 ml. of nitromethane in a 1-l., one-necked flask equipped with a magnetic stirring bar and a nitrogen inlet tube is stirred at room temperature under nitrogen. The flask is shielded from light, and 78 g. (0.40 mole) of silver tetrafluoroborate is added in one portion. Initially the temperature rises to 40°, then gradually falls to room temperature. No external cooling is necessary. After 16 hours 200 ml. of dichloromethane is added, the mixture is filtered through a sintered glass funnel fitted with a 35 g. pad of Florisil, and the solid is washed with 100 ml. of dichloromethane. The dichloromethane portions are combined and evaporated at reduced pressure until a solid separates; 1 l. of diethyl ether is added to precipitate the product. The off-white crystals are collected, washed with ether, and dried under reduced pressure at 25°, yielding 122–140 g. (87–99%) of the sulfonium salt, m.p. 103–105°.

B. Cyclopropyldiphenylsulfonium tetrafluoroborate (CAS NO.: ). A suspension of 118.7 g. (0.3386 mole) of 3-chloropropyldiphenylsulfonium tetrafluoroborate in 500 ml. of dry tetrahydrofuran is placed in a 2-l., one-necked flask equipped with a magnetic stirring bar and nitrogen inlet tube under nitrogen before 5-g. portions of 55% sodium hydride–mineral oil dispersion (15.2 g., 0.350 mole) are added in 30-minute intervals. The resulting mixture is stirred at room temperature for 24 hours. An aqueous solution of 25 ml. of 48% fluoroboric acid, 15 g. of sodium tetrafluoroborate, and 400 ml. of water is added to the well-stirred reaction to destroy residual hydride and swamp out chloride ion. After 5 minutes 300 ml. of dichloromethane is added, and the top organic layer is removed from the lower aqueous layer. The dichloromethane solution is then extracted with 100 ml. of water. The combined water layers are extracted with an additional 100 ml. of dichloromethane. The organic phases are combined, dried over anhydrous sodium sulfate, and evaporated at reduced pressure until precipitation occurs. Addition of 1 l. of ether completes the precipitation of the salt. The crystals are collected, washed with ether, recrystallized from hot absolute ethanol (approximately 400 ml.), and dried under reduced pressure, yielding 79.5–88.0 g. (75–83%) of cyclopropyldiphenylsulfonium tetrafluoroborate, m.p. 137–139°.