The reactions of (dimethylamino)phenylsulfoxonium methylide with aldehydes gave unusual cyclopropylaminosulfoxonium salts in good yields when 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU) was used as a base. This ylide reacted with aldehydes to give the corresponding betaines, which resulted in the formation of vinylsulfoxonium salts. The additional ylide reacted with these salts to afford cyclopropylsulfoxonium salts.