 Use of a sulfoxonium allows more <unk> preparation of the reagent using weaker bases as compared to sulfonium ylides . ( The difference being that a sulfoxonium contains a <unk> bonded oxygen whereas the sulfonium does not . ) The former react slower due to their increased stability . In addition , the <unk> by @-@ products of sulfoxonium reagents are greatly preferred to the significantly more toxic , volatile , and <unk> <unk> by @-@ products from sulfonium reagents . 
