Phosphonium mercaptides

These anionic ring opening polymerizations are usually carried out either in bulk or in solution. A host of catalyst types are active. For synthetic references using specific catalysts, the reader is referred to several excellent sources (4,7,31,32). Representative catalysts include hydroxides, alcoholates, phenolates, silanolates, siloxanolates, mercaptides of the alkali metals, organolithium and potassium compounds, and quaternary ammonium and phosphonium bases and their silanolates and siloxanolates. Some physical characteristics of linear oligomers are given in Table 5 (10). 

Acyl and aroyl disulfides react by a somewhat different route. Both acetyl disulfide (225) and benzoyl disulfide (125) react exothermically with triethyl phosphite at room temperature to produce 0,0,0-triethyl phosphorothioate and the acyl or aroyl sulfide. This result suggests that the acyl-sulfur linkage in the phosphonium intermediate is more susceptible to cleavage by mercaptide ion than is the alkyl-oxygen bond. 

---