A Reusable Ring-Enlarging Catalyst

Significance

A polymer-supported catalyst is generated by adding excess n-BuLi to a benzene suspension of amine-functionalized polystyrene beads. The catalysis is active in enlarging the rings of lactides and 2,5-morpholinediones, leading to a series of cyclic oligoesters and cyclodepsipeptides, respectively. NaBPh₄ is shown to effectively sequester the 18-membered rings due to the complexation of the Na⁺ ions with the suitable-sized rings. The authors also investigate other metallated supports derived from Me₂Mg and Et₂Zn but they are shown to be less reactive than the lithiated support.