New insights in the mechanism of amine catalyzed epoxidation: dual role of protonated ammonium salts as both phase transfer catalysts and activators of oxone.

摘要: Amines have previously been reported to catalyze the epoxidation of alkenes using Oxone (2KHSO5+KHSO4+K2SO4), and significant levels asymmetric induction were observed. From screening a series amines based on 2-substituted pyrrolidines, it has now found that more consistent reproducible results are achieved with HCl salt amine compared itself. Up 66% ee was in 1-phenylcyclohexene. The chiral could be reisolated >90% yield when reactions conducted at −10 °C, indicating integrity maintained during oxidation process. At (S)-2-(diphenylmethyl)pyrrolidine 1 reacted give mixture ammonium salts containing peroxymonosulfate 6b. enantioselectivity obtained this amine·HCl catalyzed process identical observed, true oxidant relative rates cis- a...