Asymmetric epoxidation guanidines

Excellent conversions and selectivities were observed both with respect to the alkene and the primary oxidant [62]. In nitro-Michael reaction it was noted that the Murphy s PTC does not work as a good chiral catalyst for the Michael reaction of chalcone, but the same PTC effectively catalyses the epoxidation of chalcones with sodium hypochlorite (NaOCl) [24c]. Trials for the epoxidation of chalcone in the combination of hydroperoxides and modified guanidines 19 [27b] resulted in less effective asymmetric induction compared to the Murphy s PTC [53] (Scheme 4.21). 

Kumamoto, T., Rhine, K., Endo, M. et al. (2005) Guanidine-catalysed asymmetric addition reactions Michael reaction of cyclopentenone with dibenzyl malonates and epoxidation of chalcone. Heterocycles, 66, 347-359. 

---