Optical methyl 2-chloropropionate synthesis by decomposition of methyl 2-(chlorocarbonyloxy)propionate with hexaalkylguanidinium chloride hydrochloride

The decomposition of methyl S-(−)-2-(chlorocarbonyloxy)propionate in the presence of hexaalkylguanidinium chloride hydrochloride was confirmed to correspond to a nucleophilic substitution of the second order. However, racemization occured by the contact between the catalyst and methyl R-(+)-2-chloropropionate (). This phenomenon is caused by the exchange between the chloride ion from catalyst and the chlorine atom of () according to a SN2 mechanism as well.