Observations on the ring opening reactions of 2-methyleneaziridines with acid chlorides and alkyl chloroformates

A variety of 1-alkyl-2-methyleneaziridines react with alkyl chloroformates (MeO2CCl, PhCH2O2CCl) or acid chlorides (AcCl, p-NO2C6H4COCl) at room temperature in nonpolar solvents (CH2Cl2, THF, toluene) to produce ring opened enamide products in moderate to good yields. Mechanistic studies using 3-deuterio-N-(1-phenylethyl)-2-methyleneaziridine suggest the reactions proceed by initial N-acylation to form the corresponding aziridinium cation (e.g. 27) which subsequently undergoes regiospecific ring opening by chloride ion at the sp(3) hybridised aziridine carbon atom to produce the observed products.