PURPOSE: To obtain a threo-1-azido-1-substituted phenyl-2-aminopropane useful as a raw material for stereoselective synthesis according to a stereoselective method with a substituent group simply by reacting an aziridine derivative having the substituent group with sodium azide.

CONSTITUTION: This method for producing a threo type 2-aminopropane derivative expressed by formula II (Ar is phenyl which may be substituted) is to react a cis type aziridine derivative expressed by formula I with sodium azide. The reaction is preferably carried out in a polar solvent such as dimethyl sulfoxide, dimethyl formamide or alcohols at about 50-80°C. For example, cis-2- methyl-3-(4-methylphenyl)-aziridine expressed by formula III is reacted with the sodium azide by using the reaction to provide threo-1-azido-1-(4- methylphenyl)-2-aminopropane expressed by formula IV. The compound expressed by formula II is useful as an intermediate for agrochemicals and medicines, especially the agrochemicals such as insecticides.