Synthesizing method of (1R,2S)-2-(3,4-difluorophenyl)cyclopropylamine

The invention provides a synthesizing method of (1R,2S)-2-(3,4-difluorophenyl)cyclopropylamine. The synthesizing method comprises the steps that a compound (I) reacts with diethyl cyanomethylphosphonate in the presence of alkaline substances to obtain a compound (II); the compound (II) is subjected to an alkaline oxidation hydrolysis reaction to obtain a compound (III); the compound (III) is subjected to a Hoffman degradation reaction to obtain a compound (IV). According to the synthesizing method, the route is simple, the target product is prepared by taking 2-(3,4-difluorophenyl)ethylene oxide as a raw material through the three reactions of cyclopropanation, oxidative hydrolysis and Hoffman degradation, therefore, the reaction efficiency is greatly improved, the reaction steps are shortened, the operating procedure is simplified, and a novel way is provided for synthesis of a ticagrelor key intermediate; meanwhile, the method is suitable for industrialized production and has the great actual application value and social and economic benefits.