A New Preparation Process For (±)-2-Aminopropanol

(S)-(+)-2-Aminopropanol is the key intermediate of synthesizing antibacterial levofloxacin. At present, it is prepared by reduction, using the corresponding optics active L-Alanine, as material. The product by this method is short of competition because of costly reducer. In this paper, the manufacturing process of synthesizing the externally compensated compound of (S)-(+)-2-Aminopropanol —(±)-2-Aminopropanol by two steps reaction, Propylene oxide (PO), as starting material, has been studied. This synthetic method includes two processes: preparing 2-Chloro-1-propanol by PO in ring-opening reaction with Hydrogen chloride and synthesizing (±)-2-Aminopropanol by aminolysis of 2-Chloro-1-propanol.In ring-opening reaction, the effect of each factor, such as temperature, the molar ration of feed-in about PO versus Hydrogen chloride, the molar ratio of the dilutedness about PO versus aether, time, stiring speed has been studied by orthogonal experiment. The optimum process conditions are found. Thus, reacting at 55℃~ 65 ℃ for 7h with n(PO):n(Hydrogen chloride) = 1:2~1:4, n(PO):n(aether) = 1:1.5, under the 200circle/min of stiring speed , the conversion of PO is 73.98%, the selectivity of 2-Chloro-1-propanol is 43.83% and the yield of 2-Chloro-1-propanol is 32.43%.In reaction of aminolysis of 2-Chloro-l-propanol, using ethanol as solvent and the KI as catalyst, the effect of each factor, such as temperature, time, the molar ration of feed-in about 2-Chloro-1-propanol versus ammonia has been studied by orthogonal experiment. The optimum process conditions are found. Thus, reacting at 110℃~ 120 ℃ for 24h(even more time) with n(Chloropropanol):n(ammonia) = 1:20, the conversion of 2-Chloro-1-propanol is 76.31%, the selectivity of (±)-2-Aminopropanol is 93.67% and the yield of (±)-2-Aminopropanol is 71.48%.The total yield of (±)-2-Aminopropanol is 23.18% under above experimental conditions. At the same time, the mechanism about the ring-opening reaction and aminolysis reaction has been investigated and the experimental results in first step reaction which the main product is 1-Chloro-2-propanol but 2-Chloro-1-propanol have been explained rationally.In addition, the separating conditions and the revised factors of gas chromatography for analyzing reactant components are determined.