Abstract
In this paper,an expeditious and efficient continuous-flow process is reported for the synthesis of syn-2-amino-,3-diol.The starting material syn-2-nitro-1,3-diol reacts with hydrogen gas in a micro fixed-bed reactor packed with a Raney Ni catalyst to provide syn-2-amino-1,3-diol in 93% isolated yield.The reaction time in the flow system was markedly reduced(from 36 h in batch to 5 min in flow) due to enhanced mass transfer.The effects of the catalyst,solvent,reaction temperature,reaction time,pressure,and H2 flow rate have been investigated successively.The optimum conditions for the continuous-flow reaction are described as follows when using Raney Ni as a catalyst at a reaction temperature of 25 ℃,a reaction pressure of 10 bar,a reaction solvent of 3% AcOH in methanol,an H2 flow rate of 25 sccm,and a liquid flow rate of 0.6 mL/min.The reaction kinetics in the temperature range of 10-40 ℃ were investigated.The reaction rate constants and activation energy were determined.The continuous flow system allows for an efficient hydrogenation of syn-2-nitro-1,3-diol on the hectogram scale,corresponding to an overall productivity of 73.6 g/d after continuous operation for over 240 h.
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