background and overview[1]
2-aminomethylbenzimidazole and its salt 2-(aminomethyl)benzimidazole dihydrochloride is a fine chemical raw material with wide application value. as a mild anti-corrosion agent for carbon steel, it is also an intermediate for the synthesis of benzimidazole schiff bases, which have anti-swelling, antibacterial and other activities. the traditional synthesis method of 2-aminomethylbenzimidazole is to use hcl as a catalyst to react o-phenylenediamine and glycine through a multi-step heating and refluxing reaction. its shortcomings include longer reaction time, more side reactions, and lower yield. a method for synthesizing 2-aminomethylbenzimidazole using o-phenylenediamine and glycine using hcl as a catalyst. this method requires heating and refluxing for 72 hours, but the highest yield is 56%. a method of synthesizing 2-aminomethylbenzimidazole using hcl as a catalyst, o-phenylenediamine and glycine as raw materials, and microwave irradiation. this method shortens the reaction time to 7 hours, and the maximum yield is 46%.
preparation[1]
the synthesis method of 2-aminomethylbenzimidazole is to use o-phenylenediamine and glycine as raw materials, hcl as the catalyst, and use microwave intermittent irradiation to perform a condensation reaction to generate 2-aminomethylbenzimidazole in one step. 2-aminomethylbenzimidazole further reacts with hydrochloric acid to form 2-(aminomethyl)benzimidazole dihydrochloride. the reaction equation is as follows:
the specific operation process includes the following steps:
a) take o-phenylenediamine, glycine and 5~6mol/l hcl and add them to the flask in sequence. the molar ratio of o-phenylenediamine to glycine is 1:1~3, preferably 1:1.5~2.5 ; the molar ratio of o-phenylenediamine and 5~6mol/lhcl is 1:10~12. stir evenly, put it into a microwave oven with a frequency of 2450mhz, and irradiate intermittently 6 times at an output power of 119w, 1 minute each time, to completely dissolve.
b) intermittently irradiate the fully dissolved solution 10 times in a microwave oven at an output power of 119~280w, with each irradiation lasting 4~6 minutes followed by a 10-minute pause. cool and precipitate solid, filter, wash with absolute ethanol, and dry to obtain a crude product.
c) the crude product is recrystallized with absolute ethanol to obtain 2-aminomethylbenzimidazole dihydrochloride. dissolve it in water, adjust the ph to 8~9 with ammonia water, cool to 3~5°c, and allow the crystallization was complete and recrystallized from ethanol/water to obtain 2-aminomethylbenzimidazole with a maximum yield of 77%. 2-aminomethylbenzimidazole further reacts with hydrochloric acid to form 2-(aminomethyl)benzimidazole dihydrochloride
main reference materials
[1] cn200910022439.3 a method for synthesizing 2-aminomethylbenzimidazole by microwave irradiation
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