Method for preparing N-ethylcarbazole

Abstract

The invention provides a method for preparing N-ethylcarbazole. The method comprises the following steps: dissolving carbazole into N-methylpyrrolidone, and adding a deprotonating agent so as to generate carbazole salt from the carbazole; introducing acetylene so as to generate N-vinylcarbazole from the carbazole salt; adding a noble metal catalyst into the N-vinylcarbazole, and carrying out a hydrogenation reaction so as to obtain a N-ethylcarbazole mother liquor; adding acid into the N-ethylcarbazole mother liquor so as to adjust the pH of the N-ethylcarbazole mother liquor; adding deionizedwater into a pH-adjusted N-ethyloxazole mother liquor so as to obtain a suspension; and subjecting the suspension to standing and filtering, and removing a filtrate so as to obtain the N-ethylcarbazole.

Description

technical field [0001] The invention relates to a method for preparing N-ethylcarbazole, in particular to a method for preparing N-ethylcarbazole in which the solvent can be recovered and used repeatedly. Background technique [0002] 3-Amino-N-ethylcarbazole is an important dye intermediate. The industrial synthesis of 3-amino-N-ethylcarbazole mainly uses carbazole as raw material, which is ethylated to obtain N-ethylcarbazole and then aminated to obtain the product. There are three main existing methods for industrially preparing N-ethylcarbazole: diethyl sulfate method, diethyl carbonate method and haloethane method. [0003] The cost of the alkylating reagent used in the diethyl sulfate method and the diethyl carbonate method is high, and the reaction requires the participation of a toxic solvent, and the reaction yield is not high. The haloethane method mainly uses chlorohexane and bromoethane as the alkylation reagent, the reaction temperature is relatively high, and...

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Problems solved by technology

However, at this reaction temperature, part of DMSO will decompose to produce dimethyl sulfide, giving off a strong odor

CN107488140A discloses a kind of with N-methylpyrrolidone (NMP) as solvent, and acetylene is the method for the preparation of N-vinyl carbazole of alkylating agent, carries out further hydrogenation reaction with palladium catalyst again, the solvent NMP that this method takes The price is expensive, the cost is high, and the stability and solubility of N-ethylcarbazole in NMP are good, and the finished product of N-ethylcarbazole cannot be obtained by cooling crystallization, and the boiling point of NMP is 202 ° C, which is higher than that of NMP. - The boiling point of ethyl carbazole (166°C). If N-ethyl carbazole is obtained by distillation, not only the operation is cumbersome, but too much energy is consumed, and the yield of N-ethyl carbazole finished product is low

This method uses DMF as a solvent, but DMF is unstable under strong alkali conditions and is easily hydrolyzed, so it needs to remove water from DMF before use, which increases the complexity of the experiment, and further recrystallization is required after filtration in the post-treatment In order to obtain the finished product of white N-ethylcarbazole, the cost of the whole process is increased

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