Preparation method for N-methyl-4-nitrophthalimide

Abstract

The invention discloses a preparation method for N-methyl-4-nitrophthalimide. The preparation method comprises: firstly cooling fuming concentrated nitric acid to 5-8 DEG C, dropwise adding concentrated sulfuric acid and preparing the mixed acid at 10-15 DEG C; mixing N-methylphthalimide with concentrated sulfuric acid at 0 DEG C with stirring, then dropwise adding the mixed acid, and reacting for 3-4 h; using an extracting agent to extract a nitrated compound obtained in the reaction; layering, separating an upper-layer organic phase and a lower-layer sulfuric acid mother solution; recovering the upper-layer organic phase to obtain N-methyl-4-nitrophthalimide, performing centrifugation filtering and drying to obtain a finished product; and removing water in the lower-layer sulfuric acid mother solution through a drying agent, concentrating and applying to mixing of the mixed acid in the subsequent batch of the nitration reaction. According to the preparation method, by selecting proper low-temperature processing, acid adding sequence, molar ratio of reaction raw materials and the extracting agent, the yield and the purity are improved. The preparation method helps to reduce generation of by-products, improve the operation environment and reduce production cost.

Description

technical field [0001] The invention relates to a synthesis method of a pharmaceutical intermediate, in particular to a preparation method of N-methyl-4-nitrophthalimide. Background technique [0002] N-methyl-4-nitrophthalimide (NMP) is an important intermediate for the synthesis of various monomer dianhydrides of polyimides. [0003] According to domestic and foreign literature reports, the synthetic method of N-methyl-4-nitrophthalimide mainly contains two kinds: a kind of is the alkylation with phthalimide potassium salt and methyl iodide Reaction preparation, or the alkylation reaction with potassium salt diimide of phthalimide and methyl p-toluenesulfonate; another method is based on the ring-opening reaction of phthalic anhydride and methylamine, and then through the Ring-closing reaction of phthalimide, and finally N-methyl-phthalimide is obtained by nitration reaction. [0004] Wherein, the N-methyl-4-nitrophthalimide obtained through the nitration reaction of N-m...

AI Technical Summary

Problems solved by technology

Because this method uses ice water to cool the concentrated sulfuric acid, N-methyl-3-nitrophthalimide will be precipitated and exothermic, resulting in a low yield of about 80%.

Moreover, a large amount of nitrogen dioxide yellow smoke and a large amount of dilute sulfuric acid wastewater will be generated during operation. The operating environment is poor, and it is strongly irritating to the eyes and skin. The amount of acid liquid to be treated is large, and it needs to be neutralized before it can be discharged. The production cost is high.