Preparation method of 4-nitroindole

Abstract

The invention relates to a preparation method of 4-nitroindole. The method comprises the following steps of: adding 2-methyl-3-nitrobenzene, triethyl orthoformate and oxalic acid into a flask by a certain proportion; heating and refluxing to react for certain time and then cooling to 0-10 DEG C; slowly dropping an alcohol solution of potassium ethoxide; continuing to reacting for a period of time at normal temperature and pouring the reaction liquid into ice water to ensure that a large quantity of solid appears; and sucking and filtering to obtain solid, i.e. the 4-nitroindole. The method has the characteristics of high yield, easy operation, and the like.

Description

technical field

[0001] The invention relates to a preparation method of 4-nitroindole. Background technique

[0002] 4-Nitroindole is an important intermediate for preparing other simple 4-substituted indoles, and is also an important raw material for the synthesis of dyes and drugs. There are many foreign studies on the synthesis method of -nitroindole: for example, 4-nitroindole is synthesized by ring closure of 2-methyl-3-nitroaniline, and 4-nitroindole is produced by hydrolysis after cyclization of m-nitrophenylhydrazone. Nitroindole, 4-nitroindole is prepared from m-dinitrobenzene derivatives, 4-nitroindole is prepared from 4-nitroindoline, etc. What is valuable in the above-mentioned method for synthesizing 4-nitroindole is that 2-yl-3-nitroaniline is the starting material, and 4-nitroindole is prepared by alkali induction under the promotion of dialkyl oxalate . The raw materials of the method are all bulk products, the reaction steps are few, the operation is simp...

Examples

Embodiment 1

[0017] In the flask, 76g of 2-methyl-3-nitrobenzene, 89g of triethyl orthoformate, and 50g of oxalic acid were added, and after heating to reflux for 2 hours, after cooling down to 10°C, slowly dropwise added potassium ethylate (42g) 65g of ethanol solution, after continuing to react at room temperature for 4 hours, the reaction solution was poured into ice water, a large amount of solid appeared, and 60g of solid was obtained by suction filtration, which was 4-nitroindole, with a yield of 74%.

Embodiment 2

[0019] In the flask, 76g of 2-methyl-3-nitrobenzene, 115g of triethyl orthoformate, and 70g of oxalic acid were added, and after heating to reflux for 4 hours, after cooling down to 10°C, slowly dropwise added potassium ethylate (51g) 80g of ethanol solution was continued to react at room temperature for 4 hours, then the reaction solution was poured into ice water, a large amount of solid appeared, and 66g of solid was obtained by suction filtration, which was 4-nitroindole, with a yield of 81.4%.

technical field

[0001] The invention relates to a preparation method of 4-nitroindole. Background technique

[0002] 4-Nitroindole is an important intermediate for preparing other simple 4-substituted indoles, and is also an important raw material for the synthesis of dyes and drugs. There are many foreign studies on the synthesis method of -nitroindole: for example, 4-nitroindole is synthesized by ring closure of 2-methyl-3-nitroaniline, and 4-nitroindole is produced by hydrolysis after cyclization of m-nitrophenylhydrazone. Nitroindole, 4-nitroindole is prepared from m-dinitrobenzene derivatives, 4-nitroindole is prepared from 4-nitroindoline, etc. What is valuable in the above-mentioned method for synthesizing 4-nitroindole is that 2-yl-3-nitroaniline is the starting material, and 4-nitroindole is prepared by alkali induction under the promotion of dialkyl oxalate . The raw materials of the method are all bulk products, the reaction steps are few, the operation is simp...

Examples

Embodiment 1

[0017] In the flask, 76g of 2-methyl-3-nitrobenzene, 89g of triethyl orthoformate, and 50g of oxalic acid were added, and after heating to reflux for 2 hours, after cooling down to 10°C, slowly dropwise added potassium ethylate (42g) 65g of ethanol solution, after continuing to react at room temperature for 4 hours, the reaction solution was poured into ice water, a large amount of solid appeared, and 60g of solid was obtained by suction filtration, which was 4-nitroindole, with a yield of 74%.

Embodiment 2

[0019] In the flask, 76g of 2-methyl-3-nitrobenzene, 115g of triethyl orthoformate, and 70g of oxalic acid were added, and after heating to reflux for 4 hours, after cooling down to 10°C, slowly dropwise added potassium ethylate (51g) 80g of ethanol solution was continued to react at room temperature for 4 hours, then the reaction solution was poured into ice water, a large amount of solid appeared, and 66g of solid was obtained by suction filtration, which was 4-nitroindole, with a yield of 81.4%.