CN101323603A

CN101323603A - Preparation of 2-amido-1,3,4-thiadiazoles

Info

Publication number: CN101323603A
Application number: CNA2008100228224A
Authority: CN
Inventors: 范存逸
Original assignee: RUGAO XINGWU CHEMICAL CO Ltd
Current assignee: RUGAO XINGWU CHEMICAL CO Ltd
Priority date: 2008-07-30
Filing date: 2008-07-30
Publication date: 2008-12-17
Anticipated expiration: 2028-07-30
Also published as: CN101323603B

Abstract

The invention discloses a method for preparing 2-Amino-1,3,4-thiadiazole. Aminothiourea reacts with formic acid under the condition of a catalyst to first generate an intermediate formyl aminothiourea which is decomposed easily; then alkali precipitation is carried out with the existence of ferric oxide, the intermediate formyl aminothiourea is transformed into the 2-Amino-1,3,4-thiadiazole. In the reaction, mixed acid of hydrochloric acid and acetic acid is used as the catalyst which can enhance the yield of the intermediate and accordingly enhance the yield of the final product; the ferric oxide adopted can play the role of regulation and buffering, and lead the alkali precipitation to be carried out smoothly so as to finally obtain 2-Amino-1,3,4-thiadiazole with high purity and high yield.

Description

A kind of 2-amino-1,3, the preparation method of 4-thiadiazoles

Technical field

The present invention relates to a kind of 2-amino-1,3, the preparation method of 4-thiadiazoles.

Background technology

1,3,4 class thiadiazoles are heterogeneous ring compounds that a class is had many uses, and have physiologically active widely, and the Chang Zuowei medicine intermediate is used for preparing sterilant, weedicide, plant-growth adjustment, can also be used to preventing and treating paddy rice blinds rot, bacterial wilt of tomato etc.; In addition because it has aromaticity, and conjugative effect is strong, so also be commonly used to synthetic developer and dyestuff; At present, 2-amino-1,3, the synthetic method of 4-thiadiazoles mainly contains following several in bibliographical information and actual production:

(1) with thiosemicarbazide and the synthetic ware amido thiocarbamide of formic acid reaction, under the vitriolic effect, is dehydrated into ring and generation 2-amino-1,3, the 4-thiadiazoles then.Reaction process is roughly as follows:

This reaction divides to be carried out in two steps, has increased production cost.

(2) hydrochloric acid catalysis one-step technology: in the presence of hydrochloric acid, thiosemicarbazide and formic acid are reacted, and then be dehydrated into ring and generation 2-amino-1,3, the 4-thiadiazoles.

This reaction can one the step finish, but the purity of product and yield are all lower, specifically as seen by happyly grow tall, 5-alkyl-2-amino-1,3 such as Ding Jianhua, 4-thiadiazoles synthetic and use [J]. chemistry world, 2002,23 (4): 576-580.

(3) the new synthetic method in a place is arranged recently, concrete visible Zheng Hao, Dong Huiming, Ding Chenghua, maintain law and order and offer 2-amino-1,3,4-thiadiazoles new synthetic method [J]. He'nan Normal University's journal, 2006,34 (2): 69-70.

Because the oxalic acid price is constantly soaring, last method is not suitable for suitability for industrialized production.

From above summary as can be seen, present existing synthetic method is at preparation 2-amino-1,3, all exist purity lower during the 4-thiadiazoles, the defective that by product is on the high side, and 2-amino-1,3, the 4-thiadiazoles is as intermediate, and the low meeting of its purity influence the yield and the purity of its next step reaction.

Summary of the invention

The invention provides and a kind ofly can make highly purified 2-amino-1,3, the preparation method of 4-thiadiazoles.

In order to solve above technical problem, a kind of preparation 2-amino-1,3 of the present invention, the method of 4-thiadiazoles, it is characterized in that: a kind of 2-amino-1,3, the preparation method of 4-thiadiazoles, it is characterized in that: comprise the following steps: to make thiosemicarbazide and formic acid to generate a kind of easy decomposition intermediate formamido group thiocarbamide under the condition of catalyzer, alkali is analysed in the presence of ferric oxide then, is about to described intermediate and is converted into 2-amino-1,3, the 4-thiadiazoles is characterized in that synthetic route is:

Described catalyzer is the mixing acid that hydrochloric acid and acetic acid are formed.

The mole proportioning of hydrochloric acid and the formed mixing acid of Glacial acetic acid is 100: 3～5 in the described catalyzer.Described last alkali is analysed the use of ferric oxide in the process, and its consumption is 1.8 ‰ of a caustic soda amount-2.5 ‰.

Its content of described thiosemicarbazide is between 95%-97%, and formic acid content is more than 94%.

The present invention mainly divides two aspects:

1. thiosemicarbazide and formic acid are in the process of cyclic condensation, adding can promote the direction of reacting to positive reaction to carry out by mole proportioning 100: 3～5 mixing acid of being formed of hydrochloric acid and acetic acid, this is because when thiosemicarbazide and formic acid reaction, simple hydrochloric acid can only make system keep certain acidity, and makes it fully become the acetic acid that ring must be mentioned in the present invention to exist down; Otherwise can generate a spot of intermediate formamido group thiocarbamide in the reaction process, and its reactive behavior is lower, causes the yield of the finished product to descend.The molecular structural formula of intermediate formamido group thiocarbamide is:

(2) on the other hand in the end alkali analyse in the process, the rate of addition of caustic soda is very big to the influence of product, guarantee that caustic soda is preferentially neutralized by the acid in the system, and do not destroy the structure of product, product too fast or that all can cause generating excessively slowly is converted into thiosemicarbazide again, promptly think the process of a reversible reaction of last existence, and the ferric oxide that is adopted among the present invention can play good adjusting shock absorption, makes alkali analyse process and is carried out smoothly.

Embodiment

Its content of thiosemicarbazide used among the present invention is between 95%-97%, and formic acid content is more than 94%, and the product of gained is specially adapted to the synthetic of dyestuff intermediate, and concrete synthesis step is as follows:

In this method, for cost consideration, preferentially use excessive formic acid, thereby reaction is carried out to the right, and improve the stability of intermediate, used formic acid is excessive to be about 5% to get final product.

In this reaction, in being dehydrated into the process of ring, because a certain amount of water generates arranged,, be beneficial to the carrying out that react, generally adopt the dehydration of distillatory way so must remove these water in the final stage of reaction.

Introduce embodiments of the invention below.

Embodiment 1

Catalyzer only for reaction under the condition of hydrochloric acid is:

In the four-hole boiling flask of 1000mL, add the 152g thiosemicarbazide, 244.8g hydrochloric acid, 95.1g formic acid, be warmed up to 80 ℃ and react half an hour, continue to be warmed up to 105 ℃, be incubated 3 hours, cool to then below 20 ℃, dripping 235g concentration and be 30% NaOH solution, to make the pH of system be 8, then in carrying out crystallization below 10 ℃.

Press above step repeated experiments three times, the results are shown in table 1.

Catalyzer is that reaction is under the condition of mixing acid of hydrochloric acid and acetic acid:

In the reactor of 1000mL, add the 152g thiosemicarbazide, 244.8g the mixing acid of hydrochloric acid and acetic acid (hydrochloric acid and acetic acid mol ratio are 100: 3～5), 95.1g formic acid, be warmed up to 80 ℃ and react half an hour, continue to be warmed up to 105 ℃, be incubated 3 hours, cool to then in 20 ℃, dripping 235g concentration and be 30% NaOH solution, to make the pH of system be 8, then in carrying out crystallization below 10 ℃.

Table 1 is the result of different acid catalyzed reactions

As seen from the above table, at preparation 2-amino-1,3, during the 4-thiadiazoles, the adding of mixing acid can be so that rate improves about 8%.

Embodiment 2 (ferric oxide is analysed effect in the process at alkali)

In the reaction flask of 1000mL, add the 152g thiosemicarbazide, 244.8g the mixing acid of hydrochloric acid and acetic acid (hydrochloric acid and acetic acid mol ratio are 100: 3～5), 95.1g formic acid is warmed up to 80 ℃ and reacts half an hour, continues to be warmed up to about 105 ℃, be incubated 3 hours, add the 2.35g ferric oxide, cool to then in 20 ℃, dropping 235g concentration is 30% NaOH solution, PH is 8, then crystallization below 10 ℃.

Triplicate successively, see the following form with result's contrast of embodiment 2:

Table 2 is the influence of ferric oxide to reaction result

Through repeatedly experiment discovery, the products obtained therefrom outward appearance presents grey, is high purity product.

Claims

1, a kind of 2-amino-1,3, the preparation method of 4-thiadiazoles, it is characterized in that: comprise the following steps: to make thiosemicarbazide and formic acid to generate a kind of easy decomposition intermediate formamido group thiocarbamide under the condition of catalyzer, alkali is analysed in the presence of ferric oxide then, is about to described intermediate and is converted into 2-amino-1,3, the 4-thiadiazoles is characterized in that synthetic route is:

2, a kind of 2-amino-1,3 according to claim 1, the preparation method of 4-thiadiazoles is characterized in that: described catalyzer is the mixing acid that hydrochloric acid and acetic acid are formed.

3, a kind of 2-amino-1,3 according to claim 1, the preparation method of 4-thiadiazoles is characterized in that: the mole proportioning of hydrochloric acid and the formed mixing acid of Glacial acetic acid is 100: 3～5 in the described catalyzer.

4, a kind of 2-amino-1,3 according to claim 1, the preparation method of 4-thiadiazoles is characterized in that: described last alkali is analysed the use of ferric oxide in the process, and its consumption is the 1.8-2.5 ‰ of caustic soda amount.

5, a kind of 2-amino-1,3 according to claim 1, the preparation method of 4-thiadiazoles is characterized in that: its content of described thiosemicarbazide is between 95%-97%, and formic acid content is more than 94%.