JPS6333359A - Production of isothiocyanate - Google Patents

Abstract

PURPOSE:To safely and easily produce the titled compound useful as a raw material for agricultural chemicals, pharmaceuticals and other chemicals, under mild condition, by reacting an amine with carbon disulfide in the presence of a specific low-toxic reaction accelerator. CONSTITUTION:An amine (e.g. methylamine) is made to react with 2 times equivalent of carbon disulfide in the presence of 1,8-diazabicyclo[5,4,0]undec-7- ene. The reaction is carried out in the absence of solvent or, if necessary, in a solvent such as benzene at -50-+80 deg.C for 5 min-15 hr, preferably at 0-50 deg.C for 0.5-10 hr. The amount of the reaction accelerator is 1.5-5 mol per 1 mol of the amine. The yield of the product can be improved by carrying out the reaction of amine with carbon disulfide in the presence of an alkyl halide.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a novel method for producing isothiocyanates. More specifically, the present invention is directed to the production of isothiocyanates, which are useful as raw materials for agricultural chemicals, pharmaceuticals, and their low-chemical products, through a safe and simple reaction under mild conditions using amines and carbon disulfide as raw materials. Regarding the method.

[Conventional technology]

Isothiadionates are known to be important compounds as raw materials for agricultural chemicals, pharmaceuticals, and their low-chemical products.

This isothiocyanate has conventionally been produced by the following method.

(1) A method in which a primary amine and carbon disulfide are reacted in the presence of a metal oxide such as arsenous acid, mercury oxide, or lead oxide.

(2) A method of producing by reacting a primary amine and carbon disulfide using a Grignard reagent.

However, method (1) requires the use of toxic heavy metal compounds and has the disadvantages of extremely violent exothermic reaction. In addition, since method (2) uses a Grignard reagent, the reaction system must be strictly anhydrous, and the process is complicated, so it cannot be said to be an industrially advantageous method.

[Problem that the invention seeks to solve]

The present invention improves the drawbacks of such conventional isothiocyanate production methods, and uses a less toxic reaction accelerator in the absence of a solvent or in the presence of a small amount of solvent.
The object of the present invention is to provide an industrially advantageous method for producing isothiocyanate, in which the reaction proceeds smoothly under mild conditions and in a simple reaction process to obtain isothiocyanate in good yield.

[Means for solving problems]

As a result of intensive research to achieve the above object, the present inventors used 1,8-diazabicyclo(5,4゜0]unde-7-cene, an ultrabasic organic compound, as a reaction accelerator. It was discovered that the object could be achieved by reacting an amine with carbon disulfide and, if necessary, an alkyl halide, and based on this knowledge, the present invention was completed.

That is, the present invention provides 1,8-diazabicyclo(5,4
.

The present invention will be explained in detail below.

The amine used as a raw material in the method of the present invention is a primary amine.
Both alicyclic amines and aromatic amines can be used, such as methylamine, ethylamine, n-propylamine, 1so-propylamine, n-butylamine, 1so-butylamine, 5ec-butylamine, te
Examples include aliphatic amines such as rt-butylamine, hexylamine, octylamine, laurylamine, and dodecylamine, alicyclic amines such as cyclohexylamine, and aromatic amines such as aniline, toluidine, and benzylamine. These aromatic amines may be substituted with halogen or alkyl groups. Also, 1,3-propylene diamine, 1゜4-tetramethylene diamine, 1,
Polyamines such as 6-hexamethylene diamine, metaxylylene diamine, paraxylylene diamine and the like can also be used.

Another aspect of the present invention is to increase the yield of isothiocyanate by reacting an alkyl halide when reacting an amine with carbon disulfide. When the reaction is carried out in the presence of an alkyl halide, the yield of isothiocyanate increases, but trithiocarbonate is produced as a reaction by-product.

The alkyl halide is preferably alkyl chloride, alkyl bromide, or alkyl iodide, such as methyl chloride, ethyl chloride, n-propyl chloride,
30-propyl chloride, n-butyl chloride, 1
so-butyl chloride, 5ec-butyl chloride,
Examples include alkyl chlorides such as n-hexyl chloride and 2-ethylhexyl chloride, and various bromides and iodites corresponding thereto.

In the method of the present invention, 1°8-diazabicyclo(5,4,0]unde-7-cene (hereinafter referred to as D
(abbreviated as BU) is used.

This compound is an ultra-basic substance with a structure represented by the formula and has extremely basic properties, has extremely excellent catalytic ability, and has the property of being soluble in most solvents.

Next, to explain one example of a preferred embodiment of the present invention, first, in the presence of DBU of preferably 1.5 to 50 moles, more preferably 2 to 5 moles per mole of amine, DBU is added to the amine. Two equivalents of carbon disulfide are reacted. Here, 2-fold equivalent does not mean 2-fold equivalent in the strict sense, but means substantially 2-fold equivalent, and a slight increase or decrease does not matter. At this time, the reaction may be carried out in the absence of a solvent or, if necessary, in the presence of a small amount of a solvent.

Examples of solvents include benzene, toluene, xylene,
Aromatic hydrocarbons such as ethylbenzene, aliphatic hydrocarbons such as n-hexane, alicyclic hydrocarbons such as cyclohexane, etc. can be used.

The reaction temperature is usually -50 to 80°C, preferably 0 to 50°C.
There is no particular restriction on the reaction pressure; the reaction may be carried out under normal pressure or under increased pressure, but when carried out under increased pressure, the pressure is 100 kg /cj-G or less, preferably 50 kg/c
d −G or less is desirable. Further, the reaction time depends on the reaction temperature and the like, but is usually about 5 minutes to 15 hours, preferably about 0.5 to 10 hours.

Next, when reacting an alkyl halide, the alkyl halide is added to the reaction solution in an amount equivalent to twice the amount of the amine (the meaning of "double equivalent" is the same as above). At this time, if necessary, a small amount of a solvent may be added to carry out the reaction, but if a solvent is used in the reaction, it is preferable to use the same solvent.

This reaction temperature is usually -50 to 150°C, preferably 0.
The reaction pressure is selected within the range of ~100°C, and there is no particular restriction on the reaction pressure.The reaction may be performed under normal pressure or under increased pressure. is 100 kg/cIiI-G or less, preferably 50k
g/c+d-G or less is desirable.

Furthermore, the reaction time depends on the amount of DBU used and the reaction temperature, but is usually 0.5 to 24 hours.
Preferably it is about 1 to 5 hours.

In addition, it is preferable to carry out the reaction under an inert gas atmosphere such as nitrogen or argon throughout the entire reaction, but of course the reaction is not limited thereto.

The isothiocyanate in the reaction solution thus produced can be recovered by a commonly used method. For example, the desired isothiocyanate can be obtained by extracting the reaction solution with a solvent such as benzene, washing thoroughly, and then distilling off the solvent. Furthermore, when an alkyl halide is reacted, trithiocarbonate is produced as a by-product.

According to the method of the present invention, isothiocyanates can be industrially produced in good yields under mild reaction conditions in the absence of a solvent or in the presence of a small amount of a solvent.

〔Example〕

EXAMPLES Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples in any way.

Examples 1 to 6 The indicated amounts of amine and DBU were placed in a flask,
10 ml of benzene was added, and while stirring under water cooling, the indicated amount of carbon disulfide and 5 ml of benzene were added dropwise, and the reaction was carried out at the indicated time and temperature. Furthermore, in an example of a method in which an alkyl halide was also reacted, the indicated amount of butyl bromide and 5 ml of benzene were then added to this reaction solution, and the reaction was carried out at the indicated temperature and time.

Next, the reaction completed liquid was extracted three times with 50 ml of benzene, and this extracted layer was washed once with 175 ml of 2N-HC, twice with 50 ml of water, and once with 50 ml of saturated saline.
After drying over anhydrous sodium sulfate, benzene was distilled off under reduced pressure, followed by fractional distillation to obtain isothiocyanate and trithiocarbonate.

The results are shown in the table below.

(The following is a blank space) [Effects of the Invention] The method for producing isothiocyanate of the present invention is a method in which carbon disulfide is reacted with an amine using non-toxic DBU as a reaction accelerator, in the absence of a solvent or in a small amount. This method has high industrial value, as isothiocyanates can be obtained in a simple reaction process with good yields under very mild reaction conditions in the presence of a solvent. It is extremely useful as a raw material for chemical products.

Claims (1)

[Claims] 1,1,8-diazabicyclo[5,4,0]under-7
- A method for producing an isothiocyanate, which comprises reacting an amine with two equivalents of carbon disulfide in the presence of -sen. 2,1,8-diazabicyclo[5,4,0]under-7
- A method for producing an isothiocyanate, which comprises reacting an amine with two equivalents of carbon disulfide and an alkyl halide in the presence of -sen.