DE2309379A1 - Insecticide carbofuran prodn - from 2,3-dihydro-2,2-dimethyl benzofuran - Google Patents

Abstract

Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofur anyl N-methylcarbamate), a known insecticide, is produced in a simple manner and in improved yields by (a) reacting 2,3-dihydro-2,2-dimethyl-benzofuran with an organo Li cpd. (b) treating the resulting 7-lithio cpd. with O2 or an O2-contg. gas (c) hydrolysing the product to give 2,3-dihydro-2,2-dimethyl-7-hydroxy-benzofuran and (d) reacting this with methyl isocyanate.

Description

Method of Making Carbofuran The invention relates to on a process for the production of carbofuran.

Carbofuran (2, 3-dihydro-2, 2-dimethyl-7-benzofuranyl N-methyl carbamate) can be used as an insecticide, as is well known, but so far had the economical one Disadvantage that it is relatively expensive compared to other commercially available ones comparable insecticides. It is known that using carbofuran Pyrocatechol (catechol) can be produced as a starting material.

However, catechol is relatively expensive and because it is contains two hydroxyl groups, there is a particular tendency to form large ones Amounts of undesired by-products and the overall yield of the desired product is relatively low. There are also known methods by which carbofuran under The use of o-chlorophenol or o-nitrophenol is produced, However these processes have the disadvantage that numerous process stages are required and that therefore the overall yield of the desired product is low.

It has now been found that carbofuran is much easier and with higher Yield than previously can be produced if 2, 3-dihydro-2, 2Dimethylbenzofuran is used as the starting material.

According to one embodiment of the invention, the method for Production of carbofuran following process steps: (1) the 2,3-dihydro-2,2-dimethylbenzofuran is made to react with an organolithium compound; (2) the received Lithium adduct is treated with oxygen or an oxygen-containing gas; (3) the product obtained is hydrolyzed to give 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran to obtain; (4) the hydroxy compound is reacted with methyl isocyanate, to obtain 2,3-dihydro-2,2-dimethyl-7-benzofuranyl N-methyl carbamate.

A process for the preparation of 2,3-dihydro-2,2-dimethyl-7-benzofuranyl N-methylcarbamate preferably comprises the following process steps (1) the 2,3-dihydro-2,2-dimethylbenzofuran is mixed with an organolithium compound Li X for Brought reaction, wherein X is an alkyl with 1 to 8 carbon atoms in the chain or a cycloalkyl with up to 6 carbon atoms. The compound 2,3-dihydro-2,2-dimethyl-7-Li-benzofuran is formed, which has the following structural formula (2) the 2,3-dihydro-2,2-dimethyl-7-Li-benzofuran is reacted with oxygen or an oxygen-containing gas (3) the reaction product is acidified and 2,3-dihydro-2,2- dimethyl-7-hydroxybenzofuran, which has the following structural formula (4) the 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran is reacted with methyl isocyanate to form 2,3-dihydro-2,2-dimethyl-7-benzofuranyl N-methyl carbamate, which follows Has structural formula from which the named carbamate is obtained.

The above process step (1) of the reaction of 2,3-dihydro-2,2-dimethylbenzofuran with the organolithium Connection should preferably be in one inert or substantially inert atmosphere are carried out, for example in an atmosphere of nitrogen or argon.

It is desirable that the content of water, oxygen and carbon dioxide is regulated to the lowest possible value in order to avoid a larger amount of undesirable Avoid side reactions. The temperature of the reaction is not very critical and a temperature range of -30 ° C to +150 ° C is suitable. Temperatures in that The range from -10 OC to +50 OC, for example from +10 OC to 40 OC, is particular suitable. Although the reaction can be carried out in the absence of a solvent it is usually more advantageous to carry out the reaction in the presence of an inert solvent or a mixture of inert solvents. To the appropriate Solvents include hydrocarbons and ethers, such as aliphatic Hydrocarbons such as hexane and decane and cyclic ethers such as tetrahydrofuran.

Suitable organolithium compounds include the lithium-alkyl compounds, for example butyllithium, which is particularly suitable, ethyllithium and amyllithium. Cyclohexyllithium is also suitable.

The organolithium compounds can be in the form of a suspension can be used, e.g. the compounds can be suitably dissolved in a hydrocarbon solvent, such as hexane or ligroin. But it can also be the organolithium Compounds in the reaction vessel itself (in situ) made of lithium and a suitable one organic compound. Alkyl or cycloalkyl halides are suitable and preferably alkyl chloride or cycloalkyl chloride. The reactants can are present in stoichiometric ratios, but it is more advantageous if there is an excess of the organolithium compound in the reaction mixture. The reaction time depends on the reaction conditions, for example the temperature of the reaction, the degree of stirring or the concentration of the reactants.

It has been found that suitable yields are achieved when the Reaction at a temperature in the range from 25 ° C. to 40 ° C. for several hours is carried out for a long time.

In the above process step, the reaction mixture preferably stirred while oxygen or an oxygen-containing gas, e.g. Air is passed through the mixture (2). Moisture and carbon dioxide should be kept as far away as possible from the reaction vessel and therefore it is desirable that the oxygen or the oxygen-containing gas is dried and that the carbon dioxide is previously removed from this gas. It was found that part of the solvent is entrained in the gas stream, and the entrained solvent, which has been removed from the reaction mixture in this way, thereafter for more Use can be recovered from the gas.

In process step (3) of the process, the reaction mass is acidified made in the usual manner in an aqueous medium. Such a medium serves as a means for the decomposition of real amounts of the organolithium compound, which can still be present, and also provides a medium for the solution of the MetILphenats. The type of The acid used is not very critical and it can for example hydrochloric acid, sulfuric acid, carbonic acid, acetic acid or chioracetic acid be used. Although the acidation can be carried out at elevated temperatures can, the reaction is mostly at a temperature in the range of 0 0C to 40 0C carried out, preferably at room temperature, at which the reaction within has essentially expired in a short time.

The process step (4) of the above process requires carrying out a reaction at ambient temperature in an inert solvent, for example in diethyl ether, in the presence of a catalyst, for example a tertiary amine such as triethylamine. The desired product can then be selected separated from the reaction mixture and purified in a known manner, for example by crystallization.

The process can be carried out in batches, in a semi-continuous or be carried out in a continuous process.

If desired, the various interconnections can be made after one or more of suitable process steps of the reaction from the reaction medium be separated. However, it is more advantageous not to use the metal interconnects to separate. It is also not essential to use 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran to isolate prior to reaction with the methyl isocyanate, although it may be can also be isolated and purified in the usual way before the further reaction. It should be noted that the yield and cost of the desired Product to some extent on the order of magnitude of the used Depending on the procedure and the degree to which the unreacted material is present in the individual Process steps is recovered and reused. They continue to hang from the recovery and reuse of solvents and gases, which are used in the process and the cost of handling and Obtaining the substances that are produced during the process.

The procedure for converting 2,3-dihydro-2,2-dimethylbenzofuran to 2,3-dihydro-2, 2-dimethyl-7-benzofuranyl N-methylcarbamate is therefore advantageous because in this way the 2,3-dihydro-2,2-dimethyl-7-benzofuranyl N-methylcarbamate can be manufactured much cheaper and more easily and obtained in greater yield than was previously possible. This has the further advantage that as a result the lower cost of the desired product makes it much more economical to use in the destruction and control of unwanted insects and that it is therefore as a substitute for the cheap insecticides made from chlorinated hydrocarbons offers, which are now being used to a large extent in some countries introduced.

The invention will now be described on the basis of exemplary embodiments in which all parts and percentages are by weight when this is not stated otherwise.

Example 1 A dispersion of 3.6 g lithium in 3.6 g paraffin wax was placed in a reaction vessel and 18.5 g of 2,3-dihydro-2,2-dimethylbenzofuran and added 250 ml of dry hexane. The mixture was refluxed for 5 minutes long in an atmosphere of dry nitrogen that has been purified to remove impurities to remove in the form of oxygen and carbon dioxide, cooked. The contents of the reaction vessel was then cooled to 35 0C and a solution of 23 g of n-butyl chloride in 50 ml of dry Add hexane dropwise to the stirring reaction mixture over a period of Added for 1 hour. The contents of the reaction vessel were then left for an additional 2 hours stirred and kept at a temperature in the range of 35 ° C to 38 ° C. Of the The contents of the reaction vessel were cooled to 0 ° C. and then dry air released of carbon dioxide was added through the contents of the reaction vessel for 30 minutes passed this temperature at a rate of 40 ml per minute. The temperature the contents of the reaction vessel were then increased to 20 ° C. and the bubbling through of dry, purified air for another 16 hours at the same speed continued. The contents of the reaction vessel were then stirred and water was added. The water was initially added dropwise and carefully to the stirred Contents added and then the rate of water addition increased'bits overall 200 ml of water were added. The mixture thus obtained was poured into a separatory funnel filled in and the aqueous phase separated from the non-aqueous phase. The non-aqueous Phase was extracted with 100 ml of an aqueous 8% sodium hydroxide solution and the alkaline aqueous extract thus obtained with the above-mentioned aqueous extract Phase united. The combined aqueous phases were then extracted with hexane and the hexane extract is added to the above-mentioned extracted non-aqueous phase, the extracted combined aqueous phases with concentrated hydrochloric acid up to acidified to pH 1 and then extracted with ether. The acid extracted with ether aqueous phase was discarded.

The ether extract was washed with saturated aqueous sodium bicarbonate solution extracted, then washed with water, dried and filtered. The ather became then evaporated, 10 g of a light brown oil were obtained, from which by fractional vacuum distillation 7.3 g of a colorless oil with a boiling point from 81 to 82 ° C. at 1.1 mm mercury pressure. The product thus obtained was identified by thin layer chromatography, infrared spectroscopy and nuclear magnetic resonance as 2,3-dihydro-2, 2-dimethyl-7-hydroxybenzofuran, the can be used as an intermediate for the production of carbofuran. 8 g of the unreacted 2,3-dihydro-2,2-dimethylbenzofuran were from the combined non-aqueous phases and the hexane extract as mentioned above, recovered.

Example 2 In the reaction vessel, in which an atmosphere of dry Nitrogen was maintained, which was purified to remove impurities in the form To remove oxygen and carbon dioxide, 10 g of 2,3-dihydro-2,2-dimethylbenzofuran and 300 ml of dry tetrahydrofuran and mixed. The mixture was stirred at 20 ° C and then to the mixture 100 ml of a 2.4 molar solution of butyllithium in dry hexane added. The stirring was still going on Continued for 1 hour and then another 40 ml of the butyllithium solution added to the mixture.

Stirring the reaction mixture was continued for an additional 21 hours a temperature in the range of 18 0C to 22 0C, after which drier Oxygen through the reaction mixture for 3 hours in an amount of 40 ml per Minute was passed. The contents of the reaction vessel were then stirred and water added. The water was first added dropwise and carefully to the stirred The contents of the reaction vessel are added and the water addition rate is slowly increased until a total of 400 ml of water were added.

The mixture thus obtained was then according to the general procedure, as described in Example 1, processed further and gave 4 g of a light brown Oil, from which 2.9 g of a colorless oil are obtained by fractional vacuum distillation which was determined by thin layer chromatography, infrared spectroscopy and magnetic Nuclear magnetic resonance was identified as 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran.

Example 3 To a cold solution of 8.2 g of 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran, which was produced by the method according to Example 1 and which in 10 ml of diethyl ether was dissolved, were 0.05 g of triethylamine and 2.9 g of methyl isocyanate added. The mixture was stirred at room temperature for 15 minutes until a white crystalline product failed. At the breakup revealed a solid in an amount of 8.8 g in the form of a product having a melting point from 151 to 152 ° C, which by means of Flmentaranalyæe, infrared spectroscopy and magnetic wernresonanz identified as 2,3-dihydro-2, 2-dimethyl-7-benzofuranyl ìq-methylcarbamate became.

Example 4 The general procedure of Example 1 was repeated, however, the n-butyl chloride of this example was replaced with 27 g of n-amyl chloride. In this way, 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran was obtained.

Example 5 The general procedure of Example 1 was repeated, however, the n-butyl chloride in this example was replaced with 30 g of cyclohexyl chloride. There was thus obtained 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran.

10 claims

Claims (10)

Claims: 1.) Process for the production of carbofuran, g e k e n n -z e i c h n e t by the following process steps (1) 2,3-dihydro-2,2-dimethylbenzofuran is made to react with an organolithium compound; (2) the received Lithium adduct is treated with oxygen or an oxygen-containing gas; (3) the product obtained is hydrolyzed to give 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran to obtain; (4) the hydroxy compound is reacted with methyl isocyanate, to obtain 2,3-dihydro-2, 2-dimethyl-7-benzofuranyl N-methyl carbamate. 2.) The method according to claim 1, characterized in that as an organolithium Compound Li X is used, wherein X is an alkyl of 1 to 8 carbon atoms in the chain or a cycloalkyl with up to 6 carbon atoms. 3.) The method according to claim 1, characterized by the following process steps: (1) 2,3-dihydro-2,2-dimethylbenzofuran is reacted with an organolithium compound of the formula Li X, in which X is an alkyl having 1 to 8 carbon atoms in the chain or a cycloalkyl of up to 6 carbon atoms to form the compound 2,3-dihydro-2,2-dimethyl-7-Li-benzofuran, which has the following structural formula (2) the compound 2, 3-dihydro-2, 2-dimethyl-7-Li-benzofuran is reacted with oxygen or an oxygen-containing gas; (3) The reaction product is acidified and the compound 2,3-dihydro-2,2-dimethyl-7-hydroxybenzoruran, which has the following structural formula, is obtained therefrom (4) the compound 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran is reacted with methyl isocyanate to form the compound 2,3-dihydro-2,2-dimethyl-7-benzofuranyl N-methyl carbamate , which has the following structural formula which is separated from the reaction mixture. 4.) The method according to one or more of claims 1 to 3, characterized characterized in that an organolithium compound is used, which from the group xthyllithium, butyllithium and amyllithium was selected. 5.) The method according to one or more of claims 1 to 3, characterized characterized in that cyclohexyllithiu is used as the organolithium compound will. 6.) The method according to claim 3, characterized in that the method step (1) the process is carried out in a substantially inert atmosphere. 7.) The method according to one or more of claims 1 to 6, characterized characterized in that the method in a temperature range from -10 0C to +50 0C is carried out. 8.) The method according to claim 7, characterized in that the method is carried out in a temperature range of +10 0C to + 40 ° C. 9.) The method according to one or more of claims 1 to 7, characterized characterized in that the organolithium compound in the reaction vessel itself (in situ) is generated. 10.) The method according to claim 9, characterized in that the organolithium Compound in the reaction vessel itself from lithium and an alkyl or cycloalkyl halide is formed.