MXPA98005934A - Procedure for the obtaining of piridilmetilisotiociana - Google Patents

Abstract

The present invention relates to a novel process for the preparation of pyridylmethyl isothiocyanates of the formula (I), in which R 1 signifies halogen or alkyl with 1 to 4 carbon atoms, in good yields and with high purity, if in a first step it is react amines of the formula (II), in which R1 has the meaning indicated above, with xanthogenates of the formula (III), in which R2 means alkyl with 1 to 4 carbon atoms, preferably methyl or ethyl and M means a metal alkaline, preferably sodium and potassium or means ammonium, if appropriate in the presence of a diluent and in a second step the dithiocarbamates, as well as the formula (IV), are oxidized, in which R1 and M have the meaning indicated above, given case in the presence of a diluent, to give the isothiocyanates of the formula (

Description

PROCEDURE FOR THE OBTAINING OF PYRIDYLMETHYLIDE TIOCYANATES. Field of the invention. The present invention relates to a novel process for the preparation of pyridylmethylisothiostene as well as to new intermediates. Description of the prior art. It is known that pyridylmethylisothiocyanates are obtained by reaction of pyridylmethylamines of the Formula (A) with carbon disulfide and, for example, ethyl chlorocarbonate in the presence of a base, such as for example sodium hydroxide, according to the following reaction scheme: 1) CS2 15 2) CICOOC2Hs Py-CH-NH2 Py-CH2-NCS Base (A) Py = substituted pyridyl, such as by Example 2-chloro-5-pyridyl (see EP-A 0 302 389). However, this process has the disadvantage that carbon disulfide must be used as a reaction partner. It is also formed carbon oxysulfide as a secondary product. REF. 27800 Description of the invention. It has now been found that pyridyl-methylisothiocyanates of the formula (I) are obtained > wherein 0R1 means halogen or alkyl having 1 to 4 carbon atoms, in good yields and with high purity, if in a first step amides of the formula (II) are reacted 0 in which R1 has the meaning indicated above, with xanthogenates of the formula (III) R20-CS-S®M® (IH) wherein R2 means alkyl having 1 to 4 carbon atoms, preferably methyl or ethyl and M means an alkali metal, preferably sodium and potassium or means ammonium, if any in the presence of a diluent and in a second step the dithiocarbamates, thus obtained, of formula (IV) are oxidized wherein R1 and M have the meaning indicated above, if appropriate in the presence of a diluent, to give the isothiocyanates of the formula (I). The pyridylmethylisothiocyanates, obtainable according to the invention, are generally defined by of the formula (I). In this formula it means R1, preferably chlorine or methyl. Surprisingly, according to the process of the invention, the pyridylmethylisothiocyanates of the formula (I) can be obtained in good yields and with High purity, even though it represents, in the xanthogenates of the formula (III), the sulphided residue MSH the clearable group better against the alcoholic moiety R20H and, therefore, the development of the following reaction would be expected in reality. : The reaction according to the invention has the advantage that the carbon disulfide can be desisted as a participant in the reaction. Furthermore, it is a simple conduction of the reaction (absence of exothermic reaction), which takes place without secondary reactions.

If, for example, 5-aminomethyl-2-chloropyridine and potassium methylxanthogenate are used as starting materials as well as hypochlorite bleach (NaOCl) as oxidizing agent, the reaction sequence of the process according to the invention can be schematized. by means of the following formula scheme: The amines of the formula (II), to be used as starting materials in the first step of the process according to the invention, are known (see for example EP-A 0 391 205 or US-P 4 499 097) and / or they can be obtained in a manner and manner known in general. The xanthogenates of the formula (III), to be further employed as starting materials in the first step of the process according to the invention, are known compounds in general. The dithiocarbamates obtainable in the first step of the process according to the invention are generally defined by means of formula (IV). In this formula R1 preferably chlorine or methyl and M preferably means sodium, potassium or ammonium. The dithiocarbamates of the formula (IV) are new and also constitute an object of the present application. Suitable oxidizing agents for the second stage of the process according to the invention are preferably: hypochlorite bleach (sodium or potassium hypochlorite) and copper-II compounds, such as copper sulfate. Suitable diluents for the first stage of the process according to the invention are customary organic solvents. These include, for example, hydrocarbons, such as toluene or xylene; ethers such as methyl tert-butyl ether, methyl tert-amyl ether, 1,2-methoxyethane, 1,2-diethoxyethane, tetrahydrofuran or dioxane; alcohols, such as methanol, ethanol, n-propanol, i-propanol, n-, i-, s- or t-butanol; nitriles, such as acetonitrile, propionitrile or butyronitrile; as well as amides, such as dimethylformamide. The reaction temperatures in carrying out the first step of the process according to the invention can vary within wide limits. In general, the process is carried out at temperatures between 30 ° C and 150 ° C, preferably at temperatures between 50 ° C and 120 ° C. In the first stage of the process according to the invention, preference is given to equimolar amounts. However, it is also possible to use the xanthate of the formula (III), which is economically priced, preferably in excess of 100%, in a greater excess. The conduct of the reaction, the preparation and the isolation of the novel dithiocarbamates of the formula (IV) are carried out in the manner and manner customary in general (see also the preparation example). Suitable diluents for the oxidation according to the second stage of the process according to the invention are preferably water and a second inert solvent, which is not very miscible with water, such as, for example, hydrocarbons, chlorinated hydrocarbons, ethers, nitriles, ketones or amides. The reaction temperatures in the embodiment of the second stage of the process according to the invention can vary within wide limits. In gene¬ * ral is operated at temperatures between -30 ° C and 50 ° C, preferably at temperatures between -. 10 -10 ° C and 10 ° C In carrying out the second step of the process according to the invention, generally 1 to 4 mol of thiocarbamate, 4 to 5 mol, preferably 4 to 4.5 mol of oxidizing agent are used. The conduct of the reaction, the preparation and the isolation of the pyridyl ethylisothiocyanates of the formula (I) are carried out in the usual manner and manner in general (see also the preparation example). The pyridylmethylisothiocyanates of the formula (I) to be prepared according to the process of the invention can be used as intermediates for the preparation of biologically active compounds, for example insecticides (see for example EP-A 0 302 389).

Eie plos of obtaining. Example 1. (second stage) . 51.3 g (0.2 mol) of 2-chloro-5-pyridylmethyl-potassium dithiocarbamate are dissolved (see first step) in 200 ml of water and combined with 200 ml of methylene chloride. 460 ml of 13% hypochlorite solution (NaOCl) are added dropwise at 0 ° C in such a way that they do not exceed 5 ° C. The mixture is stirred at 0-5 ° C. for 30 minutes, the organic phase is separated off, the aqueous phase is extracted three times with methylene chloride and the combined organic phases are dried with sodium sulfate. After removal of the solvent by distillation, 31.3 g (82% of theory) of 2-chloro-5-pyridyldimethylisothiocyanate are obtained, which is separated by crystallization in the refrigerator cabinet (melting point: 22 ° C). (first stage) . ? 2.85 g (20 mmoles) of 2-chloro-5-aminomethyl-pyridine and 3.2 g (20 mmo¬) are stirred at reflux overnight. ml) of potassium ethylxanthogenate in 30 ml of ethanol. Allow to cool and separate by filtration: 4.4 g (86% of theory) of 2-chloro-5-pyridylmethyl-potassium dithiocarbamate with a melting point of 252 ° C (decomposition) are obtained. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention. The invention having been described as above property is claimed as contained in the following:

Claims (4)

1.- Procedure for obtaining pyridylmethyl isothiocyanates of the formula (I) wherein R 1 means halogen or alkyl having 1 to 4 carbon atoms, in good yields and with high purity, c-ra-t-r -------- b because in a first stage it is they react with amines of the formula (II) Wherein R1 has the meaning indicated above, with xanthogenates of the formula (III) R2 Q-CS- S® M® (III) 25 -alien R2 being alkyl having 1 to 4 carbon atoms, preferably methyl or ethyl and M means an alkali metal, preferably sodium and potassium or means ammonium, if appropriate in the presence of a diluent and in a second step, the thus obtained dithiocarbamates of formula (IV) are oxidized wherein R1 and M have the meaning indicated above, if appropriate in the presence of a diluent, to give the isothiocyanates of the formula (I).

2.- Dithiocarbamates of the formula (IV) characterized because R1 means halogen or alkyl having 1 to 4 carbon atoms and M means an alkali metal or means ammonium.

3. - Process for obtaining the dithiocarbamates of the formula (IV) Wherein R1 and M have the meaning indicated in claim 1, characterized in that amines of the ZZ = ^ formula (II) 15 Wherein R1 has the meaning indicated in claim 1, with xanthogenates of the formula (III) R ^ O-CS-S 0MM® (III) wherein R2 means alkyl having 1 to 4 carbon atoms and M means an alkali metal or means ammonium, if appropriate in the presence of a diluent.

4.- Use of the dithiocarbamates of the formula (IV) * wherein R1 and M have the meaning indicated in claim 2, for the preparation of pyridylmethylisothiocyanate of the formula (I) Wherein R1 means halogen or alkyl having 1 to 4 carbon atoms. SUMMARY OF THE INVENTION The present invention relates to a new process for the preparation of pyridylmethylisothiocyanates of the formula (I) Wherein R1 means halogen or alkyl having 1 to 4 carbon atoms, in good yields and with high purity, if in a first step amine amines are reacted * • 15 formula (II) Wherein R1 has the meaning indicated above, with xanthogenates of the formula (III) R20- -CS- -SG® (III) wherein R2 means alkyl with 1 to 4 carbon atoms, preferably methyl or ethyl and M means an alkali metal, preferably sodium and potassium or means ammonium, if any in the presence of a diluent and in a second stage the dithiocarbamates are oxidized, * obtained, from the formula (IV) wherein R1 and M have the meaning indicated above, if appropriate in the presence of a diluent, to give the isothiocyanates of the formula (I).