DE2132019A1 - 1,3,4-thiadiazoles - from aldehydes, sulphur and hydrazine - Google Patents

Abstract

of formula: (where R = H, aliphatic, cycloaliphatic, arylaliphatic or aromatic gp.) are prepd. by reaction of an aldehyde of formula: with hydrazine and elementary sulphur. The cpds. are used in the prepn. of plant protection agents and dyes. The starting materials are readily available and good yields and purity are obtd.

Description

Process for the preparation of 1,3,4-hiadiazoles The invention relates to a process for the preparation of 1,3,4-thiadiazoles by reacting aldehydes with hydrazine and elemental sulfur.

It is known from Rodd, Chemistry of Carbon Compounds, Volume IVa, pages 476 ff., To produce 1,3,4-thiadiazoles by reacting diacylhydrazines with phosphorus pentasulfide or cyclizing thiosemicarbazones or acylthiosemicarbazides or reacting dithiocarbazic acid compounds with carbon disulfide or aliphatic aldehydes Processes start from raw materials that are difficult to access, are uneconomical on an industrial scale and give unsatisfactory yields of end products. It has now been found that 1,3,4-thiadiazoles of the general formula can be used in which R denotes a hydrogen atom, an aliphatic, cycloaliphatic, araliphatic or aromatic radical, is advantageously obtained when an aldehyde of the general formula is used in which R has the aforementioned meaning, reacts with hydrazine and elemental sulfur.

The conversion can be represented for the Pall of the use of acetaldehyde and hydrazine hydrate by the following formulas: In comparison to the known processes I, the process according to the invention provides 3,4-thiadiazoles in a simpler and more economical manner in better yield and purity. As a rule, starting material II is reacted with hydrazine and sulfur in a stoichiometric amount. However, it is also possible to use hydrazine and / or sulfur in excess, for example up to a 1.2-fold excess over the stoichiometric amount, based on the aldehyde II. It is expedient to convert hydrazine in the form of its hydrate, but hydrazine itself or its salts, for example the primary or secondary sulfates, are also suitable. If the salts are used, a corresponding amount of a basic compound, e.g. sodium methylate, triethylamine, is added in order to neutralize the acid that forms from the salt during the reaction denotes a hydrogen atom, an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 5 or 6 carbon atoms, an aralkyl group with 7 to 12 carbon atoms or a phenyl group. Alkyl groups with 1 to 4 carbon atoms, being substituted0 As starting materials II zoBo come into question: Benzaldehyde, acetaldehyde, n-butyraldehyde, isobutyraldehyde, propionaldehyde, cyclohexylaldehyde, cyclopentylaldehyde.

The reaction is usually carried out at a temperature of 300C to 1600C, preferably between 600C and 1200C, without pressure or under pressure, continuously or carried out batchwise.

It is expedient to use organic substances which are inert under the reaction conditions Solvents such as aromatic hydrocarbons such as benzene or toluene; Alkanols such as methanol, ethanol, propanols or butanols; Glycol ethers such as glycol monomethyl ether, Glycol diethyl ether, glycol monoethyl ether; or corresponding mixtures. Preferred is a ratio of 2 to 20 moles of solvent per 1 mole of starting material IIo Man optionally uses a tertiary amine as a catalyst, advantageously in one Amount from 0.05 to 0.3 mol based on hydrazine. Preferred catalysts are Trimethylamine, triethylamine, pyridine, N-dimethylaniline, N-diethylaniline, N-ethylpiperidine, N-methylpyrrolidine, a-, ß- and 7-picoline, N-propylpiperidine, quinoline, isoquinoline, Quinazoline, quinoxaline, griamylamine, tri-n-butylamine, n-propyl-diisopropylamine, Trifurfurylamine, trihexylamine, N-methyliinidazole, N-methylpyrrole, N-dimethylcyclohexylamine, Pyrimidine, Acridone, The reaction can be carried out as follows: Starting material II and hydrazine, usually-together with a solvent, are adjusted to the reaction temperature heated and now elemental sulfur is added. The mixture is then left react for another 8 to 16 hours at the reaction temperature. Then the end product separated in the usual way, e.g. by distilling the mixture. The end product if necessary, purified by recrystallization.

In a preferred embodiment of the process, it is left as it is Adding the sulfur to the starting mixture for some time, e.g. 1 to 4 hours the reaction temperature, advantageously at a temperature of 30 to 500C, heated then to 50 to 1600C, preferably to 60 to 12000, and leads with the addition of Sulfur now carries out the reaction in the aforementioned manner The after Compounds which can be prepared by the process of the invention are valuable starting materials for the production of pesticides and dyes.

The parts given in the examples are parts by weight.

Example 1 400 parts of glycol monomethyl ether are used in a stirred apparatus and 400 parts of ethanol are mixed with 264 parts of acetaldehyde.

160 parts of hydrazine hydrate are added to the mixture at 15 to 20 ° given and the mixture is then stirred at 30 ° C. for 2 hours.

0 After heating to 70 ° C, 192 parts of sulfur and 10 parts Triethylamine added. The reaction mixture is then at for a further 15 hours Stirred from 85 to 900C. After cooling to 1500, a small amount is not converted Sulfur is filtered off, the solvent is distilled off and the residue is at 20 Torr fractionally distilled.

At bp20: 97-1000C, 256 parts are 2,5-dimethyl-1,3,4-thiadiazole obtained with m.p. 6400 (from ligroin). The yield corresponds to 75 ffi of theory, based on acetaldehydes used. Example 2 Analogously to Example 1, 144 parts are obtained n-butyraldehyde, 50 parts of hydrazine hydrate, 64 parts of sulfur and 10 parts of triethylamine implemented in 400 parts of alcohol. The reaction mixture is stirred at 80 ° C. for 16 hours After distilling off the solvent 0 UwLrd fractionally distilled at 3 Torr. At boiling point 112-118 ° C., 136 parts of 2,5-di-n-propyl-1,3,4-thiadiazole are obtained The yield corresponds to 80% of theory.

Example 3 Analogously to Example 1, 144 parts of isobutyraldehyde, 50 Parts of hydrazine hydrate and 64 parts of sulfur reacted in 500 parts of glycol methyl ether. The reaction mixture is 14 hours at Stirred at 1050C. At Kp2 92 to 9700, 122 parts of 2,5-diisopropyl-1,3,4-thiadiazole are obtained. The yield corresponds to 72% of theory.

Example 4 Analogously to Example 1, 116 parts of propionaldehyde, 50 Parts of hydrazine hydrate, 64 parts of sulfur and 10 parts of triethylamine in 500 parts Glycol methyl ether reacted At bp3 81 to 850G, 94 parts of 2,5-diethyl-1,3,4-thiadiazole are obtain. The yield corresponds to 66% of theory.

Claims (1)

Claim Process for the preparation of 1,3,4-thiadiazoles of the general formula in which R denotes a hydrogen atom, an aliphatic, cycloaliphatic, araliphatic or aromatic radical, characterized in that an aldehyde of the general formula in which R has the aforementioned meaning, reacts with hydrazine and elemental sulfur.