PROCESS FOR PREPARING THIOPHENE AND ITS DERIVATIVES

Abstract: In the process according to the invention for the preparation of thiophene and particularly a thiophene, the non-sulphur bound carbon of which is substituted, the product is produced by treating succinic anhydride or especially substituted succinic anhydride with a sulphur compound. The sulphur compound is preferably a sulphur compound, which contains phosphorus, such as phosphorus pentasulphide. The stated treatment with a sulphur compound forms according to one embodiment the end stage of the process, in which 1-alkene is attached to maleic anhydride to give an 1-alkenyl-succinic anhydride, the 1-alkenylsuccinic anhydride is hydrogenated catalytically to produce an alkylsuccinic anhydride and the alkylsuccinic anhydride is treated with the above-mentioned sulphur compound to give a thiophene, the non-sulphur bound carbon of which, e.g. 3-carbon, is substituted.

Description: Process for preparing thiophene and its derivatives The invention relates to a process for the preparation of 3- alkylthiophene. It is generally known that the preparation of 3-substituted thiophene is more difficult than the preparation of 2- substituted thiophene. 3-substituted thiophene is, however, a desirable intermediate or end product in various appli¬ cations, such as a herbicide or fungicide. Certain 3- substituted thiophenes can also be used as monomers in the preparation of e.g. electrically conductive polymers. 3-substituted thiophene can, in principle, be prepared through two different routes: by using thiophene or thiophene with a modifiable 3-substituent as starting material or by using an acyclic compound as the starting material. Substituted thiophenes can, of„ course, also be prepared by other means, but the products are then in most cases 2-substituted. The best known method of preparing 3-substituted thiophene by using thiophene as starting material is the bromination of thiophene. Bromine is added in about a threefold excess, whereby the bromine attaches both to the more reactive positions 2 and 5 and the position 3 mentioned, or to the positions 3 and 4. The bromine substituents in the positions 2 and 5 can then be reduced away with zinc and glacial acetic acid (Gronowitz, S. and Raznikiewicz, T. Org. Synth. 44 (1964), 9). 3-bromothiophene can be prepared cata¬ lytically technically more advantageously from 2.5-dibromo- thiophene and thiophene (Grosvenor, P.G., Fuller, L.S., EP 299,586). 3-bromothiophene is one of the most important intermediates for a wide selection of 3-substituted thiophenes, e.g. by using Grignard reactions, lithiation or oxidation. The use of 3-bromothiophene as a starting material in processes of production is seriously limited by formation of non-desirable bromides and by difficult reaction conditions, such as an unsuitable temperature and an inert atmosphere. The preparation of 3-substituted thiophene by using an acyclic compound has been widely studied. These methods often have the drawback that they produce a lot of 2- substituted thiophenes as by-products. Among these methods the use of various mercaptans or thioethers as the starting material should be mentioned (Butler, A.R. , Henry, J.B., J. Chem. Soc, B, 1970 or Campaigne, E., Monroe, P. ., J. Am. Chem. Soc, 76 (1954), 2445). 3-substituted thiophene can also be prepared from other compounds containing either double-bonds or other functional groups (Veal, K.T., Grinter, T.J., EP 38121 or Duus, F., Tetrahedron, 32 (1976), 2817) . As has been stated above, many of these processes, known to those skilled in the art, produce large amounts of undesirable 2-substituted thiophene compounds and isomers, the separation of which causes difficulties. Moreover, the undesirable by-products originate from the same starting material so the yield in the methods of prior art remains very low. Thus, the object of the present invention is to provide the most selective method for the preparation of 3- alkylthiophene. A further object is a method for the preparation of 3-alkyl-thiophene, where the yield and purity grade are as high as possible. The above-mentioned objects have now been obtained by using a method for the preparation of 3-alkylthiophene, which is mainly characterized by what is stated in the characterizing clause of the patent claim 1. It has thus been realized that 3-substituted thiophene, such as 3-alkylthiophene, is produced with high yield and great selectivity if the method for its preparation comprises a treatment of substituted, such as alkylsubstituted, succinic anhydride with a sulphur compound which contains phosphorus. The treatment of a substituted succinic anhydride with a sulphur compound can as such form the method of preparation or then it can form a reaction step in a process, the starting materials of which are other than said alkyl- succinic anhydride. The treatment with a sulphur compound which contains phosphorus is preferably carried out by heating an alkylsuccinic anhydride together with a sulphur compound which contains phosphorus, by adding an alkali solution to the cooled reaction mixture, by extracting the reaction product with ether and by evaporating the ether from the ether phase, leaving the desired 3-alkylthiophene. The treatment is carried out with a sulphur compound con¬ taining phosphorus, which converts the acid anhydride to diene sulphide. .Among preferable sulphur compounds count e.g. 2,4-bis( -methoxyphenyl)-1,3,2,4-dithiaphosphethane- 2,4-disulphide or phosphorus pentasulphide. Phosphorus pentasulphide can be used as such or as a mixture together with an alkali metal sulphide or in a solvent such as in pyridine or acetonitrile. According to the invention the treatment with a sulphur compound, which contains phosphorus, is directed to an alkyl- succinic anhydride. Hereby, it is preferable that the alkyl-succinic anhydride is prepared by catalytic hydrogenation of an 1-alkenylsuccinic anhydride. The 1- alkenylsuccinic anhydride, on the other hand, is preferably prepared by adding an 1-alkene to maleic anhydride. One preferred embodiment of the invention comprises com¬ bining of the above-mentioned stages so that: a) an 1-alkene is added to maleic anhydride in order to produce an 1-alkenylsuccinic anhydride; b) the 1-alkenylsuccinic anhydride is hydrogenated cata- lytically to produce an alkylsuccinic anhydride; and c) the alkylsuccinic anhydride is treated with a sulphur compound, which contains phosphorus, to produce a 3- alkylthiophene. In the stage of the synthesis where the 1-alkene is attached to the maleic anhydride, it is advantageous to attach only one 1-alkene per mole of maleic anhydride. A preferred 1- alkene is l-C 3 -C 20 -alkene and the most preferable is 1-C 8 -C 20 - alkene, such as 1-octene or 1-dodecene. The stage where the alkylsuccinic anhydride is prepared, is a fairly conventional catalytical hydrogenation stage. As catalyst can be used e.g. a palladium carbon catalyst. In the following some examples are presented for the carrying out of the invention, the purpose of which are only to illustrate the present invention. Example 1 Alkenylsuccinic anhydride Maleic anhydride (14 g, 0.14 moles) and 1-octene (50ml, 032 moles) were fed into an autoclave. The mixture was treated with nitrogen. The reaction mixture was heated at a tempera¬ ture of 210°C for 4 hours. After cooling the mixture was filtrated and the excess of the octene was removed by vacuum evaporation. The yield of octenylsuccinic anhydride was 25g (85% of the theoretical amount). Example 2 Alkenylsuccinic anhydride The procedure was similar as in example 1, except that the amount of octene used was 30ml (0.19 mole), whereby the yield was 80% of the theoretical amount. Example 3 Alkylsuccinic anhydride The octenylsuccinic anhydride obtained was dissolved in ethyl acetate and hydrogenated by using a palladium/carbon catalyst (5% by weight of the starting material). The cata- lyst was filtrated and the solvent was evaporated. The yield of the octylsuccinic anhydride was 24g (95% of the theoreti¬ cal amount) . Example 4 Alkylsuccinic anhydride The procedure was similar as in example 3, except that dodecyl succinic anhydride, which had been prepared substan- tially in the same manner as in the examples 1 and 2, and 1% by weight of a palladium/carbon catalyst were used. The yield was the same as in example 3, i.e. 95% of the theor¬ etical amount. Example 5 3-Dodecyl hiophene 12g of dodecylsuccinic anhydride and 17g of phosphorus pentasulphide were heated together on an electric pad. After having reached a sufficiently high temperature, i.e. about 140°C, the mixture reacted violently turning simultaneously black. At this stage the heating was disconnected. Sodium hydroxide solution was added into the cooled mixture and the product was extracted with ether. The ether phase was dried with sodium sulphate and the ether was evaporated, giving 9g of raw product. The purity of the product was 80% and the yield was 64%. The MR-spectrum of the starting material, i.e. the dodecylsuccinic anhydride, is presented in Figure 1 and the NMR-spectrum of the product, i.e. the 3-dodecyl- thiophene, in Figure 2. The mass spectrum of the product, i.e. the 3-dodecylthiophene, is presented in Figure 3. Example 6 3-Octylthiophene The procedure was similar as in example 5, except that instead of dodecylsuccinic anhydride octylsuccinic anhydride was used and as the solvent of the mixture xylene was used. The yield was 35%.

Claims: Claims 1. A process for the preparation of 3-alkylthiophene, characterized in that it comprises the treatment of alkyl- succinic anhydride with a sulphur compound, which contains phosphorus. 2. A process according to claim 1, characterized in that the treatment with the sulphur compound is carried out by heating alkylsuccinic anhydride together with a sulphur compound, which contains phosphorus, by adding alkali solution to the cooled reaction mixture, by extracting the reaction product with ether and by evaporating the ether from the ether phase. 3. A process according to claim 1 or 2, characterized in that the treatment is carried out with a phosphorus sulphur compound, which is phosphorus pentasulphide. 4. A process according to any of the preceding claims, characterized in that the alkylsuccinic anhydride is pre¬ pared by catalytic hydrogenation of an 1-alkenylsuccinic anhydride. 5. A process according to claim 4, characterized in that the 1-alkenylsuccinic anhydride is prepared by adding an 1- alkene to maleic anhydride. 6. A process according to any of the preceding claims, characterized in that it comprises the following stages: a) 1-alkene is added to maleic anhydride in order to produce 1-alkenylsuccinic anhydride; b) the 1-alkenylsuccinic anhydride is hydrogenated cata¬ lytically to produce an alkylsuccinic anhydride; and c) the alkylsuccinic anhydride is treated with a sulphur compound, which contains phosphorus for preparing the 3- alkylthiophene. 7. A process according to any of the claims 4 to 6, characterized in that one mole of 1-alkene is added to the maleic anhydride per mole of the latter. 8. A process according to any of the claims 4 to 7, characterized in that the 1-alkene to be added is 1-alkene is an l-C 3 -C 20 -alkene and preferably an l-C 8 -C 20 -alkene, such as 1-octene or 1-dodecene.

Inventors: HEINOLA KALEVI, HORMI OSMO, KARJALAINEN SARI, KOSKIMIES SALME, LAHTINEN LEILA, MONONEN PIRJO, NAESMAN JAN, NYHOLM PER, PARKKINEN LEA, TAMMI ANNA-LIISA, TUOMINEN SIMO, HEINOLA, KALEVI, HORMI, OSMO, KARJALAINEN, SARI, KOSKIMIES, SALME, LAHTINEN, LEILA, MONONEN, PIRJO, NAESMAN, JAN, NYHOLM, PER, PARKKINEN, LEA, TAMMI, ANNA-LIISA, TUOMINEN, SIMO
Applicants: NESTE OY
Application year: 1992
Main classification: C07D333
IPC codes: C07D333