DD268470A1 - PROCESS FOR THE PREPARATION OF N, N-DIMETHYLTHIAMIDES - Google Patents

Abstract

The invention relates to a novel process for the preparation of N, N-dimethylthiamides which are used as intermediates, in particular for the aralkylcarboxylic acids obtainable by hydrolysis. According to the invention, the title compounds are prepared by reaction of arylalkyl ketones, arylacetylenes or arylalkenes with sulfur and the dimethylammonium dimethylcarbamate obtainable from technically cheap dimethylamine and carbon dioxide at a temperature of 60 to 70 ° C.

Description

Table: Data of the compounds I

TYPE Starting material (II) η Product (I) η Fp ( ⁰ C) Yield (%) No. Ha R 1 R 1 82 81 (D mb H - H 1 82 51 (2) hc H - H 1 82 88 (3) Ha H 1 H 1 72 77 {4) Ha P-CH 1 P-CH ₃ 1 76 70 (5) Ha P-CH ₃ O 1 P-CH ₃ O 1 73 74 (6) Il a p-Cl 2 p-Cl 2 47 » 48 » (7) Ha ' H 3 H 3 51 · 39 · (8th) H H

* The thiamides are not very crystalline, the stated melting points and yields are based on the acids obtained after hydrolysis.

Ausführungsbuisplele The invention will be explained in more detail below with reference to two exemplary embodiments. Example 1: phenylthioacetic acid-N, N-dimethylamide (1)

12.0 g (0.1 mol) of acetophenone (or equivalent amounts of freshly distilled styrene or phenylacetylene), 6.4 g (0.2 mol)

Sulfur and 16.1 g (0.12 mol) Dimethylammoniumdimcthylcarbamat are refluxed for 6 hours (about 6O ⁰ C). The reaction mixture is poured while still hot in 40 ml of hot ethanol, rubs and allowed to crystallize overnight in the cold. The product is filtered off with suction and, if necessary, recrystallised from dilute ethanol. Yield: 14.5g (81%), mp: 82V

(Information ^for styrene or phenylacetylene in the table)

Example 2: β-phenylthiopropionic acid N, N-dimethylamide (7) and hydrolysis to β-phenylpropionic acid 13.4 g (0.1 mol) of propiophenone, 6.4 mol (0.2 mol) of sulfur and 16.1 g (0.12 mol )

Dimethylammoniumdimethylammoniumdimethylcarbamat are refluxed for 12 hours. After cooling, 80 g of 50% strength potassium hydroxide solution in 140 ml of ethanol are added to the batch and heated under reflux for a further 6 hours. The alcohol is then largely distilled off, the residue is diluted with water, filtered and made strongly acidic with concentrated hydrochloric acid. After cooling, extracted three times with 100 ml of ether, the vereinigton extracts dried over magnesium sulfate and the ether evaporated. The β-phenolpropionic acid is recrystallized from water or distilled

 Yield: 7.2 g (48%), mp: 47 ° C, bp: nOT

Claims (3)

1. A process for the preparation of N, N-dimethylthiamides of the general formula I, wherein R may optionally occur repeatedly and a lower aliphatic, optionally du. OH heteroatoms interrupted radical, an alkoxy or dialkylamino group, nitro group or halogen and η is an integer between 1 and 6, characterized in that compounds of the general formula II, in which R and η have the abovementioned structure, are reacted with sulfur and dimethylammonium dimethylcarbamate III without solvent, the carbon dioxide formed during the reaction forming a protective gas cushion. 2. The method according to claim 1, characterized in that is carried out at the temperature of the boiling Dimethylarnmoniumdimethylcarbamates of 60 to 70 ⁰ C. 3. The method according to claim 1, characterized in that the technically cheap dimethylsmin is used in the form of its readily available compound with carbon dioxide as a substitute for high-boiling secondary amines for the thiamides used as intermediates for the preparation of free Aralkylcarbonsäuren. For this 1 page formulas Field of application of the invention The invention relates to a novel process for the preparation of Ν, Ν-dimethylthiamides of general formula I, wherein R may optionally occur repeatedly and a lower aliphatic, optionally interrupted by hetero atoms radical, an alkoxy or nitro group; a differently substituted amino group, halogen or hydrogen and η is an integer between 1 and 6. In addition to their use in the intermediary chemistry, the compounds can be converted, in particular by hydrolysis, into the corresponding co-arylalkanoic acids, which can be used for a wide variety of synthetic purposes, i.a. in bio-drug synthesis, find. Characteristic d * s prior art The previously known process for the preparation of the title products by Willgerodt-Kindler from dimethylamine, sulfur and corresponding aralkyl ketones can be because dimethylamine (boiling point 7 ⁰ C) at room temperature is a gas, only in a closed system under pressure at temperatures of 160 ° C to 180 Kindling C. (K. Kindler, T. Li, Ber., Dtsch. Chem., Ges. 74 [1941J 321; Kindler, Ann. Ann. Chem.431 (19231193).) The Ν, Ν-dialkylthiamides are only intermediates for synthesis Aralkylcarbonsäuren, it is possible to work without pressure with high-boiling amines (usually morpholine), then subjecting the optionally isolated thiamide hydrolysis (reviews: EV Brown, Synthesis 1975, 358; Houben-Weyl, Methods of Organic Chemistry, Bd.E 5 / 2, p.1232, G. Thieme Verlag, Stuttgart-New York 1985) A number of other alternative syntheses based on reactions of derivatives of thio- and dithiocarboxylic acids, the complicated accessibility of these acids of A use limits (p. Scheithauer, R. Mayer, Thio and Dithiocarboxylic Acids and their Derivatives, in A. Senning, Topics in Sulfur Chemistry, Vol. 4, p. 231, G. Thieme Verlag, Stuttgart 1979). Object of the invention The aim of the invention is to make the Ν, Ν-dimethylthiamides accessible at normal pressure and mild temperatures under technically easy-to-control conditions in good yields. Furthermore, a cheaper substitute should be found for the higher-boiling amines for the unintentional Thiamidsynthese. Explanation of the essence of the invention The invention has for its object to develop a novel process for the preparation of Ν, Ν-dimethylthiamides of the general formula I, wherein R and η have the abovementioned meaning, under atmospheric pressure ur ^ to develop at mild temperatures. According to the invention, the corresponding starting compounds II are reacted with sulfur and dimethylammonium dimethylcarbamate III without solvent at reflux temperature, which is 60 to 70 ° C. The result is the compounds of general formula I, as a by-product carbon dioxide escapes, which can serve as a protective gas at the same time (equation 1). The reaction is carried out as follows. that starting compound II, sulfur and the liquid Dimethylammoniumdimethylcarbamat III in a small amount; shot and the mixture for 6 to 12 hours at reflux temperature of Dimethylammoniumdimethylcarbamat (60 to 7O ⁰ C) is maintained. The hot mixture is poured into hot ethanol and allowed to crystallize out in the cold, or it is poured onto ice and the N, N-dimethyl thiamide extracted with ether, which is then evaporated. If necessary, it is recrystallised from ethanol or ethanol / water. If the target of the synthesis is the corresponding aralkylcarboxylic acid, the entire batch can be saponified if necessary or in the case of difficultly crystallizing N, N-dimethylthiamides. The data of some products are summarized in the following table.