IE47783B1

IE47783B1 - Process for the electrochemical preparation of 2-(2-aminoethyl)thiophene

Info

Publication number: IE47783B1
Application number: IE112/79A
Authority: IE
Original assignee: Sanofi Sa
Priority date: 1978-01-25
Filing date: 1979-01-30
Publication date: 1984-06-13
Also published as: BE873677A; EP0003446A1; NO151715B; GR65325B; FI790121A; NO151715C; DK151904C; PT69105A; ES476659A1; MX5460E; EP0003446B1; DK13879A; FR2415671B1; FR2415671A1; DE2960070D1; IT7947735A0; FI62684B; GB2013196B; NO790231L; ATA38379A

Abstract

A process for the preparation of 2- amino-2-ethyl-thiophene, comprises electrochemically reducing 2-nitro-2- vinyl-thiophene, within an organic or aqueous-organic medium, in the presence of an electrolyte, at an acidic pH and at a temperature of 5-40 DEG C, and recovering the desired product from the reaction medium.

Description

This invention relates to a process for the electrochemical preparation of 2-(2-aminoethyl)thiophene. 2-(2-Aminoethyl)thiophene is an intermediate product used in the synthesis of thienopyridine derivatives which have, particularly, blood-platelet aggregation inhibiting, anti-inflammatory and vasodilator activities and which are illustrated in French Patent 2,215,948 and its first certificate of addition 2,345,150.

Thus, this invention relates to a process for the preparation of 2-(2-aminoethyl)thiophene, comprising electrochemically reducing 2-(2-nitrovinyl)thiophene, in an organic or aqueous-organic medium in the presence of an electrolyte, at an acidic pH and a temperature of 5-4O°C and at a potential of 1.10-1.30 V measured with respect to a saturated calomel reference electrode, and recovering the desired product from the reaction medium. Recovery of the product is advantageously effected by means of an organic solvent, after neutralization of the electrolyte.

The organic medium should be such as to permit the solubilization of the starting material, i.e., 2-(2-nitrovinyl)thiophene, and may be, for example, acetic acid, dioxan or methanol.

According to a preferred embodiment of this invention use is made of an aqueous-alcoholic medium comprising 2025 70wt% organic solvent and, preferably, a mixture comprising 50% organic solvent, such as a water-acetic acid (50:50) mixture.

The electrochemical reduction is preferably effected at a potential of about 1.15V.

The pH of the reaction medium should be acidic, and preferably at a value of about 2. Said pH may be obtained by addition of a strong mineral acid such as hydrochloric acid or by means of a suitable buffer (oitrate-HCl, for example).

The electrolyte is added to the organic or aqueousorganic medium to effect the electrochemical reaction and is typically an alkali metal chloride such as sodium or lithium chloride, at a suitable concentration which may be typically 0.2-0.7 mole/1, and preferably 0.5 mole/1.

The temperature of the reaction medium is between 5°C and 40°C, and it is preferred to use room temperature.

The concentration of 2-(2-nitrovinvl)thiophene in the reaction medium is advantageously between 1 g/1 and 10 g/1, and preferably between 1 g/1 and 3 g/1.

As working electrode for the electrochemical cell, a material having a high hydrogen overvoltage , such as mercury, zinc or lead is used, a mercury layer being preferred.

Other features of this invention will appear in the following disclosure, made with reference to the single figure of the accompanying drawing which is given solely for illustrative purposes.

The electrochemical reduction of 2-(2-nitrovinyl)thiophene may be effected in a cell such os that illustrated in the drawing.

Said Cell 1 is divided into an electrolysis compartment 2 and an anodic compartment 3 which are separated by a porous wall 4, of sintered glass, for example, to insure electrical conduction. A platinum or graphite electrode 5 serves as an anode, while electrode 6 (or working electrode) is arranged at the bottom or clbse to the bottom of the electrolysis compartment. Cell 1 is provided, in its compartment 2, with a stirring device for the reaction medium which, in the embodiment illustrated, is a magnet bar 7 arranged in the vicinity of the bottom of the cell.

The cell is also provided with an inert gas inlet 8 fe'slow the level of the electrolyte solution, and with an outlet 9 for said gas in the lid 10 of the cell.

A reference electrode li is placed outside the cell to prevent contamination with the reduction products, the electrical connection being through a bridge 12 comprising a three-way valve 13 and a tube 14 closed wifch sintered glass dipping into cathodic compartment 2.

The following non-limiting Example is given to illustrate the invention.

EXAMPLE The electrochemical reduction of 2-(2-nitrovinyl)thiophene is effected in a cell containing a platinum anode, and the working electrode or cathode which is a mercury layer.

The reaction medium is an acetic acid-water (50:50) mixture and 0.5 molar lithium chloride is used as electrolyte.

The reduction potential is maintained at 1.150 V with respect to a saturated calomel electrode, and the reaction is effected at room temperature.

The 2-(2-nitrovinyl)thiophene is added to the aqueousorganic medium at an initial concentration of 2.5 g/1.

' The cell is maintained under a nitrogen atmosphere and reduction is then effected, with stirring, by passing the current at the predetermined voltage.

On completion of the electrolysis (after passage of 2500 coulombs), the electrolyte of the cathodic compart30 ment is neutralized, extracted with chloroform, and is then washed with water and dried over anhydrous K^CO^. The desired amine is recovered as the hydrochloride or the oxalate 'in ethanol.

The yield of 2-(2-aminoethyl)thiophene is 475 on the basis of the starting material. This yield corresponds also to the faradlc yield, since the amount of electricity passed is that which corresponds to a 100 $ transformation.

Claims

1. CLAIMS:1. A process for the preparation of

2. -(2-aminoethyl)thiophene, comprising electrochemically reducing 2-(2-nitrovinyl)thiophene in an organic or aqueous-organic medium in

3. A process as claimed in claim 1 or 2, wherein the 15 organic or aqueous-organic medium is selected from acetic acid, methanol, dioxan or mixtures thereof with water, the organic medium being present in an amount of 2C—70 wt.%.

4. A process as claimed in claim 3 wherein a wateracetic acid (50:50) mixture is used as medium. 20 5. A process as claimed in claim 1 wherein the reduction is effected at a potential of about 1.15V.

5. 11. A process as claimed in claim 1, wherein the initial concentration of 2-(2-nitrovinyl)thiophene in the reaction medium is 1-10 g/litre. 12. A process as claimed in claim 1 substantially as described herein in the Example. 5 the presence of an electrolyte, at an acidic pH and a temperature between 5°C and 40°C and at a potential of 1.10-1.30 V as measured with respect to a saturated calomel reference electrode, and recovering the desired product from the reaction medium. 10 2. A process as claimed in claim 1, wherein the 2-(2-amino ethyl)thiophene is recovered from the reaction medium by means of an organic solvent, after neutralisation of the electrolyte.

6. A process as claimed in claim 1, wherein the electrolyte is an alkali metal chloride present at a concentration of 0.2—0.7 mole/1. 25

7. A process as claimed in claim 6, wherein said concentration is 0.5 mole/1.

8. A process as claimed in any one of the preceding claims, wherein a mercury, zinc or lead cathode and a platinum or graphite anode are used as electrodes.

9. A process as claimed in any one of the preceding claims, wherein the extraction solvent is chloroform. 10. A process as claimed in claim 1, wherein the reaction temperature is room temperature.

10. 13. Thienopyridine derivatives when prepared from 2-(2-amino ethyl)thiophene prepared by a process as claimed in any one of the preceding claims.