DE1301311B - Process for the preparation of pyrroles - Google Patents

Description

The preparation of pyrroles from diacetylenes or substituted diacetylenes and ammonia or primary amines in the presence of catalytic amounts of cuprous chloride is known (Chemical Reports, Vol. 98, [1965], p. 98 and German Auslegeschrift 1 189 080). Instead of diacetylene, the methanol adduct 1-methoxy-buten- (1) -in- (3) can be used. To produce the pyrroles, the components are, if appropriate diluted with solvents, heated to 150 to 1800 C with cuprous chloride.

Pyrrole itself can also be produced continuously if one Ammonia and 1-methoxybutenine at 140 to 1600C over cuprous chloride on carrier substances directs. However, the achievable yields are in some cases very low and lie in the reaction of 1-methoxy-butene (1) 4n- (3) with primary, aromatic amines at 20 to 30%, in the reaction with primary, aliphatic amines, for example the methylamine, even below lO0 / o.

There has now been a method of making pyrroles by reaction of alkanol adducts of diacetylenes with ammonia or primary amines in the presence of a copper (I) -containing catalyst at elevated temperature found that is characterized in that the alkanol adduct of diacetylene with ammonia or primary amines at temperatures from 80 to 2000 C and at pressures from 0.1 to 20 ata is heated in the melt of a cuprochloro-amine complex, whereby a concentration of the starting components in the melt from 2 to 20 percent by weight, based on the weight of the melt, is maintained.

The use of the melt of a cupro-chloroamine complex results better yields and has the advantage that the reaction is easily continuous can be designed. Cupro-chloro-amine complexes arise when exposed to Ammonia or primary amines on cuprochloride or cuprochloro complexes, such as NaCuCl2, NHXCuCl2 or CH3NH3CuCl2, and contain 1 to 3 moles of amine per mole of copper. There are the same amines are useful as in the known processes and are preferred Complexes used which contain the amine intended for the reaction. The melting points such complexes are mostly in the range from 80 to 1500C, which means that the lower temperature limit for carrying out the process is given.

The method is preferably carried out so that the starting components continuously fed to the melt according to consumption and that Reaction product is continuously removed by distillation or extraction.

The alkanol adducts of diacetylene and amine or ammonia can be used in Equimolecular amounts are used. But there can also be one component in excess be applied. So z. B. can be avoided by an excess of amine, that the melt gradually becomes depleted of this component.

The method can be carried out at normal pressure, overpressure or underpressure will. The residence time of highly volatile components can be reduced by using excess pressure be increased in the melt. Underpressure facilitates removal by distillation of the reaction products. When choosing the optimal reaction conditions, the thermal Stability of starting compounds and reaction product to be observed. Useful is a pressure range from 0.1 to 20 ata.

The stationary concentration of the reaction components in the melt should be kept low in the continuous mode of operation and about a maximum 20%, but preferably at least 2%, of the weight of the melt.

While volatile reaction products in particularly simple Way by distillation utilizing the heat of reaction from the reaction zone Can be removed, can be difficult to volatile reaction products by continuous Separate extraction. For this purpose, solvents are used that are under the reaction conditions are non-volatile and immiscible with the melt. Suitable are e.g. B. higher Ether, aromatic and aliphatic hydrocarbons. For extraction can a working method with circulating melt can be used in which the melt from the reactor into the extractor and back again. But it is also possible Carry out the reaction and extraction in an appropriately designed vessel, if the extractant and the extract are supplied with the starting materials is continuously discharged. For the design of the extractor or the combined Reactor extractors can be used to carry out liquid-liquid extractions known construction principles are used.

The extraction of the melt is also suitable for the removal of low-volatility By-products and resins.

Suitable alkanol adducts of diacetylene are, for. B. those with primary, secondary or tertiary aliphatic or cycloaliphatic alcohols of the general Formula R-O-CH = CH-CCH, like 1-methoxy-buten-(1) -yne- (3).

The compounds that can be produced after the implementation according to the method serve as intermediate products for organic syntheses and the manufacture of pharmaceuticals and specialty chemicals. N-methylpyrrole is used as an antioxidant, as an inhibitor for condensation reactions in chlorinated solvents and as a stabilizer for Glycol dieters used.

The production of the cupro-chloro-amine complex takes place, for example as follows: In 100 g of dry cuprous chloride, a strong cup becomes strong until saturation Introduced methylamine stream, the entire mass liquefied with heating. After solidification, the complex is kept under protective gas (N) until it is used. kept.

Example 1 In a vertical glass tube of 20 cm length and 2.5 cm clear width, which is filled with glass balls up to a height of 15 cm, 50 g of cupro-chloro-methylamine complex are filled and placed in a methylamine atmosphere melted. Then 45 g of a 500 / above solution of Methoxybutenine in methanol and 31 g of methylamine at the lower end of the reaction tube fed. That formed by cooling the vapors leaving the reaction tube Condensate hardly contains any methoxybutenine or diacetylene and gives 76010 der Theory of N-methylpyrrole. The N-methylpyrrole has a boiling point of 1150C.

Comparative Example 1 2 g of methoxybutenine, 1.1 g of methylamine and 1 g Cuprous chloride together with 40 ml of methanol for 1 hour in a sealed tube at 1500 C shaken. In the resulting black-brown solution can with the spruce chip reaction no N-methylpyrrole can be detected. The cuprous chloride is in an infusible, chocolate brown mass passed over.

Comparative Example 2 For the implementation of 1-methoxy-buten- (1) -yne- (3) with methylamine in the gas phase, a 50 cm long glass tube is used. The first Half of the tube is coated with potsherds (about 5 mm in diameter) for preheating, while the subsequent reaction zone with pottery shards on which 17.5 g CuCl / 100 g straps are depressed, filled. Through an oil flowing through it surrounding the pipe The temperature is regulated by the jacket.

The tube filling is first at 1500 C in a stream of nitrogen and then Heated for 15 minutes in a stream of nitrogen and methylamine (volume ratio 1: 1) and then in the course of 1 hour at 1500 C 1/4 mol of 1-methoxy-buten- (1) -in- (3), mixed with 29 g of benzene, as well as 1/4 mole of methylamine and 1/4 mole of nitrogen in the preheating zone introduced. The reaction product condensed at the end of the tube becomes N-methylpyrrole determined by proton resonance and gas chromatographic analysis. The conversion is 96.50 / 0, the yield 9% of theory, based on the 1-methoxy-buten- (1) -yn- (3) used.

During the experiment, there was a black color on the catalyst Resin layer deposited.

A reaction with silica gel (grain diameter 3 to 5 mm) as a carrier material for the CuCl. With a methanolic solution, the 50 percent by weight of 1-methoxy-butene (1) - in (3) contains as the starting product all other things being equal, with a conversion of 80 oils, a yield of 0.30 / 0 N-methylpyrrole based on 1-methoxy-buten- (1) -yne- (3) obtained.

Example 2 In a melt of 50 g (0.5 mol) CuCl and 50 ml n-butylamine becomes in the course of 30 minutes at 1700 C and 47 Torr with vigorous stirring Mixture of 50 ml (0.5 mol) of n-butylamine and 90 ml of a methanolic solution, which contains 50 percent by weight of 1-medioxy-buten- (1) -in- (3), initiated. The reaction product distilled from the melt during the reaction and is in a downstream Condenser condenses.

The gas chromatographic analysis shows that there is a conversion of 770/0 N-n-butylpyrrole with a yield of 79 0 / o of theory, based on 1-methoxy-buten- (1) -yne- (3). Used to characterize the product the proton resonance spectrum.

Claims (1)

Claim: Process for the production of pyrroles by reaction of alkanol adducts of diacetylenes with ammonia or primary amines in the presence a copper (I) -containing catalyst at elevated temperatures, d a d u r c h characterized that the alkanol adduct of diacetylenes with ammonia or primary Amines at temperatures from 80 to 2000 C and at pressures from 0.1 to 20 ata in the melt of a cupro-chloro-amine complex is heated, whereby the concentration of the starting components in the melt from 2 to 20 percent by weight, based on the weight of the melt, is maintained.