DE944251C - Process for the preparation of compounds of the pyridine series - Google Patents

Description

Process for the preparation of compounds of the pyridine series Es has been found that compounds of the pyridine series are obtained in good yield if one Glutaraldehyde as such or in the form of their acetals, especially in the form of cyclic enol acetals, d. H. the 2 allcoxy-3, 4-dihydro-i, 2-pyrans, or the corresponding 2-Acyloxy-3, 4-dihydroi, 2-pyrans at elevated temperature in the presence of oxidizing agents with aqueous solutions of ammonium salts.

The implementation proceeds z. B. according to the following scheme: respectively where R "denotes an -alkyl or acyl group, and X -a monovalent anion or the monovalent equivalent of a polyvalent anion.

You can z. B. Use ammonium sulfate or other ammonium salts.

Suitable oxidizing agents are, in particular, salts of higher metals Significance level, which can be reduced to such a lower level, z. B. salts of trivalent iron or manganese, copper (II) salts; also hydrogen peroxide in the presence of iron or copper salts. It is particularly advantageous to use for the implementation z. B. _ Ferriammonium sulfate, which is used both as an ammonium salt and as Oxidizing agent works.

The reaction can be carried out in such a way that the reaction components heated together in aqueous solution, e.g. B. brings to the boil at the reflux condenser. But it is also better to proceed in such a way that the glutaraldehyde or the dihydropyran derivative is used in a heated, e.g. B. boiling solution of the ammonium salt and the oxidizing agent can flow in. The process can also be carried out under increased pressure and / or continuously are executed.

The parts mentioned in the examples are parts by weight.

Example i.

An aqueous-acidic solution of, 14 parts of ß-methyl-glutaraldehyde, by hydrolyzing 128 parts of 2-methoxy-4-methyl 3,4 dihydro-i, 2-pyran with 500 parts of 2% sulfuric acid was obtained gradually into a boiling solution of 964 parts of crystallized ferric ammonium sulfate run in 100 parts of water. After the methanol has been distilled off, the reaction mixture is made alkaline and distilled then the resulting y-picoline is removed. The yield is 85 parts = 91% of theory. The ferric ammonium sulfate solution is added to the solution at ordinary temperature of the ß-methylglutaraldehyde and then heated the mixture for 2 hours on the reflux condenser to boiling, 62 parts of y-Picohn are obtained with otherwise identical work-up.

Example 2 A solution of zoo parts of glutaraldehyde in 800 parts of 3% sulfuric acid in the course of 2 hours in a boiling solution of 100 parts of crystallized ferric sulphate and zoo parts of ammonium sulphate in 1500 Pour in parts of water. When working up according to Example i, pure ones are obtained Pvridine in a yield of 82% of theory.

Example 3 142 parts of 2-ethoxy-5-methyl-3, 4-dihydroi, 2-pyran, which was produced from a-methacrolein and vinyl ethyl ether by diene synthesis, in the course of 2 hours in a boiling solution of x32 parts of ammonium sulfate and 500 parts of crystallized copper sulphate in 100 parts of 100% sulfuric acid a. Working up gives 45 parts of pure β-picoline.

Claims (1)

PATENT CLAIM: Process for the preparation of compounds of the pyridine series, characterized in that glutaraldehyde as such or in the form of their acetates, especially in the form of the cyclic enol acetals, ie the 2-alkoxy-3, 4-dihydroi, 2-pyrans, or the corresponding Reacts 2 acyloxy-3, 4-ffihYdro-i, 2 pyraue at higher temperatures in the presence of oxidizing agents with aqueous solutions of ammonium salts.