DE1695261C3 - Process for the preparation of N, N "disubstituted bipyridylium salts - Google Patents

Description

The invention relates to the manufacture of

N.N'-disubstituted 4,4'-bipyridy humus salts.

The subject of patent 1 545 991 is a process for the preparation of Ν, Ν'-disubstituted 4,4'-bipyridylium salts, which is characterized in that a Ν, Ν'-disubstituted tetrahydro-4,4'-bipyridyl is treated with an oxidizing agent consisting of an organic compound which is a Is hydrogen acceptor and has a redox potential that is more positive than - 1.48 V. The redox potential is related to the standard calomel electrode. According to claim 2 of this patent, as an oxidizing agent Quinones used.

It has now been found that N, N'-disubstituted tetrahydro-4,4'-bipyridyls are advantageous Can be converted into the corresponding bipyridylium salts if one is specifically called quinones substituted anthraquinones used, which can be regenerated by oxygen.

Accordingly, the invention relates to a process for the preparation of Ν, Ν'-disubstituted 4,4'-bipyridylium salts according to patent 1,545,991, which is characterized in that an oxidizing agent is used 9.10-anthraquinone substituted by 1 or 2 chlorine atoms is used.

The substituted 9,10-anthraquinone preferably has no substituents on its "! carbon atoms, since it has been found that such substituents generally slow down the rate of reaction, presumably through steric Prevention of the 9 and / or 10 position. It was found, that the oxidizing agent which can be used according to the invention is 1-chlorine, 10-anthraquinone. 1,5-dichloro-9,10-anthraquinone, 1,8-dichloro-9,10-anthraquinone, 2,6-dichloro-9, IO-anthraquinone and in particular 2-chloro-9.10-anthraquinone are suitable.

The Ν, Ν'-disubstituted tetrahydro-4,4-bipyridyls "can in particular N, N'-D» a ky -tetrahydro-44'-bipyridyl or N.N'-dicarbamylalkyl-tetrahydro-4V-bipyrid> le as described in more detail in Belgian patent specification 662 281.

The reaction can conveniently be carried out in an inert solvent, both the N N'-disubstituted tetrahydro-4,4-bipyndyl as also dissolves the substituted 9,10-antbrachinone. Substituted 9,10-anthraquinones are not always readily soluble in organic solvents, however it has generally been found that suitable solvents are selected from the following groups can · ether, such as B. diethyl ether, tetrahydrofuran Bis- {2-methoxyethyl) ether and dibutyl ether of diethylene glycol; Ketones such as B. acetone and Mcthyläthylketon; Hydrocarbons such as B. benzene and alkylbenzenes; inert halogenated hydrocarbons, especially chlorinated hydrocarbons, such as B. methylene chloride, and Geraische from such solvents. If so desired. the To carry out the reaction in solution, then the choice of a suitable substituted 9,10-anthraquinone by "the" solubility of the available substituted 9,10-anthraquinone can be determined in the available solvent.

The speed of reaction depends on each used substituted 9,10-anthraquinone ah. Hs it was found that in general those 9.10-Λη-thrachinones, the substituents on the alpha carbon atoms have, react more slowly than correspondingly substituted 9,10-anthraquinones. in which these positions are not substituted. It has been found that times as short as 0.5 hour for reactions with substituted 9,10-anthraquinones. in which the aipha gradients are not substituted and that times of up to 20 hours are necessary for alpha-substituted 9,10-anthraquinones could be.

The reaction takes place at temperatures from 0 to 7 ° C and in particular at temperatures from 30 to 60 ° C accomplished.

Appropriate ratios are usually at least 2MoI "substituted 9.10-anthraquinone per mole Ν, Ν'-disubstituted tetrahydro-4,4'-bipyrid \ l. although smaller proportions may also be used can be. It has generally been found that the rate of reaction with a increased proportion of substituted 9,10-anthraquinone

increases.

The reaction product presumably contains the N.N'-disubstituted 4,4'-bipyridylium salt of the reduced or partially reduced substituted 9'0-anthraquinone, such as / .. B. a salt of the formula

CH ₃ -N

N-CH ₃

OH

which can be converted into the usual bipyridylium salt and into free substituted 9,10-anthraquinol

i 695

can, by treatment with an acid that is stronger than the substituted 9,10-anthraehinol, especially with a mineral acid, such as. B. Salarians, Sulfuric acid or phosphoric acid.

The bipyridylium salt and the substituted 9,10-anthraquinone, thus set free can be separated and won by conventional means] will. For example, the substituted 9,10-anthraquinol can be derived from the bipyridylium alkylate by distribution between water (which is preferably the bipyridylium salt and any quaternary salts that are passed through Cleavage of the N.N'-disubstituted tetrahydro-4,4'-bipyridyl are obtained, retains) and a water-immiscible solvent, v / ie z. B. a Ether (which preferably dissolves the substituted 9,10-anisoquinol). Possibly the substituted 9,10-anthraquinol can then be removed from the solvent phase by simple evaporation be separated.

The substituted 9,10-Anthrachincl can be converted into the corresponding substituted 9,10-anthraquinone, by the 9,10-Anihrachinol isolated as a solid and then preferably dissolved in a finely divided form, with i-INEM oxygen-containing gas in contact ^1! eight is, for example, this is passed through or over a bed of solid substituted 9,10-anthraquinol. Alternatively and preferably, a solution containing the substituted 9.10-Aiilhraquinol, directly with an oxygen-containing gas, such as. B. air, are treated in order to oxidize the substituted 9.10-anirachinol to the corresponding anthraquinone. However, if a highly flammable solvent such as diethyl ether is used, dangerous explosive mixtures can result form solvent vapor from the oxygen-containing gas, and care should therefore be taken in the selection of the solvent and in the selection of the reaction conditions in order to avoid the formation of such explosive mixtures. The oxygen-containing gas can be mixed with the solution according to any conventional Procedure for bringing liquids and gases into contact, e.g. by blowing the gas through the solution,

It is preferred to use oxygen for the conversion of the substituted 9,10-anthraquinol to the corresponding 9,10-anthracbinone, although other oxidizing agents such as e.g. B. chlorine can optionally also be used.

The oxidation of the substituted 9,10-anthraquinol can conveniently be carried out at room temperatures, but it has been found that increasing the temperature generally increases the rate of the reaction and it is therefore preferred to carry out the oxidation at a temperature as high as that the boiling point of the solvent is compatible, provided the oxidation is carried out in a solvent, or at a temperature slightly below the decomposition temperature of the anthraquinol. provided that the oxidation is carried out in the solid state.

The acidic aqueous phase containing the bipyridylium salt contains, usually also contains some N-substituted pyridinium salts, which are formed by a side reaction in which cleavage of the N, N'-disubstituted Tetrahydro-4,4'-bipyridyls occurs, and it may be desirable for economic reasons, to separate these N-substituted pyridinium salts from the bipyridylium salts, e.g. B. by the selective execution method c. those in the German U.S. Patent 1,545,991 is described in more detail. N-substituted pyridinium salts obtained in this way were, in N.N-disubstituted tetrahydro-4,4'-bipyridy! e be converted, such as B. by the reduction process, which is in the German U.S. Patent 1,545,991.

The invention is explained in more detail with reference to the following examples. All parts and percentages are expressed in weight.

example

To a solution of 16.6 g (O.O8SM0I1 N.N'-dimethyl-tetrahydro-4,4'-bipyridyl in tetrahydrofuran was slowly added a solution of 0.176 viol 2-chloro-9,10-anthraquinone in 500 ml tetrahydrofuran in a "tetigen current during a period of 15 micro butene was added. the temperature of the Rcak tion solution was maintained at 35 ° C, and the reaction was stirred with stirring under a nitrogen atmosphere.

After one hour, 200 ml of 1M hydrochloric acid (0.20 mol) were added to the reaction mixture. The resulting solution was carried out for a further 5 minutes ; then the solvent is removed under reduced pressure in a rotary evaporator. The aqueous phase was filtered in air and then extracted continuously with 500 ml of diethyl ether in order to remove 2-chloro-9.10-anthraquinone (which had been formed by air oxidation of the 2-chloro-9.10-anthraquinol formed by the reaction). It was found that the aqueous phase after the extraction contained both N-methylpyridinium chloride as well as N.N'-dimethyl-bipyridylium chloride , the latter being determined by colorimetric analysis of the colored product from the reaction of the bipyridylium ion with sodium dithionite . The yield of bipyridylium salt was 75%, based on consumed N.N'-methyltetrahydro - ^ '- bipyridyl.

example The procedure of Example 1 was followed using Substitute 60. The yield of bipyridylium

of 2-chloro-9,10-anthraquinone by 0.176MoI salt was 71%, based on N, N'-di-

l-chloro-9,10-anthraquinone repeated, the methyltetrahydro ^ '- bipyridyl. Response for 17 hours instead of ! Hour

Example 3

The procedure of Example 1 was repeated, the results compiled in the following table for the use of various oxidizing agents and solutions were obtained, medium, reaction times and reaction temperatures

solvent Line temperature Yield"!
related to
zugeCührle !. Ausbeui Oxidizing agent Tetruhydro (SId-) IC) bi pyridyl Diethyl ether 20th 0 37 37 1 -Chlor-9,10-anthraquinone Tetrahydrofuran 20th 0 69 70 the same Diethyl ether 1 35 19th 19th the same Diethyl ether 17th 35 71 71 the same Tetrahydrofuran 17th 35 55 55 the same Methylene chloride 17th 40 52 55 the same Bis- {2-methoxyethyl) - 17th 35 68 70 the same ether Dibutyl ether of di- 17th 35 67 71 the same ethylene glycol benzene 17th 35 66 68 the same Alkylbenzene mixture 35 69 71 the same acetone IS 35 67 71 the same Methyl ethyl ketone IS 35 61 63 the same Diethyl ether 17th 35 56 64 2-chloro-9,10-anthraquinone Tetrahydrofuran T 35 74 77 the same Methylene chloride -, 40 70 78 the same Alkylbenzene mixture I. 35 68 70 the same Bis (2-methoxyether I. 35 68 71 the same benzene ■) 35 67 69 the same acetone -> 35 70 75 the same Methyl ethyl ketone -) 35 66 72 the same Alkylbenzene mixture 7th 0 12th 12th the same Tetrahydrofuran 1 0 27 28 the same Methylene chloride S. 0 47 50 the same Tetrahydrofuran T 45 50 75 80 the same Tctrahvdrofuran -) 45 50 77 81.5 2-ChIoT-Q. 10-anthraquinone (50% excess) Diethyl ether 20th 35 61 65 1.5-dichloro-9, IO-an- thrachinone Alkyl follows mixed IH 35 ω 64 the same Tetrahydrofuran IS 40 71 the same Tetrahydrofuran IS 40 66 1.8-dichloro-9, IO-an- thrachinone Diethyl ether IS 35 68 the same Alkylbcn / olgcmisch IS 40 62 the same Hcti / ol 4.5 45 50 56 2.6-dichloro-9.10-an- thrachinone acetone 20th 45 50 68 the same

* l Ausheule isl calculated on the basis of de- \ crbi ..lichten 'Ietrah> i.lr < > htp> nd \ U. dinium chloride was bcriieksichiiüt. J.i ^ Ick! ' -n lelr.ihulrobi | i \ ni! v i nm ^ ew.itulel

ttnbci diis u.ihrem] of the reaction fiebildclc Mclh \ lp \ ri ! graze kiln

Claims (1)

i 695 Claim: Process for the preparation of N, N'-disubstituted 4,4'-bipyridylium salts by treatment an N, N'-disubstituted tetrabydro-4,4'-bipyridyl with an oxidizing agent consisting of an organic compound which is a hydrogen acceptor and has a redox potential that is more positive than -1.48 V, according to ι ο Patent 1545991, characterized in that that the oxidizing agent is a 9,10-anthraquinone substituted by 1 or 2 chlorine atoms used. 15th