DE887198C - Process for the preparation of naphthostyrils - Google Patents

Description

Process for the preparation of naphthostyrils The invention relates to a process for the preparation of substituted and unsubstituted naphthostyrils.

Naphthostyrils, which are used as intermediates in the manufacture of Vat dyes are important, e.g. B. those of the anthanthron row, were previously produced only by cumbersome processes, the simplest of which is diazotization of r-aminonaphthalene-8-sulfonic acid, the conversion into the corresponding nitrite and comprises the alkali melt. The yields were low and the previous procedures were able to produce many substituted naphthostyriles as a result of the Inaccessibility of the corresponding aminonaphthalenesulfonic acids are not used.

The invention relates to a new process starting from α-naphthyl isocyanates and α-naphthyl isothiocyanates. These compounds are isomerized by heating with a Friedel-Crafts catalyst with the formation of naphthostyrils or their sulfur analogues. The process for the production of unsubstituted naphthostyril from α-naphthyl isocyanate is illustrated by the following scheme If α-naphthyl isothiocyanate is used, the first step in the process likely involves the formation of the sulfur analog of naphthostyril in which the oxygen is replaced by sulfur. This sulfur compound appears to be converted to the corresponding naphthostyril by treatment with aqueous alkali and acidification. It is not necessary to isolate any intermediate in the pure state; rather, the second process step can be carried out in the same reaction vessel. In any case, the same very pure naphthostyrils are obtained from α-naphthyl isothiocyanates; as from the a-naphthyl isocyanates.

The process is not limited to the production of unsubstituted Naphthostyril applicable, but also to substituted naphthostyrils in which the peri position carries a reactive hydrogen atom. Examples of such Substituents are halogens, e.g. B. chlorine or bromine, nitro groups, oxy groups, alkoxy groups and the like

It is an advantage of the invention that it works in general the Friedel-Crafts reactions can be followed. Typical catalysts, such as aluminum chloride, aluminum bromide, boron trifluoride, zirconium chloride and the like are used will. As a result of its cheapness, easy accessibility and good properties aluminum chloride is the preferred catalyst.

It has been found that dilution is beneficial as when concentration the isocyanate in the reaction mixture becomes too high, like this without using Diluents is the case, there is a tendency to intermolecular conversions which consists of the generation of undesirable by-products.

The selection of the diluent again can be as in Friedel-Crafts syntheses take place, and the usual anhydrous diluents, which in such reactions are also applicable here. These include solid substances, such as Sodium chloride and the like, inert organic liquids, either of the series the negatively substituted aromatics, e.g. B. chlorobenzene, o-dichlorobenzene and the like, or the aliphatic class, such as nitromethane, acetylenetetrachloride, carbon disulfide, high-boiling paraffins and the like.

The nature of the diluent to be used will in some cases influenced by the temperature at which the reaction is carried out. These Temperature is not critical, but slightly elevated temperatures will result in higher temperatures Yields and better products. Without the invention to special temperatures limit, a temperature range between about 100 and 200 ° C is preferable. If the higher temperatures of this preferred range are used, so is the diluent is preferably one that has a fairly high boiling point and this includes a number of low boiling points for most operations Diluents from, e.g. B. carbon tetrachloride or carbon disulfide, which again offer economic advantages in a different way. Of course it's possible, to operate under pressure, and such methods are within the scope of the invention. However, on the one hand there are increased costs and problems when using autoldaves occur, on the other hand, many inert diluents with rather high Working at atmospheric pressure is preferable. The diluent can be present in excess.

The a-naphthyl isocyanates are normally produced by reacting the corresponding a-naphthylamines prepared with phosgene. It is possible in isolation to use pure isocyanate, but not necessary. It was found that the Reaction mixture of a-naphthylamines with phosgene used for isomerization when the excess phosgene has been removed. It's not necessary, to isolate the a-naphthyl isocyanate from the reaction mixture, and therefore fall such mixtures are within the scope of the invention. The exact constitution of the reaction mixture of phosgene and a-naphthylamines and was not fully determined. , It is not a pure dispersion of isocyanate. There are impurities however, which do not appear to have an adverse effect on isomerization. An impurity, the corresponding carbamyl chloride, that is likely in the Reaction mixture is present is also cychsiert, possibly by first Isocyanate is formed. In any case, a considerable proportion seems to exist Carbamyl chloride to be effectively exploited.

The use of impure reaction mixtures of phosgene and a-naphthylamine, as described above, is advantageously suitable for a combined method that is the reaction with phosgene and the second process step is isomerization be carried out in the same reaction medium. There is an advantage in being the same Diluent used in this modification for both process steps can be. However, it is not necessary that the concentrations be the same. It is thus possible to carry out the first process step in a somewhat more concentrated reaction medium carry out and by adding more diluent the desired more dilute To obtain medium for isomerization.

The present invention will now be made by way of the following examples are explained in more detail. The parts mean amounts by weight.

Example i A solution of 8.5 parts of a-naphthyl isocyanate in 52 parts of o-dichlorobenzene is gradually added to a suspension of 16 parts of aluminum chloride in 130 parts of o-dichlorobenzene, which is kept at 160 °. The mixture is poured into dilute hydrochloric acid and the solvent is removed by steam distillation. The aqueous suspension that remains is filtered and the filter cake is extracted with 330 parts of 2.5 N sodium hydroxide at 85 to 0 °. The yellowish extract is acidified with hydrochloric acid and warmed to go °. The precipitate of naphthostyril is filtered and dried at 20 ° and gives an excellent yield of a product of great purity.

Example e A solution of 8.5 parts of α-naphthyl isocyanate in 52 parts Trichlorobenzene gradually becomes a slurry of 8.0 parts of aluminum chloride in 13o parts of trichlorobenzene, which is kept at x75 °, given. The reaction mixture is worked up as described in the example and gives naphthostyril in good quality Yield and purity.

The same product is obtained by adding 16.9 parts of a-naphthyl isocyanate with stirring to a mixture of 27 parts of sodium chloride and 54.0 parts of aluminum chloride at 15o °. The reaction is ended at 18o to sgo ° and the mixture is poured into water poured. The product is filtered and washed. It can be recrystallized can be purified from toluene.

Example 3 4 parts of 1-amino-4-chloronaphthalene are dissolved in 52 parts of dichlorobenzene and the solution is saturated with dry hydrogen chloride. Phosgene is passed into the slurry at 150 ° until a clear solution is formed. That. Excess phosgene is removed under reduced pressure and the remaining solution is gradually added to a slurry of 6 parts of aluminum chloride in 65 parts of dichlorobenzene, which is kept at 160 °. The reaction mixture is worked up as indicated in Example 1. 4-chloronaphthostyril is obtained in good yield.

Example 4 13 parts of 1-amino-2-methylnaphthalene hydrochloride in 169 parts of o-dichlorobenzene are treated with phosgene at 170 ° until a clear solution is obtained. The mixture is then concentrated under reduced pressure to remove the excess phosgene. The residue is gradually added to a slurry of 19.4 parts of aluminum chloride in 208 parts of dichlorobenzene which is kept at 160 °. The mixture is worked up in the usual way and gives 2-methyl-naphthostyril, a greenish-yellow substance, mp 24 ° (uncorr.). Example 5 A solution of 8.5 parts of α-naphthyl isocyanate in 52 parts of dichlorobenzene is gradually added to a slurry of 8.0 parts of aluminum chloride in 130 parts of dichlorobenzene which is kept at 130 °. The reaction mixture is worked up in the usual way and gives practically pure naphthostyril. Example 6 35 parts of zirconium tetrachloride are stirred into 130 parts of o-dichlorobenzene. 8.5 parts of α-naphthyl isocyanate in 52 parts of dichlorobenzene are added to the rapidly stirred slurry, which is kept at about 75.degree. The naphthostyril is isolated from the reaction mixture in a customary manner. Example 7 2.3 parts of 1-amino-5-methoxynaphthalene hydrochloride in 32 parts of o-dichlorobenzene are treated with phosgene at 130 ° until a clear solution is obtained. The excess phosgene and a little dichlorobenzene are removed under reduced pressure. The residue is gradually added to 20 parts of zirconium tetrachloride in 52 parts of dichlorobenzene, which are kept at 14o °. After the dichlorobenzene has been removed by steam distillation, the residue is extracted with 2.5 molar sodium hydroxide solution and the crude product is precipitated with acid and heated to form the lactam. The dried substance is extracted with hot toluene, the brownish yellow crystals of 5-methoxy-naphthostyril settle out. Example 8 A mixture of 4 parts of aluminum chloride and 65 parts of o-dichlorobenzene is heated to 50 ° and 1.6 parts of a-naphthyl isothiocyanate are gradually added. After the addition is complete, the mixture is stirred at the same temperature until the reaction stops. The reaction mixture is then poured into 25 parts of 5N hydrochloric acid and the dichlorobenzene is removed by steam distillation. The mixture is cooled and filtered. The product is dissolved and clarified in sodium hydroxide solution, which contains some alcohol. The solution is heated for a long time and then acidified with hydrochloric acid. The precipitated product is cooled and filtered.

A good yield of naphthostyril is obtained, which if it in even greater purity is desired, continue by loosening can be cleaned in hot caustic soda and acidification.

Claims (6)

PATENT CLAIMS: r. Process for the preparation of naphthostyrils, characterized in that an unsubstituted or substituted α-naphthyl isocyanate or isothiocyanate is reacted with a Friedel-Crafts catalyst, the reaction product is extracted with an alkali and the resulting unsubstituted or substituted naphthostyril is precipitated with an acid. 2. The method according to claim r, characterized characterized in that the reaction in the presence of an inert diluent, z. B. an anhydrous inert organic liquid is carried out. 3. Method according to claim 2, characterized in that; that the diluent itself with respect to the amount of isocyanate or isothiocyanate is in excess. q .. procedure according to one of the preceding claims, characterized in that the implementation is carried out at a temperature in the range of about roo to 200 °. 5. Method according to one of the preceding claims, characterized in that as Friedel-Crafts catalyst aluminum chloride is used. 6. Procedure after a of the preceding claims, characterized in that the isocyanate or isothiocyanate generated in situ from the corresponding a-naphthylamines and phosgene or thiophosgene will.