GB2178427A

GB2178427A - Preparation of N-alkyl- and N-arylsulfonyloxynaphthalimides

Info

Publication number: GB2178427A
Application number: GB08616245A
Authority: GB
Inventors: Hansrudolf Schwander
Original assignee: Ciba Geigy AG
Current assignee: Novartis AG
Priority date: 1985-07-11
Filing date: 1986-07-03
Publication date: 1987-02-11
Also published as: JPS6219571A; BE905085A; DE3524808A1; CH667088A5; GB8616245D0

Abstract

A process for the preparation of N-alkyl- and N-arylsulfonyloxy-naphthalimides of the formula <IMAGE> wherein R is an alkylsulfonyl or arylsulfonyl radical and R' and R'' are each independently of the other hydrogen, alkyl, alkoxy, halogen, N,N-dialkylamino or nitro, starting from the appropriate naphthalic anhydride, comprises converting a naphthalic anhydride with hydroxylamine or a hydroxylammonium salt, using water as reaction medium, into the hydroxynaphthalimide, and reacting this intermediate, without isolation, with an alkyl or aryl sulfochloride to give the N-alkyl, or N-arylsulfonyloxynaphthalimide. The process is simple to perform and requires no organic solvents requiring regeneration after working up. N-alkyl- and N-arylsulfonyloxynaphthalimides are important dyestuff intermediates which, after they have been reacted to the corresponding naphtholactams, are used e.g. for the synthesis of naphthostyryl dyes.

Description

SPECIFICATION Process for the preparation of N-alkyl- and/or N-arylsulfonyloxynaphthalimides The present invention relates to a process for the preparation of N-alkyl- and/or N-arylsulfonyloxynaphthalimides starting from naphthalic anhydride.

N-Alkyl- and N-arylsulfonyloxynaphthalimides are important dyestuff intermediates which, after they have been converted into the corresponding naphtholactams (q.v. U.L. Plakidin et al., J. Org. Chem USSR 10 (1974), Part 2, page 2249), are used for the synthesis of naphthostyryl dyes. Such dyes and the preparation thereof are disclosed e.g. in German Auslegeschrift 1 917454.

A method of preparing 1,8-naphtholactam (naphthostyryl) that has long been known comprises starting from naphthalimide, obtained by heating naphthalic an hydroxide with aqueous ammonia (Ullmann, 4th Edition, Vol. 9 (1975), page 153) and converted by Hofmann degradation into naphthostyryl [F. Ullmann et al., Chem. Ber. 43, 439 (1910)]. The drawback of this method is, however, that the desired product is only obtained in low yield.

A process for the preparation of N-alkyl- and N-arylsulfonyloxynaphthalimides, likewise starting from naphthalic anhydride, is also known. In this process, naphthalic anhydride is reacted in a first step with hydroxylamine to give N-hydroxynaphthalimide, the N-hydroxy group of which is subsequently acylated with a sulfochloride, e.g. benzene sulfochloride (q.v. German Offenlegungsschrift 2 417 789). The reaction of naphthalic anhydride with hydroxylamine is conducted in a protic solvent such as water or propionic acid, whereas the subsequent acylation is carried out in an organic solvent such as methanol or pyridine. This process is rather complicated and laborious, as the reaction of the acid anhydride with the hydroxylamine and the subsequent acylation are carried out in different solvents and the hydroxynaphthalimide obtained as intermediate is isolated.

At the present time, efforts are being increasingly directed to simplifying substantially the synthesis carried out on an industrial scale for obtaining intermediates in order to achieve as efficient and economic a mode of operation as possible by eliminating process steps. In the course of seeking to develop a simple process for the preparation of N-alkyl- and N-arylsulfonyloxynaphthalimides, it has been found that naphthalic anhydride can be reacted direct in succession with hydroxylamine or a hydroxylammonium salt and a sulfochloride, using water as reaction medium and without isolating the hydroxynaphthalimide obtained as intermediate, to give the desired final product by means of a single vessel process.

In view of the fact that the reaction is carried out in suspension (educt and product are virtually insoluble in water), the reaction proceeds surprisingly uniformly in good yield and without any appreciable hydrolysis of the sulfochloride formed by using water as reaction medium. A further advantage is that the use of water as reaction medium avoids the problem of solvent regeneration.

Accordingly, the present invention relates to a process for the preparation of N-alkyl- and N-arylsulfonyloxynaphthalimides of the formula

wherein R is an alkylsulfonyl or arylsulfonyl radical and R' and R" are each independently of the other hydrogen, alkyl, alkoxy, halogen, N,N-dialkylamino or nitro, starting from the appropriate naphthalic anhydride, which process comprises converting a naphthalic anhydride with hydroxylamine or a hydroxylammonium salt, using water as reaction medium, into the hydroxynaphthalimide, and reacting this intermediate, without isolation, with an alkyl or aryl sulfochloride to give the N-alkyl- or N-arylsulfonyloxynaphthalimide.

The reaction proceeds in accordance with the following equation, as exemplified by the reaction of naphthalic anhydride with hydroxylamine sulfate and benzene sulfochloride to give the N-phenylsulfonyloxynaphthalimide.

hydroxynapbthalimide In addition to naphthalic anhydride, a substituted anhydride may also be used as starting material. The radicals R' and R" referred to above are preferably hydrogen, but may also be alkyl, preferably lower C,-C4alkyl such as methyl, ethyl, propyl, butyl or also isopropyl or sec-butyl; and also alkoxy, preferably lower Ca-C4 alkoxy such as methoxy, ethoxy, propoxy, butoxy or also isopropoxy or tert-butoxy, with further suitable contenders being halogen such as fluoro, chloro or bromo, or also the nitro or N,N-dialkylamino group, e.g. the N,Ndimethylamino group.

The naphthalic an hydroxide or suitable derivative is reacted in a first step with hydroxylamine, preferably in the form of an aqueous solution, or with a hydroxylamine salt. A suitable hydroxylamine salt is e.g. hydroxylamine chloride, sulfate or nitrate, with hydroxylamine sulfate being preferred.

The hydroxynaphthalimide obtained as intermediate is acylated with alkyl or aryl sulfochloride of the formula R-SO2CI. The radical R is alkyl, preferably lower C,-C4alkyl such as methyl, ethyl, n-propyl, n-butyl, isobutyl, sec-butyl or tert-butyl. Alkyl shall also be understood as meaning a phenyl-substituted alkyl radical such as benzyl or phenylethyl. In addition, R is aryl, in particular phenyl which may be unsubstituted or substituted by e.g. methyl, ethyl, chloro, bromo or the nitro group.Examples of such sulfo-chlorides are 2-methylbenzene sulfochloride, 3-methylbenzene sulfochloride, 4-methylbenzene sulfochloride, 2,3-dimethylbenzene sulfochloride, 3,4-dimethylbenzene sulfochloride, 2,6-dimethylbenzene sulfochloride, 3,5-dimethylbenzene sulfochloride, 2-ethylbenzene sulfochloride, 3-ethylbenzene sulfochloride, 4-ethylbenzene sulfochloride, 2,3diethylbenzene sulfochloride, 3,4-diethylbenzene sulfochloride, 2,6-diethylbenzene sulfochloride, 3,5-diethylbenzene sulfochloride, 2-nitrobenzene sulfochloride, 3-nitrobenzene sulfochloride and 4-nitrobenzene sulfochloride. The preferred acylating agent in the process of this invention is benzene sulfochloride.

The reaction of the unsubstituted or substituted naphthalic an hydroxide with hydroxylamine or the hydroxylammonium salt is conveniently carried out in the temperature range from 1 0 C to the boiling point of the reaction mixture, preferably in the range from 60 to 1 00 C, and at a pH value close to the neutral point, preferably at pH 6.5 to 7.5.

The acylation of the hydroxynaphthalimide is conveniently carried out in the temperature range from 10 to 50"C and at a pH in the range from 8 to 13.5.

The pH value for the reaction with hydroxylamine or the hydroxylammonium salt as well as for the subsequent acylation is normally adjusted with a hydroxide or carbonate of an alkali metal or alkaline earth metal in the form of an aqueous solution or suspension, or with a tertiary amine such as triethylamine or piperidine. It is preferred to adjust the pH value with an aqueous solution of sodium hydroxide.

Depending on the temperature and the size of the batch, the reaction time is from about 3 to 10 hours.

Working up - and this is a a further advantage of the process described herein - is extremely simple, as the product is virtually insoluble in the reaction medium and can be readily isolated by filtration, centrifugation or decantation. The product is then preferably washed with water and dried. The N-alkyl- or N-arylsulfonyloxynaphthalimides so obtained can be further processed direct to give the corresponding naphtholactams.

It is not necessary to purify the products beforehand.

The process of this invention is carried out, for example, as follows: Naphthalic anhydride is suspended in water (about 1 mole of anhydride in preferably about 1 litre of water) and then an approximately equimolar amount of hydroxylammonium salt, e.g. hydroxylamine sulfate, is added to the suspension. it is best to add a small excess of hydroxylammonium salt, preferably a 10% excess, based on the equimolar amount. The reaction mixture is then heated to about 90"C and the pH is adjusted to about 6.5 - 7.5 with sodium hydroxide solution. After a reaction time of about 1 to 3 hours, the reaction mixture is cooled to room temperature and the pH is increased to > 10, preferably to about 13, by adding sodium hydroxide solution.

Then the sulfochloride, e.g. benzene sulfochloride, is added, likewise preferably in 10% excess, based on the equimolar amount. With increasing acylation the pH of the reaction mixture falls below 10 to about pH 9. The reaction is complete after about 2 to 5 hours and the product is isolated by filtration. The O-acyl hydroxynaphthalimide is then washed with water and dried. The yield obtained in this process is generally over 90%. The invention is illustrated by the following Example, in which parts and percentages are by weight.

Example: 99.1 parts of naphthalic an hydroxide are suspended in 500 parts of water and to the suspension are added 45.1 parts of hydroxylamine sulfate. The suspension is heated to 90"C and the pH is adjusted to 6.5-7.5 by the dropwise addition of about 60 parts of a 50% solution of sodium hydroxide. After it has been stirred for 1 hour at 90to, the reaction mixture is cooled to 25"C and the pH is adjusted to c.1 3 by the dropwise addition of about 44 parts of a 50% solution of sodium hydroxide. Then 98 parts of benzene sulfochloride are added dropwise at room temperature over 1 hour. The pH value falls during the acylation and is about 9 after another hour. The reaction is at this time almost complete. The product is isolated by filtration, washed with water and dried, affording 163 parts of N-phenylsulfonyloxynaphthalimide, corresponding to a yield of 92%. The product has a melting point of 206"C.

Claims

1. A process for the preparation of an N-alkyl- or N-arylsulfonyloxynaphthalimide of the formula

2. A process according to claim 1, wherein the reaction of the unsubstituted or substituted naphthalic anhydride with hydroxylamine or the hydroxylammonium salt is carried out in the temperature range from 1 0 C to the boiling point of the reaction mixture and at a pH value close to the neutral point.

3. A process according to claim 2, wherein the reaction is carried out in the temperature range from 60"C to 1 00'C and at a pH value from 6.5 to 7.5.

4. A process according to claim 1, wherein the reaction of the hydroxynaphthalimide with the alkyl and aryl sulfochloride is carried out in the temperature range from 10 to 50"C and at a pH value from 8 to 13.5.

5. A process according to any one of claims 1 to 4, which comprises reacting naphthalic anydride with hydroxylamine sulfate and subsequently reacting the hydroxynaphthalimide obtained as intermediate with benzene sulfochloride to give N-phenylsulfonyloxynaphthalimide.

6. An N-alkyl- or N-arylsulfonyloxynaphthalimide obtained by the process as claimed in claim 1.