Preparation of N,N'-dialkylperylene-3,4,9,10-tetracarboxylic aci

Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...

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546 36, C07D47102

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active

060840994

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BRIEF SUMMARY
The present invention relates to a novel process for the preparation of N,N'-di(C.sub.1 -C.sub.4) alkylperylene-3,4,9,10-tetracarboxylic acid diimides (I) by the reaction of perylene-3,4,9,10-tetracarboxylic acid diimide (II) with a C.sub.1 -C.sub.4 alkyl halide.
N,N'-di(C.sub.1 -C.sub.4)alkylperylene-3,4,9,10-tetracarboxylic acid diimides (I q; referred to below as "dialkyl perylimides"), and primarily dimethyl perylimide (Ia q; C.I. Pigment Red 179), represent important pigments for dyeing varnishes, in particular motor vehicle enamels and plastics materials.
Various processes for the preparation of dimethyl perylimide (Ia) are known, these being summarized in DE-A 2,727,484. Thus the preparation of (Ia) can take place by the reaction of perylene-3,4,9,10-tetracarboxylic acid diimide (II; referred to below as "perylimide") with methyl chloride in sodium hydroxide solution under pressure (DE-A 1,272,270), by alkali metal hydroxide fusion of N-methylnaphthalenecarboxylic acid imide (DE-PS 276,357), or by the reaction of perylene-3,4,9,10-tetracarboxylic acid dianhydride with aqueous methylamine under pressure (DE-A 2,153,087). Only in the last-named reaction, which is elaborate, since the dianhydride must first of all be prepared by saponification of perylimide (II), pigments can be obtained in tints ranging from pure red to yellowish red, whilst the first-named reactions give pigments in chestnut tints, which are subjected to elaborate purification steps such as vatting, alkaline extraction of the leuco-compound, and reoxidation (DE-A 2,727,484) to obtain pure red tints.
Furthermore WO-A 96/08537 describes a process for the N-methylation of organic pigments by reaction with dimethyl carbonate in the presence of triethylamine and a polar organic solvent such as dimethyl acetamide. In this reaction, which takes up to 100 h, however, only mixtures of products having different degrees of methylation are obtained, and these must be separated. Thus dimethyl perylimide (Ia) is also obtained only in the form of a chestnut-colored product having a purity of 62%.
It is thus an object of the invention to make dialkyl perylimides (I) economically available in high purity and good yields.
Accordingly, we have found a process for the preparation of N,N'-di(C.sub.1 -C.sub.4)alkylperylene-3,4,9,10-tetracarboxylic acid diimides (I) by the reaction of perylene-3,4,9,10-tetracarboxylic acid diimide (II) with a C.sub.1 -C.sub.4 alkyl halide, wherein the reaction is carried out in a dipolar-aprotic organic solvent in the presence of an inorganic base.
Suitable dipolar-aprotic solvents for this purpose are, in addition to sulfoxides and sulfolanes, primarily carboxamides, in particular aliphatic carboxamides (preferably N,N-di(C.sub.1 -C.sub.4 alkyl)C.sub.1 -C.sub.2 carboxamides), lactams and cyclic and acyclic urea derivatives, and mixtures thereof. These solvents are preferably used in dried form.
The following are specific examples thereof: dimethyl sulfoxide, sulfolane, dimethyl formamide, diethyl formamide, dibutyl formamide, dimethyl acetamide, diethyl acetamide, dibutyl acetamide, N-formylmorpholine, N-methylpyrrolidone, 1,3'-dimethylimidazolidin-2-one, 1,3'-dimethyltetrahydropyrimidin-2-one, and tetramethyl urea.
For the purposes of the invention, dimethyl formamide and, in particular, dimethyl acetamide are preferred.
The amount of solvent is not critical and is usually from 10 to 200 moles, preferably from 40 to 60 moles per mole of perylimide (II).
Suitable inorganic bases are primarily the alkali metal salts (lithium and preferably sodium and potassium salts) of weak inorganic acids such as carbonic acid and phosphoric acid, and also mixtures of these salts.
The following can be cited as being particularly suitable examples: sodium bicarbonate and potassium hydrogen carbonate and also trisodium phosphate and preferably sodium carbonate and potassium carbonate.
There are normally used, per mole of perylimide (II), from 2 to 10 mol and preferably from 2 to 5 mol of inorganic base.
Suitable alkylating agents are the a

REFERENCES:
patent: 4585878 (1986-04-01), Jost et al.
patent: 5017713 (1991-05-01), Kondo et al.

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