WO2000026189A1 - Method for producing nitroxyl compounds of secondary amines - Google Patents

Abstract

The invention relates to a method for producing nitroxyl compounds of secondary amines which do not carry any hydrogen atoms on the alpha -carbon atoms. According to said method, amines of this type are oxidised with hydrogen peroxide in the presence of an acidic substance.

Description

Process for the preparation of nitroxyl compounds of secondary amines

description

The present invention relates to a process for the preparation of nitroxyl compounds of secondary amines which do not have any hydrogen atoms on the α-carbon atoms by oxidation of such amines with hydrogen peroxide, the oxidation being carried out in the presence of an acidic substance.

Various processes are known for producing nitroxyl compounds.

4-Substituted 2, 2, 6, 6-tetramethylpiperidine-N-oxylene is prepared starting from the corresponding amine in accordance with US Pat. No. 4,665,185 by oxidation with t-butyl hydroperoxide using transition metal catalysts.

In the publications by G. Sosnovsky et al. , Z. Naturforsch. 31b, 1376 (1976); J. J. Zakrzewski, J. Prakt. Chem., 327 (6). 1011 (1985) and E.G. Rozantsev et al. , Synthesis, 1971. 190 describes the preparation of 4-substituted 2, 2, 6, 6-tetramethylpiperidine-N-oxylene starting from the corresponding amine by oxidation with hydrogen peroxide using sodium tungstate as a catalyst.

European patent application 0 574 667 describes a process for the preparation of 2, 2, 6, 6-tetramethylpiperidine-N-oxyl and its derivatives substituted in the 4-position by oxidation of the corresponding amines with hydrogen peroxide with catalysis of divalent metal salts, alkaline earth metal -, In particular magnesium and zinc salts are preferably used.

According to M.E.Brik, Tetrahedron Letters, 3_6_ / 5519 (1995), nitroxyl compounds are obtained by oxidation of secondary amines with potassium peroxomonosulfate in buffered aqueous solutions.

In the publication by EJRaukman et al. , Syn. Communications 5 _. (6), 409 (1975) describes, inter alia, the preparation of nitroxyl compounds starting from the corresponding amine by oxidation in the presence of acetonitrile, methanol, hydrogen peroxide and sodium bicarbonate using sodium tungstate as a catalyst. The document WO 97/17327 describes the preparation of 4-hydroxy- and 4-acylamino-2, 2, 6, 6-tetramethylpiperidine-N-oxyl by oxidation of the corresponding amine with hydrogen in the absence of a catalyst at temperatures of 80-99 ° C or in the presence of a catalytic amount of an ammonium or alkali metal carbonate or bicarbonate at temperatures of 60-99 ° C.

A disadvantage of most of the preparations mentioned is that they usually only yield yields of the desired nitroxyl compound in the range of 73-85% and partly take place under heavy metal catalysis, which is economical and / or ecological, especially with regard to the large-scale production of Nitroxyl compounds is unsatisfactory.

According to document WO 97/17327, yields of over 90% of the desired nitroxyl compound can be achieved throughout, but it is still unsatisfactory that a disproportionately high proportion of hydrogen peroxide must be used to achieve these yields.

The object was therefore to provide a process for the preparation of nitroxyl compounds which does not have these disadvantages of the prior art.

It has been found that the production of nitroxyl compounds of secondary amines which do not have any hydrogen atoms on the α-carbon atoms can be advantageously achieved by oxidizing such amines with hydrogen peroxide if the oxidation is carried out in the presence of an acidic substance.

At least one substance selected from the group consisting of inorganic acids, organic acids, inorganic acidic solids and organic acidic solids is preferably used as the acidic substance. Usually you will only use an acidic substance, but in individual cases you can also use a mixture of acids from one or from different of the classes mentioned.

In the case of the inorganic acids, sulfuric acid and phosphoric acid should be mentioned in particular. In individual cases, peroxomono- or disulfuric acid, optionally in a mixture with sulfuric acid, can also be used. Accordingly, a reduction in the amount of hydrogen peroxide required for the oxidation of the secondary amine is possible. Organic acids include formic acid and acetic acid. Of course, you can also use the corresponding peroxyacids in individual cases, ie peroxo-formic or peroxoacetic acid, optionally in a mixture with formic or acetic acid, with a corresponding reduction in the amount of hydrogen peroxide required.

Inorganic acidic solids are to be understood

A) doped layered silicates which have negative layer charges saturated by protons, or inorganic solids which contain such doped layered silicates as an essential constituent,

B) Zeolites in the acidic H form or inorganic solids which contain such zeolites as an essential component or

C) mixed oxides containing acidic centers or inorganic solids which contain such mixed oxides as an essential constituent, the mixed oxides consisting of a combination of (a) oxides of titanium, zirconium, hafnium, tin, iron or Cr (III) on the one hand with (b ) Oxides of vanadium, chromium (VI), molybdenum, tungsten or scandium on the other hand, or the mixed oxides are sulfated or phosphated oxides of group (a) and the mixed oxides have been calcined after their combination at temperatures of 450 to 800 ° C.

The compounds of group A) to be used according to the invention as acidic substances are above all aluminum silicates. They belong to the clay minerals and are made up of Si0 tetrahedron and Al ₂ θ ₃ octahedron layers, part of the silicon in the tetrahedron layer being formed by trivalent cations, preferably aluminum and / or part of the aluminum in the octahedral layer being preferably by divalent cations Magnesium is replaced, so that negative stratified charges arise.

Layered silicates with negative charges occur naturally in the form of montmorillonites, vermiculites or hectorites or can also be synthesized.

Further details are ZM Thomas and WZ Thomas, Principles and Practice of Heterogeneous-Calalysis, 1997, Vetc. ISBN 3-527-29239-8, p. 347 ff. Montmorillonite, which occurs naturally and is converted into the H form by acid treatment, is preferably used as the acidic group A) substance.

Montmorillonite is an example

Na ₀ , 33UAlι, 67Mgo, 33) (OH) ₂ [Si ₄ Oι ₀ ] ^} with stratified charges of about 0.6 to 0.2 per formula unit.

For the partial or complete proton saturation of the negative layer charges, the exchangeable cations contained in the natural or synthetic layer silicates, usually alkali or alkaline earth ions, are exchanged for protons. This is done in a manner known per se, e.g. by treatment with sulfuric acid or hydrochloric acid.

Since the protons are less temperature stable than layer silicates containing alkali or alkaline earth ions, so-called "pillared clays", in which the layers are supported against one another, can also be used as acidic substances. The production of such "pillared clays" is in Figuras, Catal. Rev. Be. Closely. 30 (1988) 457 and Jones, Catal. Today (2 (1988) 357. The information given there is hereby incorporated by reference and is intended to be incorporated here.

In particular, layered silicates with negative layer charges, which are saturated by protons, are: montmorillonite, vermiculite and hectorite.

As acidic substances of group B), zeolites come in the acid H form of the structure types MFI, MEL, BOG, BEA, EMT, MOR, FAU, MTW, LTL, NES, CON or MCM-22 according to the structure classification from WM Meier, DH Olson, Ch.Baerlocher, Atlas of Zeolithe Structure Types, Elsevier, 4 ^th ed., 1996.

The acid H form of 12-ring zeolites of the BETA, Y, EMT and mordenite structure type, and 10-ring zeolites of the Pentasil type are preferred. In addition to the elements aluminum and silicon, the zeolites can also contain boron, gallium, iron or titanium in the framework. They can also be partially exchanged with elements of the IB, IIB, IIIB, IIIA or VIIIB group, as well as with the elements of the lanthanides. In particular, the zeolites ZBM-20, Fe-H-ZSM5, Sn-beta zeolite, beta zeolite, Zr-beta zeolite, H-beta zeolite, H-mordenite, USY, Ce-V zeolite, HY zeolite, Ti / B beta zeolite, B beta zeolite or ZB-10 are considered as acidic substances.

Zeolites in the acidic H form and their preparation are described in detail in the literature. For this reason, reference is made to the summary in R. Szostak, Handbook of Molecular Sieves Van Nostrand Reinhold, New York, ISBN 0-442-31899-5, and reference is hereby made to the information provided there.

Acidic substances of group C) include, in particular, so-called superacid mixed oxides, which have been described several times in the literature. For example, R.J. Gillespie, Acc. Chem. Res. 1, (1968) 202 and R.J. Gillespie and T.E. Peel, Adv. Phys. Org. Chem. 9 (972) 1.

Special superacidic metal oxides which are suitable as acidic substances of group C) for the production of nitroxyl compounds according to the invention are described by Kazushi Arata in Applied Catalysis A: General 146 (1996) 3-32. Reference is made to the information in this literature reference regarding the superacid metal oxides and their preparation and they are to be considered incorporated here.

Suitable sulfated or phosphated metal oxides (a) of group C) are, in particular, phosphated or sulfated zirconium oxide or titanium oxide, which may also contain further elements, such as iron, cobalt or manganese.

Sulfated or phosphated compounds as acidic substances are in particular:

Zr0 ₂ S0 ₄ (S content 0.5 to 4 mol%) Zr0 ₂ P ₂ O ₅ (P ₂ 0 ₅ content 3 to 20 mol%)

Fe ₂ 0 ₃ P ₂ 0 ₅ (P ₂ 0 ₅ content 3 to 20 mol%)

Co / Mn / Zr0 ₂ S0 ₄ (S content 0.5 to 4 mol%);

Co / Mn content 0.1 to 5 mol%)

Fe / Mn / Zr0 ₂ S0 ₄ (S content 0.5 to 4 mol%; Fe / Mn content 0.1 to 5 mol%)

Superacid mixed metal oxides (a) and (b) of group C) are in particular those which contain zirconium, titanium, iron, tin or chromium on the one hand and tungsten or molybdenum on the other hand. In particular, Ti0 ₂ W0 ₃ , Fe ₂ 0 ₃ W0 ₃ , Zr0 ₂ Mo0 ₃ , Zr0 ₂ W0 ₃ , Cr ₂ 0 ₃ W0 ₃ , W0 ₃ Ti0, Ti0 ₂ W0 ₃ or Sn0 ₂ W0 ₃ Si0 ₂ should be mentioned, wherein the molar ratio of the oxides of group (a) to group (b) is usually 70 to 30 to 90 to 10.

Organic acidic solids are to be understood

D) Ion exchange resins in their protonated form.

For example, these are phenol / formaldehyde resins and polymers of styrene and copolymers of styrene and divinylbenzene, each of which contains sulfonyl and / or carboxyl groups as acidic groups.

As a commercially available ion exchange resins may be mentioned here are those of the brands Amberlite ^® and Amberlyst (Fa.Aldrich).

One approach (a) to carry out the method according to the invention is e.g. in that the total amount of the amine and the acidic substance, if appropriate in a suspending, emulsifying or solvent (hereinafter such a suspending, emulsifying or solvent is also referred to as SEL agent), the desired Setting the temperature and adding the hydrogen peroxide in portions or continuously.

A further procedure (b) for carrying out the process according to the invention consists, for example, in that part of the amine and the total amount of the acidic substance, if appropriate in a SEL agent, are initially introduced, the desired temperature is set and the remaining part of the amine and the hydrogen peroxide are added in portions or continuously admits that the addition of the remaining amine and the hydrogen peroxide is completed at about the same time.

A further procedure (c) for carrying out the process according to the invention consists, for example, in that a portion of the amine and the acidic substance, if appropriate in a SEL agent, is initially introduced, the desired temperature is set and the remaining portion of the amine and the remaining portion of the acidic Substance as a mixture and the hydrogen peroxide are added in portions or continuously in such a way that the addition of the remaining amine (and the remaining acidic substance) and the hydrogen peroxide has ended approximately at the same time.

A further procedure (d) for carrying out the process according to the invention consists, for example, in that part of the amine and the acidic substance, if appropriate in a SEL agent, The desired temperature is set and the remaining part of the amine and the hydrogen peroxide and the remaining part of the acidic substance are added in portions or continuously in such a way that the addition of the remaining amine and the hydrogen peroxide (and the remaining acidic substance) approximately simultaneously is finished.

A further procedure (e) for carrying out the process according to the invention consists, for example, in that the acidic substance or part of the acidic substance, if appropriate in a SEL agent, is initially introduced, the desired temperature is set and the amine, if appropriate in a mixture with the remaining portion of the acidic substance, and the hydrogen peroxide, optionally in a mixture with the remaining part of the acidic substance, added in portions or continuously such that the addition of the amine (and optionally the remaining acidic substance) and the hydrogen peroxide (and optionally the remaining acidic substance ) has ended at about the same time.

If procedure (b) is followed, the remaining part of this amine is advantageously added in the case of a solid amine and, if possible, in the form of a solution, otherwise as a suspension or emulsion.

If one proceeds according to procedure (c) or (d), it is advantageous to add at least one liquid inorganic or organic acid or its aqueous solution as an acidic substance.

If one proceeds according to procedure (c), the mixture of the remaining part of the amine and the remaining part of the acidic substance is preferably and if possible as a solution, otherwise as a suspension or emulsion. Suitable acidic substances here are inorganic or organic acids which are soluble in the SEL agent used or are miscible with the SEL agent used. Furthermore, the ammonium compound formed or formed (from the starting amine and the acidic substance) should also be soluble in this SEL agent in order to ensure the most defined dosage possible.

If procedure (d) is followed, the remaining part of the amine, if it is liquid, can also be added as a pure substance, if possible in the form of a solution, or else as a suspension or emulsion. In the case of solid amines, a SEL agent is advantageously used. As the acidic substance, preference is given to inorganic or organic acids which are soluble in hydrogen peroxide or with hydrogen peroxide are miscible, the term "hydrogen peroxide" being understood here and elsewhere as meaning its aqueous solution.

If you proceed according to procedure (e), the comments made on procedures (b) to (d) apply analogously and depending on whether part of the acidic substance should be added to the starting amine or the hydrogen peroxide.

If the submitted amine or, if appropriate, its adduct with the acidic substance which is used for the preparation of the corresponding nitroxyl compound is liquid under the oxidation conditions, a SEL agent can be dispensed with. Through the addition of (aqueous solution of) hydrogen peroxide and with progressive oxidation of the amine or adduct to the nitroxyl compound, water is inevitably added or water is additionally formed, which can be regarded as a SEL agent.

In the case of a starting amine or, if appropriate, a corresponding adduct with the acidic substance which is solid under the oxidation conditions, this amine or adduct is preferably mixed with a SEL agent.

In a preferred embodiment of the process according to the invention, the oxidation is carried out in the presence of a SEL agent which consists of water, an organic liquid which is at least partially miscible with water or a mixture of water and such an organic liquid.

Organic liquids which are at least partially miscible with water are, for example, C ₁ -C ₄ -alcohols, such as methanol, ethanol, n- or i-propanol, n-, i-, sec- or tert-butanol, C ₂ -C ₆ -Diols, such as ethylene glycol, propylene glycol, 1,4-butanediol, 1, 6-hexanediol, oligomeric and polymeric ethylene and propylene glycols (polyethylene glycols or polypropylene glycols) and their Cχ-C-alkyl, especially their methyl ethers , cyclic

Ethers such as Tetrahydrofuran or 1,4-dioxane, ketones, e.g. Acetone, methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone or methyl tert-butyl ketone, and also C 1 -C 8 -carboxylic acid C 1 -C 4 -alkyl esters, such as e.g. the methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl or tert-butyl ester of formic, acetic, propionic or butyric acid.

These organic liquids can also be mixed with one another or such a mixture of organic liquids in a mixture with water can also be used as the SEL agent. Preferred organic liquids are C 1 -C 4 -alcohols, such as, for example, methanol, ethanol, n- or i-propanol, n-, i-, sec- or tert-butanol.

Methanol, ethanol, n- or i-propanol are particularly preferably used as organic liquids.

Water, methanol, ethanol, n- or i-propanol or mixtures of these liquids with one another are preferably used as SEL agents.

Oxidation of the amine is usually accomplished in the absence of a SEL agent (apart from the amount of water that results from the addition of the aqueous solution of hydrogen peroxide and the reduction of the hydrogen peroxide to water)

Temperatures from 50 ° C to the boiling point of the water.

In the presence of a SEL agent, the oxidation of the amine is usually carried out analogously to what has been said at temperatures from 50 ° C. to the boiling point of the lowest-boiling component of the SEL agent.

The oxidation is usually carried out in the temperature range from about 20 ° C. below the boiling temperature (the lowest-boiling component) of the SEL agent to the boiling temperature (the lowest-boiling component) of the SEL agent.

The temperatures mentioned are understood as those temperatures which are set in the template. The hydrogen peroxide (optionally mixed with acidic substance, see procedure (d)) is usually not preheated. The remaining amine (see procedure (b), optionally mixed with acidic substance, see procedure (c)) or its solution, suspension or emulsion can be preheated if desired, but this is usually not used.

If the oxidation of the starting amine is carried out in the presence of a SEL agent which consists predominantly of water or is water, the reaction is advantageously carried out in such a way that a pH of the suspension or solution of about 8.3 (at the temperature of the reaction measured) is not exceeded or, if this value is exceeded for a short time, the pH is adjusted to the mentioned range again by adding acidic substance. The process according to the invention is preferably used to prepare nitroxyl compounds, which are secondary amines of the formulas Ia

or Ib

R R

R C I N C R (Ib)

I.

R H R

underlie. Denote in these formulas

R ¹ and R ^2, independently of one another, are each C 1 -C 4 -alkyl, phenyl or, together with the C atom to which they are attached, a 5- or 6-membered saturated hydrocarbon ring,

R ^{3 is} hydrogen, hydroxy, amino, S0 ₃ H, S0 ₃ M, P0 ₃ H ₂ , PO ₃ HM, P0 ₃ M ₂ , organosilicon radicals or an m-valent organic or silicon-organic radical bonded via oxygen or nitrogen , where M stands for an alkali metal,

R ^{4 is} hydrogen, -CC ₂ -alkyl, Cχ-C ₁₂ alkoxy or together with

R ^{3 is} oxygen or, together with R ³ and the carbon atom to which they are attached, the following ring structures

where for the cases in which R ³ forms a common residue with R ⁴ , m = 1, R ^{5 is} hydrogen, -CC ₂ -alkyl or - (CH ₂ ) _z -COOR ⁶ ,

R ^{6 are the} same or different Cι-Cιg alkyl,

k 0 or 1,

z and p each independently represent an integer from 1 to 12 and

m is an integer from 1 to 100 and

R is the same or different C 1 -C 4 alkyl, C ₅ -C ₇ cycloalkyl, C ₇ -Cχo aralkyl or C ₆ -C aryl

mean.

As C 1 -C 4 alkyl for R ¹ and R ² are methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl or tert-butyl or R ¹ and R ² form together a tetra or pentamethylene bridge. R ¹ and R ² are preferably the same. R ¹ and R ² are particularly preferred methyl groups.

As Cι ~ C für ₂ alkyl for R ⁴ come in addition to the aforementioned Cχ-C alkyl groups also pentyl, sec-pentyl, tert-pentyl, neopentyl, 2, 3-dimethyl-but-2-yl, n-hexyl, 2-methylpentyl, n-heptyl, 2-methylhexyl, 2-ethylhexyl, n-octyl, isooctyl, 2-ethylhexyl, nonyl, 2-methylnonyl, isononyl, 2-methyloctyl, n-decyl, isodecyl, 2- Methylnonyl, n-undecyl, isoundecyl, n-dodecyl and isododecyl, (the designations isooctyl, isononyl and isodecyl are trivial designations and derive from the carbonyl compounds obtained after oxosynthesis; see also Ulimann's Encyclopedia of Industrial Chemistry, 5th Edition , Vol. AI. Pages 290-293, and Vol. A10, Pages 284 and 285).

The C 1 -C ₂ alkoxy radicals which are suitable for R ⁴ can be derived accordingly from the C 1 -C 4 alkyl radicals.

p is preferably an integer from 6 to 12, particularly preferably 9.

z is preferably an integer from 1 to 4, particularly preferably 2.

In addition to hydrogen, R ⁵ includes, for example, the C 1 -C ₂ -alkyl radicals mentioned above. R ⁵ preferably represents hydrogen, Cχ-C-alkyl, which has already been mentioned above by way of example, or (CH ₂ ) _z -COO (-CC ₁₆ alkyl), where -CC ₆ alkyl, for example under Cχ-Cχs-alkyl is listed below. The radicals -CH ₂ -CH -COO (CH ₂ ) ₁₁ -CH ₃ and -CH ₂ -CH ₂ -COO (CH ₂ ) ₁₃ -CH ₃ are particularly preferred.

C 1 -C ₈ alkyl for R ⁶ is, for example, one of the above-mentioned C ₂ alkyl groups, n-tridecyl, isotridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl or n-octadecyl . N-Dodecyl and n-Hexadecyl are preferred.

Preferred monovalent radicals R ³ are hydrogen, the Cχ-C-alkyl groups already mentioned above and organosilicon radicals of the formula

T

Si T T

where the groups T may be the same or different from one another and denote C Ci-Ci ₂ alkyl or phenyl. Cχ-Cχ ₂ alkyl radicals have already been mentioned as examples under radical R ⁴ .

Examples of such organosilicon radicals are

CH ₃ CH ₃ CH ₃ CH ₃ CH ₃

^• Si (CH ₃ ) ₃ , -Si (C ₂ H ₅ ) ₃ , Si C- -CH -Si - C —CH ₃ as well

CH ₃ CH ₃ CH ₃ II

CH ₃ CH ₃

-Si (C ₆ H ₅ ) ₃

Li, Na and K are preferably used as alkali metals M in the groups -SO ₃ M, -PO ₃ HM and -Pθ _{3 2} .

Further preferred monovalent groups R ³ are hydroxy, a group of the formula

wherein R ⁷ Cχ-Cχ ₈ "alkyl - for example, corresponding radicals have already been mentioned above - vinyl or isopropenyl and k is either 0 or 1. Here, particular preference is given to those radicals in which k is 0 and R ⁷ Cχ-C alkyl are, that is Cχ-C alkoxy, such as methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, sec-butoxy and tert-butoxy.

Further preferred monovalent groups R ³ are also the oxygen-bonded siloxane residues derived from the above organosilicon residues.

Preferred m-valent radicals R ³ are, for example, the following radicals

0 R ⁹ QR ⁹

R8 R8 c c

N— - (CH ₂ ) _X N, N (CH ₂ ) _X ,

0 oo— - C (CH ₂ ) - C - o- - or

worin R⁸ Cχ-C₁₂-Alkyl oder - (CH₂) _z-C00R⁶

wherein R ^{8 is} Cχ-C ₁₂ alkyl or - (CH ₂ ) _z -C00R ⁶

R ^{9 is} hydrogen or Cχ-Cχs-alkyl,

k either 0 or 1 and

x is an integer from 1 to 12, z and R ⁶ have the meaning already given above.

For example, Cχ-C und ₂ alkyl and the group - (CH ₂ ) _z -C00R ⁶ for R ^{8 have} already been listed for R ⁵ . The preferences made there also apply here. For example, Cχ-C fürs-alkyl for R ^{9 has} already been mentioned above for R ⁶ . R ⁹ preferably represents hydrogen.

Further preferred m-valent radicals R ³ are, for example, the following

wobei

in which

R ¹⁰ C ₈ -C ₂₂ alkyl,

^{U is} hydrogen or an organic residue,

x is an integer from 1 to 12 and

n is an even number m.

If R ^{3 is} one of these radicals, R ^{4 is} preferably hydrogen, m can mean an integer from 1 to 100. M is preferably 1, 2, 3, 4 or an integer from 10 to 50, with mixtures (with a corresponding molecular weight distribution) usually being used, particularly in the case of the oligomeric or polymeric radicals R ³ , so that, owing to such statistical distributions, as a rule fractional values for m result.

When R ⁱ ° for example, the already exemplified above Cs-Cχ come ₈ -alkyl radicals, and n-nonadecyl, n-eicosyl, n-Unei- cosyl and n-doeicosyl. Mixtures of different radicals R ¹⁰ , which differ in the length of the carbon chain, are preferred.

Other suitable amines as starting materials for the production of N-oxylene according to the invention are also oligomeric or polymeric compounds which have a polysiloxane as the main polymer chain and in the side chain with 2, 2, 6, 6-tetraalkylpiperidine, preferably with 2, 2, 6, 6 tetramethyl piperidine rings are substituted. Examples of amino compounds which can serve as corresponding starting materials in the process according to the invention can be found e.g. in the document WO 96/17002.

Preferred secondary amines as starting material for the production of nitroxyl compounds according to the invention are

2,2,6,6-tetramethylpiperidine,

2,2,6, 6-tetramethyl -1,2,3,6-tetrahydropyridine

2,2,6, 6-tetramethylpiperidin-4-ol,

2,2,6,6-tetramethyl-4-methoxypiperidine, 2,2,6,6-tetramethyl-4-trimethylsiloxypiperidine,

2,2,6, 6-tetramethylpiperidin-4-one,

2,2,6,6-tetramethylpiperidin-4-yl acetate,

2,2,6,6-tetramethylpiperidin-4-yl-2-ethylhexanoa,

2,2,6,6-tetramethylpiperidin-4-yl stearate, 2,2,6,6-tetramethylpiperidin-4-yl benzoate,

2,2,6,6-tetramethylpiperidin-4-yl- (4-tert-butyl) benzoate,

Bis (2,2,6, 6-tetramethylpiperidin-4-yl) succinate, Bis (2,2,6, 6-tetramethylpiperidin-4-yl) adipate,

Bis (2,2,6,6-tetramethylpiperidin-4-yl) sebacate,

Bis (2,2,6, 6-tetramethylpiperidin-4-yl) -n-butylmalonate,

Bis (2,2,6, 6-tetramethylpiperidin-4-yl) phthalate, bis (2,2,6, 6-tetramethylpiperidin-4-yl) isophthalate,

Bis (2, 2, 6, 6-tetramethylpiperidin-4-yl) terephthalate.

Bis (2,2,6, 6-tetramethylpiperidin-4-yl) hexyhydroterephthalate,

N, N 'bis (2,2,6, 6-tetramethylpiperidin-4-yl) adipinamide,

N- (2, 2, 6, 6-tetramethylpiperidin-4-yl) -caprolactam, N- (2, 2, 6, 6-tetramethylpiperidin-4-yl) -dodecylsuccinimide,

2,4,6-tris- [N-butyl-N- (2,2,6,6-tetramethylpiperidin-4-yl] -s-triazine,

N, N'-bis (2,2,6,6-tetramethylpiperidin-4-yl) -N, N'-bis-formyl -1,6-diaminohexane, 4,4'-ethylene bis (2,2,6,6 6-tetramethylpiperazin-3-one) and

Tris- (2,2,6,6-tetramethylpiperidin-4-yDphosphite.

Examples

example 1

5 250 g (1.75 mol) of 2, 2, 6, 6-tetramethylpiperidin-4-ol (from Hüls; hereinafter referred to as TAA-ol), 30 ml of 85% phosphoric acid (0.439 mol) and 150 ml of distilled Water was heated to 90 ° C. and then 302 ml of 30% hydrogen peroxide solution (2.96 mol hydrogen peroxide) were metered in over the course of 4 h. The temperature rose in the meantime to 99 ° C. After the addition of the hydrogen peroxide solution had ended, stirring was continued at 91 ° C. for 1.5 h. The conversion of TAA-ol to the corresponding nitroxyl compound was 94% of the theoretically expected conversion (determined by gas chromatography). 5

Example 2

230 ml of distilled water were placed in a reactor and heated to 90 ° C. with stirring. Subsequently, as acidic substance sub- 0 30 g Amberlyst ^® 15 (Fa.Aldrich) was added. 110 ml and a further 40 ml of 30% aqueous hydrogen peroxide solution (in total 1.47 mol hydrogen peroxide) were metered in continuously within 25 min. At the start of the hydrogen peroxide addition, a solution of 150 g of TAA-ol (1.05 mol; 5 Fa. Hüls) in 1000 ml of distilled water was metered in so that the pH of the reaction mixture remained below 8.1. The addition of the TAAol solution was complete within about 11 hours. The mixture was then left to stir at 98 ° C. for a further 12 h. The conversion of the TAA-ol to the corresponding nitroxyl compound was 100% of the theoretically expected turnover (determined by gas chromatography).

5

0

5

Claims

claims 1. A process for the preparation of nitroxyl compounds of secondary amines which do not have any hydrogen atoms on the α-carbon atoms by oxidation of such amines with hydrogen peroxide, characterized in that the oxidation is carried out in the presence of an acidic substance. 2. The method according to claim 1, characterized in that at least one substance selected from the group consisting of inorganic acids, organic acids, inorganic acidic solids and organic acidic solids is used as the acidic substance. 3. The method according to claim 1 or 2, characterized in that one carries out the oxidation in the presence of a suspending, emulsifying or solvent which consists of water, an at least partially miscible organic liquid or a mixture of water and such an organic liquid consists. 4. Process according to claims 1 to 3, characterized in that secondary amines of the formulas Ia

or Ib R- N (Ib) MR used in which R ⁱ and R ² independently of one another in each case Cχ-C ₄ -alkyl, phenyl or together with the C atom to which they are attached, a 5- or 6-membered saturated hydrocarbon ring, R ^{3 is} hydrogen, hydroxy, amino, S0 ₃ H, SO ₃ M, PO ₃ H ₂ , PO ₃ HM, PO ₃ M ₂ , organosilicon radicals or an m-valent organic or organosilicon radical bonded via oxygen or nitrogen, where M is there is an alkali metal, R ^{4 is} hydrogen, Cχ-Cχ alkyl, Cχ-Cχ ₂ alkoxy or together with R ³ oxygen or together with R ³ and the C atom to which they are attached, the following ring structures

where for the cases in which R ³ forms a common residue with R ⁴ , m = 1, R ^{5 is} hydrogen, Cχ-C ₁₂ alkyl or - (CH ₂ ) _z -C00R ⁶ , R ^{6 is the} same or different Cχ-Cχs alkyl, k 0 or 1, z and p are each independently 1 to 12 and ml to 100 and R is the same or different Cχ -Cχ ₂ alkyl, C ₅ -C ₇ cycloalkyl, C ₇ -Cχo aralkyl or C ₆ -Cχ ₄ aryl mean.