WO2004031150A1

WO2004031150A1 - Oxoammonium salts of 1-oxy-2,2,6,6-tetramethyl-1-piperidine (tempo) and their use as oxidizing agents

Info

Publication number: WO2004031150A1
Application number: PCT/EP2003/010834
Authority: WO
Inventors: Dario Lazzari; Massimiliano Sala; Grazia Baravelli
Original assignee: Ciba Specialty Chemicals Holding Inc.; Ciba Specialty Chemicals S.P.A.
Priority date: 2002-10-07
Filing date: 2003-09-30
Publication date: 2004-04-15
Also published as: AU2003276010A1

Abstract

The invention relates to stable oxoammonium salts of hindered amines and to their use as oxidizing agent for the conversion of alcohols to the corresponding carbonyl derivatives.

Description

OXOAMMONIUM SALTS OF l-OXY-2 , 2 , 6 , 6-TETRAMETHYL- l- PI PERIDINE (TEMPO ) AND THEIR USE AS OXIDIZING AGENTS

The invention relates to stable oxoammonium salts of hindered amines, to their use as oxidizing agents and to an oxidation process for the conversion of alcohols to the corresponding carbonyl derivatives.

Selectivity is of primary importance in oxidation processes.

In the synthesis of aldehydes from primary alcohols, carboxylic acids are often formed as byproducts of the oxidation reaction (over-oxidation), and the oxidation of 1 ,2-diols or α-hydroxyketones are frequently accompanied by C-C chain cleavage reactions.

If unsaturated primary alcohols are involved, secondary reactions usually take place to a relatively great extent because the oxidizing agent also attacks the double bond and results in extensive decomposition of the molecule.

The selective oxidation of a secondary alcohol function in the presence of a primary alcohol function or vice versa is desired, without the respective other function being affected.

It is known to use nitroxyl radicals/oxoammonium salts to oxidize primary and secondary alcohols to the corresponding carbonyl derivatives. (Journal of Organic Chemistry, vol. 52 (12), pp. 2559-2562). In said paper it is proposed that oxoammonium salts derived from TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) react with alcohols forming the carbonyl derivatives and hydroxylamines.

WO 02/32913 describes an oxidation using elemental halogen as oxidant in the presence of an oxoammonium catalyst/halide co-catalyst system. A source of the oxoammonium catalyst is 2,2,6,6-tetramethylpiperidinyl-l-oxy (TEMPO) and a particularly economical and effective catalyst is 4-acetylamino-2,2,6,6-tetramethylpiperidinyl-1-oxy.

The use of pure oxoammonium salts as oxidizing agents avoids this over-oxidation to the acid from the corresponding primary alcohol and allows the use of a water-free system, which is particularly useful for a water-sensitive product or for a water-soluble oxidation product. If the reaction mixture is heterogeneous (water/organic), the work-up of the oxidation products is often very difficult and a product recovery is complicated and often incomplete.

In order to have removable oxoammonium salts from the reaction, generally, an expensive method is employed (e.g. the oxoammonium salts supported on resin and used as oxidizing agent, Angew Chem. Int. Ed. 2001, 40, No.8 1436-1439, in which the synthesis requires the use of sodium hydride).

It is an object of the present invention to provide further oxoammonium salts which are stable at room temperature and insoluble in organic solvents and which can easily be removed from the reaction mixture after the oxidation reaction and can easily be recycled.

It has been found that oxoammonium salts of compounds comprising units of sterically hindered amines fulfill the above requirements.

Such sterically hindered amines are from the class of the 2,2,6,6-tetrasubstituted piperidines. They may be polymeric, and may have a very large variety of substituents in position 4 of the piperidine ring.

The invention relates to oxoammonium salts of monomeric or polymeric hindered amines containing at least two structural elements of formula (A)

wherein

Z is -NH, -NOH, -NO⁰ or -N⁺=O X^" with the proviso that at least one of Z is -N⁺=O X^" with X being Cl, Br, F, J; and ^* denotes a valence.

Preferred are sterically hindered amines which are disclosed in US-Patent 6,441,166 and which correspond to the formula (I) as defined under a), the formula (II) as defined under b), the formula (VI) as defined under d), the formula (VII) as defined under e), the formula (XII) as defined under j), the formula (XIII) as defined under k), and sterically hindered amines of the formula (V) as defined under c), the formula (VIM) as defined under f), the formula (IX) as defined under g), the formula (X) as defined under h), the formula (XI) as defined under i),

Preferably the oxoammonium salts are of the formulae I, II, V-XIII a) a of the formula (I)

in which Z is -NH, -NOH, -NO° or -N⁺=O X^" with the proviso that at least one of Z is -N⁺=O X^~ with X being Cl, Br, F, J;

R₂ is Cι-C₁₄alkylene or bis{(C₁-C₂₀alkyl)oxycarbonyl}C₄-C₁₀alkanetetrayl (if

is 2), and Pi₂ is C₄-Cι₀alkanetetrayl (if

is 4);

b) of the formula (II)

in which

R₃ and R₇ independently of one another are hydrogen or CrC^alkyl;

R₄, R₅ and R₆ independently of one another are C₂-C₁₀alkylene; and

Xi. X₂. X₃. X₄, X5, Xβ, X7 and X₈ independently of one another are a group of the formula (III) or (IV)

in which Z is -NH, -NOH, -NO° or -N⁺=O X^" with the proviso that at least one of Z is -N⁺=O X^" with X being Cl, Br, F, J; R₈ is hydrogen, d-C^alkyl, C₅-Cι₂cycloalkyl, d-C alkyl-substituted C₃-C₁₂cycloalkyl, phenyl, -OH- and/or Cι-C₁₀alkyl-substituted phenyl, C₇-C₉phenylalkyl, C₇-C₉phenylalkyl which is substituted on the phenyl radical by -OH and/or d-doalkyl; or a group of the formula (IV);

c) of the formula (V)

in which is hydrogen, d-C^alkyl, C₅-d₂cycloalkyl or phenyl;

is a group of the formula (IV) (IV)

in which

Z is -NH, -NOH, -NO° or -N⁺=O X^" with the proviso that at least one of Z is -N⁺=O X^" with X being Cl, Br, F, J;

d) of the formula (VI)

in which

R₁₁. R₁₃. Ri₄ and R₁₅ independently of one another are hydrogen, d-C₁₂alkyl, C₅-C₁ cyclo- alkyl, d-C₄alkyl-substituted C₅-Cι₂cycloalkyl, phenyl, -OH- and/or d-C,₀alkyl- substituted phenyl, C₇-C₉phenylalkyl, C₇-C_phenylalkyl which is substituted on the phenyl radical by -OH and/or Ci-Cioalkyl; or a group of the formula (IV) as defined under b); R₁ is C₂-Cι₈alkylene, C₅-C₇cycloalkylene or d-C₄alkylenedi(C₅-C₇cycloalkylene), or the radicals Rn, R₁₂ and R₁₃, together with the nitrogen atoms to which they are attached, form a 5- to 10-membered heterocyclic ring; or R₁₄ and Bis. together with the nitrogen atom to which they are attached, form a 5- to

10-membered heterocyclic ring; n₂ is a number from 2 to 50, and at least one of the radicals Rn, R₁₃, R₁ and R₁₅ is a group of the formula (IV)

(IV) in which

Z is -NH, -NOH, -NO⁰ or -N⁺=O X^" with the proviso that at least one of Z is

-N⁺=O X^" with X being Cl, Br, F, J

e) of the formula (VII)

in which

Z is -NH, -NOH, -NO° or -N⁺=O X^" with the proviso that at least one of Z is -N⁺=O X^" with X being Cl, Br, F, J; R₁₆ is Cι-C₁₀alkyl, C₅-Cι₂cycloalkyl, C₁-C₄alkyl-substituted C₃-C₁₂cycloalkyl, phenyl or d-Cι₀alkyl-substituted phenyl; R₁₇ is C₃-Cι₀alkylene; n₃ is a number from 2 to 50;

f) of the formula (VIII)

in which t is a number from 2 to 18; R₁₈ is hydrogen, d-C₁₂alkyl, C₅-C₁₂cycloalkyl or phenyl;

X1₀ is a group of the formula (IV) (IV)

in which

g) of the formula (IX)

in which t is a number from 2 to 18;

R₁₉ and R₂₀ independently of one another are hydrogen, d-Cι₂alkyl, C₅-C₁₂cycloalkyl or phenyl or a group of the formula (II) or (IV); or

R₁₉ and R₂₀, together with the nitrogen atom to which they are attached, form a 5- to 10-membered heterocyclic ring which may be further interrupted by an O-atom;

Xn is a group of the formula (IV) (IV)

in which Z is -NH, -NOH, -NO⁰ or -N⁺=O X- with the proviso that at least one of Z is -N⁺=O X^" with X being Cl, Br, F, J;

h) of the formula (X)

in which t is a number of 2 to 18, q represent repeating units to reach a molecular weight of 2000-4000;

R₂₁ is hydrogen, d-C₁₂alkyl, C₅-C₁₂cycloalkyl or phenyl;

Λ12 is a group of the formula (IV) (IV)

in which

i) of the formula (XI)

in which t is a number from 2 to 18; m represent repeating units to reach a molecular weight of 2000-4000;

R₂₂ and R₂₃ independentliy of one another are hydrogen, d-C^alkyl, C₃-d₂cycloalkyl or phenyl or a group of the formula (III) or(IV); or R₂₂ and R₂₃, together with the nitrogen atom to which they are attached, form a 5- to 10-membered heterocyclic ring which may be further interrupted by an O-atom; R₂₄ is hydrogen, d-C₁₂alkyl, C₅-C₁₂cycloalkyl or phenyl;

C₁₃ is a group of the formula (IV) (IV)

in which

j) of the formula (XII)

1 [

"33 ,'35 '33

X 14 N- N - X 14

"34 (XII) in which

R₃₃ independently of one another are hydrogen, d-Cι₂alkyl or d-C₁₂acyl, and

R₃₄ and R₃₅ independently of one another are d-C₁₂alkyl;

X₁₄ is a group of the formula (IV) (IV)

in which

k) of the formula (XIII)

(XIII) R36. R37. R38. R39 and R₄₀ independently of one another are a direct bond or d-d₀alkylene, and n₇ is a number from 1 to 50;

X₁₅ is a group of the formula (IV) (IV)

in which

Z is -NH, -NOH, -NO° or -N⁺=O X^" with the proviso that at least one of Z is -N⁺=O X^" with X being Cl, Br, F, J.

Examples of alkyl having up to 30 carbon atoms are methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, 2-ethylbutyl, n-pentyl, isopentyl, 1-methylpentyl, 1 ,3-dimethyl- butyl, n-hexyl, 1-methylhexyl, n-heptyl, isoheptyl, 1 ,1 ,3,3-tetramethylbutyl, 1 -methylheptyl, 3-methylheptyl, n-octyl, 2-ethylhexyl, 1 ,1 ,3-trimethylhexyl, 1 ,1 ,3,3-tetramethylpentyl, nonyl, decyl, undecyl, 1-methylundecyl, dodecyl, 1 ,1 ,3,3,5,5-hexamethylhexyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, eicosyl, docosyl and triacontyl. One of the preferred meanings of R₂₃ and R₂₇ is Cι-C₂₅alkyl, especially Cι₅-C₂₅alkyl, for example hexadecyl and C₁₈-C₂₂alkyl. One of the preferred meanings of R ₅ is Cι-C₂₅alkyl, especially octadecyl. One of the preferred meanings of R₈ and R₁₉ is d-C alkyl, especially n-butyl.

Examples of Cι-C₄alkoxy are methoxy, ethoxy, propoxy and butoxy.

Examples of C₃-C₆alkenyl are allyl, 2-methallyl, butenyl, pentenyl and hexenyl. Allyl is preferred. The carbon atom in position 1 is preferably saturated.

Examples of C₅-d₂cycloalkyl are cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl and cyclododecyl. C₅-C₈cycloalkyl, especially cyclohexyl, is preferred.

d-dalkyl-substituted C₅-C₁₂cycloalkyl is for example methylcyclohexyl or dimethylcyclo- hexyl.

-OH- and/or CrC₁₀alkyl-substituted phenyl is for example methylphenyl, dimethylphenyl, trimethylphenyl, tert-butylphenyl or 3,5-di-tert-butyl-4-hydroxyphenyl. Examples of C₇-C₉phenylalkyl are benzyl and phenylethyl.

C -C₉phenylalkyl which is substituted on the phenyl radical by -OH and/or by alkyl having up to 10 carbon atoms is, for example, methylbenzyl, dimethylbenzyl, trimethylbenzyl, tert- butylbenzyl or 3,5-di-tert-butyl-4-hydroxybenzyl.

d-C₂₀acyl (e.g. C₂-C ₀acyl) is preferably d-C₂₀alkanoyl or C₂-C₂₀alkanoyl, C₃-C₂₀alkenoyl or benzoyl. Examples are formyl, acetyl, propionyl, butyryl, pentanoyl, hexanoyl, octanoyl, benzoyl, acryloyl and crotonoyl. d-C₁₀acyl (e.g. C₂-C₁₀acyl), in particular d-C₈acyl or C₂-C₈acyl such as d-C₈alkanoyl or C₂-C₈alkanoyl, C₃-C₈alkenoyl or benzoyl, especially acetyl, is preferred.

Examples of (Cι-C₈alkoxy)carbonyl are methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, hexoxycarbonyl, heptoxycarbonyl and octoxycarbonyl. One of the preferred meanings of A is (d-C₂alkoxy)carbonyl.

A particularly preferred example of (C₃-C₁₂cycloalkoxy)carbonyl is cyclohexoxycarbonyl.

Examples of (d-C₈alkyl)aminocarbonyl are methylaminocarbonyl, ethylaminocarbonyl, propylaminocarbonyl, butylaminocarbonyl, pentylaminocarbonyl, hexylaminocarbonyl, heptylaminocarbonyl and octylaminocarbonyl. (C C₄alkyl)aminocarbonyl is preferred.

A particularly preferred example of (C₅-C₁₂cycloalkyl)aminocarbonyl is cyclohexylamino- carbonyl.

A particularly preferred example of (C₇-C₉phenylalkyl)aminocarbonyl is benzylaminocarbonyl.

Examples of alkylene having up to 22 carbon atoms are methylene, ethylene, propylene, trimethylene, tetramethylene, pentamethylene, 2,2-dimethyltrimethylene, hexamethylene, trimethylhexamethylene, octamethylene and decamethylene. R₁₂ is preferably hexamethylene, R₃₆ and R₃₃ are preferably methylene, R₃₉ is preferably 2,2-dimethylethylene and R₄₀ 1 ,1-dimethylethylene.

An example of C₄-C₁₀alkanetetrayl is 1 ,2,3,4-butanetetrayl. An example of bis{(C₁-C₂₀alkyl)oxycarbonyl}C₄-C₁₀alkanetetrayl is bis{tridecyloxycarbonyl}- butanetetrayl.

An example of Cs-dcycloalkylene is cyclohexylene.

An example of d-C₄alkylenedi(C₅-C₇-cycloalkylene) is methylenedicyclohexylene.

An example of phenylenedi(d-C₄alkylene) is phenylenedimethylene.

Where the radicals Rn, R₁₂ and R₁₃, together with the nitrogen atoms to which they are attached, form a 5- to 10-membered heterocyclic ring, the resulting ring is for example

A 6-membered heterocyclic ring is preferred.

Where the radicals R₁₄ and R₁₅, together with the nitrogen atom to which they are attached, form a 5- to 10-membered heterocyclic ring, the resulting ring is for example 1-pyrrolidyl, piperidino, morpholino, 1-piperazinyl, 4-methyl-1 -piperazinyl, 1-hexahydroazepinyl, 5,5,7- trimethyl-1-homopiperazinyl or 4,5,5,7-tetramethyl-1-homopiperazinyl. Morpholino is particularly preferred.

n₂ is preferably 2-25. n₃ is preferably 2-25, especially 2-20 or 2-10. n₇ is preferably 1-25, especially 1-20 or 1-10.

Particularly preferred are the oxoammonium salts wherein in formula (I) ^ is 2 and R₂ is C₂-Cιoalkylene;

in formula (II) R₃ and R₇are hydrogen,

R , R₅ and R₆ independently of one another are C₂-C₆alkylene,

R₈ is hydrogen or d-C₆alkyl; and

X,-X₈ are groups of the formula (IV); in formula (V) R₉ is d-C₁₂alkyl, preferably n-butyl;

in formula (VI) Rn, R₁₃, Ru and R₁₅ independently of one another are hydrogen, Cι-C₈alkyl,

C-₅-Cacycloalkyl, methyl-substituted C₅-C₈cycloalkyl, phenyl, C₇-C₉phenylalkyl or a group of the formula (IV), or the radicals R₁₄ and Rι₅, together with the nitrogen atom to which they are attached, form a

6-membered heterocyclic ring,

R₁₂ is QrCioalkylene, and n₂ is a number from 2 to 25;

in formula (VII) R₁₆ is C C alkyl, C₅-C₈cycloalkyl or phenyl, R₁₇ is C₃-C₆alkylene, and n₃ is a number from 2 to 25;

in formula (VIM) R₁₈ is d-Cι₂alkyl, preferably n-butyl;

in formula (IX) the residue -NR₁₉R₂₀ is

In formula (X) R₂₁ is tert. C₈H₁₇

ι formula (XI) R₂.

in formula (XII) the radicals R₃₃ independently of one another are hydrogen or C_rC₄alkyl, and the radicals R₃₄ and R₃₅ independently of one another are C₁-C₄alkyl; and in formula (XIII) the radicals R_3β, Rββ, R₃₉ and R ₀ independently of one another are

Cι-C₄alkylene,

R₃₇ is a direct bond, and n₇ is a number from 1 to 25.

Special prefernec is given to oxoammonium salts wherein in formula (IX) Rι₉ is hydrogen, R₂₀ is tert. C₈Hι₇ and t is 6.

Because of the solubility characteristics (insolubility) the compounds of the formula (IX) derived from CHIMASSORB 966 are especially preferred.

Preparation of the amine compounds

The products described under a) to k) above, wherein Z is NH can be prepared using 2,2,6,6-tetramethylpiperidine derivatives as starting compounds. The 2,2,6,6-tetramethyl- piperidine derivatives are essentially known (some are commercially available) and can be prepared by known methods, for example as described in US-A-3,640,928, US-A-4, 108,829, US-A-3,925,376, US-A-4,086,204, EP-A-782,994, EP-A-850,938, US-A-4,331 ,586, US-A-5,051 ,458, US-A-4,477,615 and Chemical Abstracts - CAS No. 136504-96-6, US-A-4,857,595, DD-A-262,439 (Derwent 89-122983/17, Chemical Abstracts 111 :58964u), WO-A-94/12,544 (Derwent 94-177274/22), GB-A-2,269,819, US-A-4,340,534, EP-A-172,413, US-A-4,529,760, US-A-5, 182,390 (Chemical Abstracts CAS No. 144923-25-1), US-A-4,976,889, SU-A-768,175 (Derwent 88-138,751/20), US-A-4,769,457 and DE-A-2,748,362 (Derwent 35517B/19).

Amine compounds having a triazine moiety can be prepared by reacting 2,4,6-trichloro-1 ,3,5- triazine (cyanuric chloride) with alkyl-(2,2,6,6-tetramethyl-piperidin-4-yl)-amine and oxidizing the reaction product obtained as described, for example, in US 4,442,250 (Chimosa Chimica Organica SpA).

Further examples are given in US 6,441 ,166. For example a 2,2,6,6, tetramethyl-4- piperidinyl) derivative such as N-(2,2,6,6-tetramethyl-4-piperidinyl)-n-butylamine is slowly added at 0°C to a solution of cyanuric chloride in of xylene, keeping the temperature during the addition and for further 1 hour. Preparation of the oxoammonium compounds of the formulae l-XII

The synthesis of the oxoammonium salt can be carried out starting from the corresponding amine derivative (A) according to the following scheme:

(A) (B) (C)

The oxidation to the nitroxyl derivative (B) can be carried out in a two phase medium according to the method described in WO00/40550.

Suitable oxidizing agents are: peracetic acid, m-chloroperoxybenzoic acid (m-CBPA), hydrogen peroxide, alkyl hydroperoxide, oxygen + metal.

The nitroxyl derivative (B) is reacted with bromine, chlorine, fluorine or jodine, preferably chlorine to give the oxoammonium salt (C).

Alternatively, the synthesis of the oxoammonium salt can be carried out starting from the corresponding exhausted hydroxylamine salt according to the following scheme:

A suitable base is selected from sodium hydroxide, potassium hydroxide, potassium carbonate and the like.

Suitable oxidizing agents are the same as mentioned above.

X is bromine, chlorine, fluorine or jodine, preferably chlorine.

A preferred compound of formula I can be prepared starting from TINUVIN 770 commercially available from Ciba Specialty Chemicals.

TINUVIN 770 is a compound of the formula I, with Z = NH, n = 2 and R₂ = octylene. A preferred compound of the formula II can be prepared starting from CHIMASSORB 119 commercially available from Ciba Specialty Chemicals.

CHIMASSORB 119 is a compound of the formula II, with X^Xa = formula IV, with Z = NH and R₃ = n-butyl, R and R₆ = propylene, R₅ = ethylene.

A preferred compound of the formula IX can be prepared starting from CHIMASSORB 966 commercially available from Ciba Specialty Chemicals.

CHIMASSORB 966 is a compound of the formula IX, with Xn = formula IV, Z = NH; R₁₉ = H and R₂₀ = tert. C₈H₁₇, t = 6.

A preferred compound of the formula X can be prepared starting from CHIMASSORB 944 commercially available from Ciba Specialty Chemicals.

CHIMASSORB 944 is a compound of the formula X, with Xι₂ = formula IV Z = NH and R_2i= tert. C₈H₁₇, t = 6.

A preferred compound of the formula XI can be prepared starting from CHIMASSORB 2020 commercially available from Ciba Specialty Chemicals.

CHIMASSORB 2020 is a compound of the formula XI, with X₁₃ = formula IV ,Z = NH, R₂₂, R₂₃ and R₂ = n-butyl, t =6.

Oxoammonium salts according to the invention are used as oxidizing reagent in order to transform the R₁R₂CHOH alcohol group to the corresponding R^CO carbonylic group (Scheme A) or to transform the RιCH₂OH alcohol group to the corresponding RiCHO aldehyde group (Scheme B).

Scheme A

Scheme B

A possible process for the alcohol oxidation is depicted in the following Scheme C, wherein the alcohol optionally dissolved in an organic solvent is passed through a cartridge containing the oxoammonium salt. After the oxidation reaction the exhausted oxoammonium salt can be regenerated.

Scheme C

1 ) Alcohol oxidation 2) Oxoammonium salt Regeneration Peracetic Acid optional Base

A= oxoammonium salt B = hydroxyl-amine.HX salt A* = regenerated oxoammonium salt

Note: the column packed with A^* is re-used for the alcohol oxidation Thus, a further object of the invention relates to a process for the selective oxidation of primary alcohols to aldehydes or of secondary alcohols to ketones in an organic medium without a water phase, which process comprises reacting the alcohol with an oxoammonium salt as defined above or mixtures thereof optionally in an organic solvent.

The alcohol, optionally dissolved in an organic solvent is fed into a reaction vessel and contacted with the oxoammonium salt under stirring.

In a preferred embodiment the aldehyde or ketone is continuously produced. The alcohol, optionally dissolved in an organic solvent is passed through a reaction column packed with the oxoammonium salt (preferably in a cartridge). The product mixture containing the aldehyde or the ketone compound is collected. The aldehyde or ketone is separated by distillation, precipitation or via a standard synthetic organic procedure known by a person skilled in the art. The solvent is fed back into the reaction column.

The alcohol to be oxidized may be water soluble or water insoluble.

As used herein, the term "alcohol" refers to a broad class of hydroxyl-containing organic compounds. Alcohols include prim, and sec. alcohols, monohydric, dihydric, trihydric, and polyhydric alcohols. The term "monohydric alcohols" refers to the radical R-OH where R is alkyl, alkenyl, alkynyl, Ar, heteroaryl, heterocycloalkyl, or cycloalkyl. Examples of alcohols include ethanol, propanol, butanol, octanol, cyclohexanol, phenol and the like. Also suitable compounds having an OH-group are hydroxy amino acids or esters such as, for example, N- protected hydroxyproline methyl ester.

Examples of dihydroxy alcohols include 1 ,2-diols such as for example ethylene glycol, propane-1,2-diol, 2-ethyl-2-butyl propanediol, butane-1 ,2-diol; diols such as for example 1 ,3- propane diol, 1 ,4-butane diol, longer chain α,β-C₅-Cι₈alkyldiols or α,co-C₅-C₁₈alkyldiols such as, for example, pentane diols, hexane diols, octane diols, dodecane diol, diethylene glykol, triethylenglykol, polyethylene glycol, polypropylene glycol, cyclic diols such as 1 ,3-cyclo- pentane diol, 1 ,2-, 1 ,3- or 1 ,4-cyclohexane diol, and the like.

Examples of polyhydroxy alcohols include glycerol, trimethylol ethane, trimethylol propane, trimethylol butane, pentaerythritol, dipentaerythritol, sorbitol, sugar, starch, and the like. The polyol may be polymeric such as, for example, starch or pulp.

Included are also molecules containing other functional groups besides hydroxy such as, for example =O, carboxylic acid, NO₂, unsaturated bond and the like.

Suitable organic solvents are those solvents wherein the oxidizing agent is insoluble, such as e.g. hexane, benzene, toluene, xylene, dichloromethane, cyclohexane, octane, dodecane and the like.

Preferably the oxidizing agent is added in a molar ratio with respect to the alcohol used of from 4:1 to 1:1 more preferably from 2:1 to 1:1 and most preferably in a stδchiometric amount.

The alcohol to be oxidized may be liquid or solid. In the case of liquid alcohols, the reaction can be carried out without the addition of further solvents, but it can be advantageous to carry out the oxidation in a higher dilution. Solid alcohols always require a suitable organic solvent as described above.

Preferably the process is carried out at a temperature of less than 50°C, more preferably at a temperature between 5° C and 30° C

Recvclisation of the exhausted oxoammonium salt

During the oxidation process the oxoammonium salt is reduced to a hydroxyl-amine salt. The oxoammonium salt as well as the hydroxylamine salt are insoluble in the organic solvent. Therefore it is possible to separate the exhausted oxidizing agent containing the hydroxyl amine salt simply by filtration. The regeneration of the oxidizing agent is carried out according to the following Scheme.

The regeneration method comprises the steps of: a) separating the exhausted oxoammonium salt containing the hydroxylamine salt by filtration b) taking up the hydroxylamine salt in a solvent; c) treating the reaction mixture of step b) with a base and an oxidizing agent at a temperature range from -10 to 50°C (preferred 0-25°C) d) separating the organic phase from the water phase e) treating the organic reaction mixture of step d), containing the nitroxyl derivative, with an oxidizing agent at a temperature range from -10 to 50 °C (preferred 0-25°C) f) separating the oxoammonium salt by filtration.

The oxidizing agents are preferably chlorine or bromine.

A further aspect of the invention is the use of an oxoamonium compound as described above for the selective oxidation of primary or secondary alcohols to aldehydes or ketones in an organic medium.

The following examples illustrate the invention. Examples

1. Examples for preparing oxoammonium salts:

Example 1.1 : Oxoammonium chloride salt

Example 1.1.1 : Synthesis of the compound of formula IX (CHIMASSORB 966 derivative):

In a 100 ml autoclave 10 g of the nitroxyl compound A having the structure reported below and 100 ml of dichloromethane are added. The mixture is cooled at 5-15°C and under vigorous stirring pure chlorine gas is added slowly over about 2 h; after that the temperature is allowed to raise to 25°C and the reaction is continued for additional 10 h at 25-30°C. Then the crude precipitated product is separated from the mixture by means of a filtration. The solid precipitated is washed four times with dichloromethane. The so obtained product is dried under vacuum; obtaining a purple colored solid in a quantitative yield.

Structure of the nitroxyl compound A:

Example 1.1.2: Svnthesis of the compound of formula V:

Following the procedure of Example 1.1.1 and using as starting material the nitroxyl compound B having the structure reported below (procedure claimed in WO 00/40550), the corresponding oxoammonium chloride salt is obtained. Structure of the nitroxyl compound B:

Example 1.1.3: Svnthesis of the compound of formula II (CHIMASSORB 119 derivative):

Following the procedure of Example 1.1.1 and using as starting material the nitroxyl compound C having the structure reported below (procedure claimed in WO 00/40550), the corresponding oxoammonium chloride salt is obtained.

Structure of the nitroxyl compound C:

Example 1.2: Oxoammonium bromide salt Example 1.2.1 : Svnthesis of the compound of formula IX (CHIMASSORB 966 derivative):

In a three-necked flask 15 g of the nitroxyl compound A having the structure cited in the above example 1.1.1 and 100 ml of toluene are added. The mixture is cooled at 10°C and under stirring it is added dropwise 3.9 g of bromine, which is dissolved in 20ml of toluene; after that the temperature is allowed rising to 25°C and the reaction is continued for additional 10 h at 25-30°C. Then the crude product is filtered off and washed four times with toluene. The so obtained product is dried under vacuum; obtaining a brown colored solid in a quantitative yield, having the following analytical data: % of Ionic Bromide (estimated by Titration): 22% (20% theoretical)

Example 1.2.2: Svnthesis of the compound of formula X (CHIMASSORB 944 derivative)

Following the procedure of Example 1.2.1 and using as starting material the nitroxyl derivative of the CHIMASSORB 944 (procedure claimed in WO 00/40550), the corresponding oxoammonium bromide salt is obtained.

2. Examples for the use of the oxoammonium salts as oxidizing agent.

Example 2.1 : Oxidation of 2-octanol

In a three-necked flask 16.9 g (10.7 mmol) of the freshly obtained product of the example 1.2.1 , 3.7 g (28.6 mmol) of 2-octanol and 210 ml of toluene are added at room temperature; the heterogeneous mixture is maintained while stirring over 16 h; after that the crude organic layer is analyzed using GC: 65.7 % of 2-octanone is detected as only product. (Note: after 65 h the conversion was 100% of the desired product).

Example 2.2: Oxidation of 2-octanol using stored^* oxoammonium salts as oxidizing agents

^* storing conditions: at room temperature in air.

The alcohol oxidation reactions are performed following the general procedure of the example 2.1.

These data confirm the stability of the oxoammonium halogen salt.

3. Recovery and recycle of the exhausted oxoammonium salt

Example 3.1: Recovery of the exhausted oxoammonium salt

OH

⁺R^R1

Oxoammonium salt derivative Hydroxyl amine . HX derivative

X= Cl, Br, F, I

Recovery Procedure:

The organic layer of the reaction mixture described at the Example 2.1 is separated from the insoluble product by filtration; then the insoluble solid is recovered and dried under vacuum; obtaining a white product corresponding to the HX salt of the hydroxylamine.

Example 3.2 Re-use of the oxoammonium salt as oxidizing agent recovered from the hydroxylamine HX salt

Example 3.2.1 : Svnthesis of the nitroxyl from the corresponding HX hydroxylamine derivative

K-CO₃

Peracetic Acid Hydroxyl amine . HX derivative Nitroxyl derivative

T=20°C solvent

X= Cl, Br, F, I

In an organic solvent the isolated HX.hydroxyl amine of the example 3.1 is added. Then, at room temperature, 3.45 equivalent of Potassium Carbonate and 2.4 equivalent of peracetic acid (35% sol. in acetic acid) for each HX.hydroxyl amine moiety are added. The mixture is maintained while stirring for 2 h, then the insoluble nitroxyl derivative is filtered off from the reaction mixture and after drying under vacuum, a red colored product is recovered in a quantitative yield.

Example 3.2.2: Svnthesis of the oxoammonium salts from the recovered nitroxyl derivatives of the example 3.2.1

X₂

Recovered Nitroxyl derivative *• Oxoammonium halogen salt

X_g — CI-, Br₂, r₂, l₂

Procedure: following the procedure of the example 1.1.1 or of the example 1.2.1 the recovered nitroxyls of the example 3.2 are transformed in the corresponding chloride and bromide oxoammonium salts.

Example 3.2.3: Use of the recovered oxoammonium salt as oxidizing agent Procedure: following the oxidation procedure of the example 2.1 the recovered oxoammonium salt of the example 3.2.2 is used as oxidizing agent for the oxidation of 2- octanol to the corresponding 2-octanone.

Claims

1. Oxoammonium salts of monomeric or polymeric hindered amines containing at least two structural elements of formula (A)

wherein

Z is -NH, -NOH, -NO° or -N⁺=O X^" with the proviso that at least one of Z is -N⁺=O X^" with X being Cl, Br, F, J; and ^* denotes a valence.

2. Oxoammonium salts according to claim 1 of the formulae I, II, V-XIII a) a of the formula (I)

in which

R₂ is Cι-C₁₄alkylene or bis{(C₁-C₂₀alkyl)oxycarbonyl}C₄-Cιoalkanetetrayl (if ^ is 2), and R₂ is C -C₁₀alkanetetrayl (if ^ is 4);

b) of the formula (II)

in which R₃ and R₇ independently of one another are hydrogen or d-Cι₂alkyl;

R₄, R₅ and R₆ independently of one another are C₂-C₁₀alkylene; and

Xi, X₂. X₃. X4. X5. Xβ. X7 and X₈ independently of one another are a group of the formula (III) or (IV)

in which

Z is -NH, -NOH, -NO⁰ or -N⁺=O X- with the proviso that at least one of Z is -N⁺=O X^" with X being Cl, Br, F, J; R₈ is hydrogen, d-C₁₂alkyl, C₅-C₁₂cycloalkyl, C C₄alkyl-substituted C₅-C₁₂cycloalkyl, phenyl, -OH- and/or d-Cι₀alkyl-substituted phenyl, C₇-C₉phenylalkyl, C₇-C₉phenylalkyl which is substituted on the phenyl radical by -OH and/or d-Cι₀alkyl; or a group of the formula (IV);

c) of the formula (V)

in which

R₉ is hydrogen, C,-C₁₂alkyl, C₃-C₁₂cycloalkyl or phenyl;

is a group of the formula (IV) (IV)

in which

Z is -NH, -NOH, -NO⁰ or -N⁺=O X^" with the proviso that at least one of Z is -N⁺=O X^" with X being Cl, Br, F, J;

d) of the formula (VI)

in which

Rn. i₃, R₁₄ and Rι₅ independently of one another are hydrogen, d-C₁₂alkyl, C₅-C₁₂cyclo- alkyl, C₁-C₄alkyl-substituted C₅-C₁₂cycloalkyl, phenyl, -OH- and/or d-C₁₀alkyl- substituted phenyl, C₇-C₉phenylalkyl, C₇-C₉phenylalkyl which is substituted on the phenyl radical by -OH and/or Ci-Cioalkyl; or a group of the formula (IV) as defined under b); R₁₂ is C₂-Cι₈alkylene, C₅-C₇cycloalkylene or d-C₄alkylenedi(C₅-C₇cycloalkylene), or the radicals Rn, Rι₂ and Rι₃, together with the nitrogen atoms to which they are attached, form a 5- to 10-membered heterocyclic ring; or R₁₄ and R₁₅, together with the nitrogen atom to which they are attached, form a 5- to

10-membered heterocyclic ring; n₂ is a number from 2 to 50, and at least one of the radicals Rn, R₁3, R₁4 and R₁₅ is a group of the formula (IV)

(IV) in which

Z is -NH, -NOH, -NO° or -N⁺=O X^" with the proviso that at least one of Z is

-N⁺=O X^" with X being Cl, Br, F, J

e) of the formula (VII)

in which Z is -NH, -NOH, -NO⁰ or -N⁺=O X^" with the proviso that at least one of Z is -N⁺=O X^' with X being Cl, Br, F, J; R₁₆ is d-Cι₀alkyl, C₅-Cι₂cycloalkyl, d-C₄alkyl-substituted C₅-C₁₂cycloalkyl, phenyl or

Ci-Ci₀alkyl-substituted phenyl; R₁₇ is C₃-C₁₀alkylene; n₃ is a number from 2 to 50;

f) of the formula (VIM)

Λ10 is a group of the formula (IV) (IV)

in which

Z is -NH, -NOH, -NO⁰ or -N⁺=O X- with the proviso that at least one of Z is -N⁺=O X- with X being Cl, Br, F, J;

g) of the formula (IX)

in which t is a number from 2 to 18; R₁₉and R₂₀ independently of one another are hydrogen, d-C₁₂alkyl, C₅-C₁₂cycloalkyl or phenyl or a group of the formula (II) or (IV); or

Xn is a group of the formula (IV) (IV)

in which

h) of the formula (X)

R₂ι is hydrogen, d-Cι₂alkyl, C₃-C₁₂cycloalkyl or phenyl;

X₁₂ is a group of the formula (IV) (IV)

in which

i) of the formula (XI)

R₂₂ and R₂₃ independentliy of one another are hydrogen, Cι-C₁₂alkyl, C₅-C₁₂cycloalkyl or phenyl or a group of the formula (III) or(IV); or R₂₂ and R₂₃, together with the nitrogen atom to which they are attached, form a 5- to

10-membered heterocyclic ring which may be further interrupted by an O-atom; R₂₄ is hydrogen, d-C₁₂alkyl, C₅-d₂cycloalkyl or phenyl;

X₁₃ is a group of the formula (IV) (IV)

in which

Z is -NH, -NOH, -NO° or -N⁺=O X^" with the proviso that at least one of Z is -N⁺=0 X^" with X being Cl, Br, F, J;

j) of the formula (XII)

'33 ,'35 ,'33

X₁₄ N C C N X₁₄

^R34 (XII) in which

R₃₃ independently of one another are hydrogen, d-C₁₂alkyl or d-C₁₂acyl, and

R₃₄ and R₃₅ independently of one another are Cι-Cι₂alkyl; X₁₄ is a group of the formula (IV) (IV)

in which

k) of the formula (XIII)

(XIII) R36. R37, R38. R39 and R ₀ independently of one another are a direct bond or d-C₁₀alkylene, and n₇ is a number from 1 to 50;

X₁₅ is a group of the formula (IV) (IV)

in which

Z is -NH, -NOH, -NO⁰ or -N⁺=O X^" with the proviso that at least one of Z is -N⁺=O X^" with X being Cl, Br, F, J.

3. Oxoammonium salts according to claim 2, wherein in formula (I) n^ is 2 and R₂ is C₂-C₁₀alkylene;

in formula (II) R₃ and R₇ are hydrogen,

R , R₅ and R₆ independently of one another are C₂-C₆alkylene,

R₈ is hydrogen or d-C₆alkyl; and

XrXβ are groups of the formula (IV); in formula (V) R₉ is d-C^alkyl, preferably n-butyl;

in formula (VI) Rn, R₁₃, Rι₄ and R ₅ independently of one another are hydrogen, d-C₈alkyl,

C₅-C₈cycloalkyl, methyl-substituted C₅-C₈cycloalkyl, phenyl, C₇-C₉phenylalkyl or a group of the formula (IV), or the radicals Rι₄ and R₁₅, together with the nitrogen atom to which they are attached, form a

6-membered heterocyclic ring,

R₁₂ is C₂-C₁₀alkylene, and n₂ is a number from 2 to 25;

in formula (VII) R₁₆ is d-C₄alkyl, C₅-C₈cycloalkyl or phenyl, R₁₇ is C₃-C₆alkylene, and n₃ is a number from 2 to 25;

in formula (VIII) R₁₈ is C_rC₁₂alkyl, preferably n-butyl;

in formula (IX) the residue -NR₁₉R₂₀ is

In formula (X) R₂₁ is tert. C₈H₁₇

in formula (XI) R₂₄ is Cr ^■C₁₂ alkyl and the residue ^■ -NR22R23 is

In formula (XII) the radicals R₃₃ independently of one another are hydrogen or d-C₄alkyl, and the radicals R₃₄ and R₃₅ independently of one another are Cι-C alkyl; ln formula (XIII) the radicals R_3β, R₃₈, R₃₉ and R₄₀ independently of one another are d-C₄alkylene,

R₃₇ is a direct bond, and n₇ is a number from 1 to 25.

4. Oxoammonium salts according to claim 3, wherein in formula (IX) R₁₉ is hydrogen, R₂₀ is tert. C₈H_i7 and t is 6.

5. A process for the selective oxidation of primary alcohols to aldehydes or of secondary alcohols to ketones in an organic medium without a water phase, which process comprises reacting the alcohol with an oxoammonium salt according to claim 1 or mixtures thereof optionally in an organic solvent.

6. A process according to claim 5, whereby the aldehyde or keton is continuously produced, which process comprises a) passing the alcohol dissolved in an organic solvent through a reaction column, b) collecting the product mixture containing the aldehyde or the ketone compound; c) separating the aldehyde or ketone, d) feding back the solvent into the top of the reaction column, e) regenerating the exhausted oxoammonium salt.

7. A process according to claim 5 or 6, wherein the molar ratio of oxidizing agent to alcohol is from 4:1 to 1:1.

8. A process according to claim 5 or 6, which process is carried out at a temperature of less than 50°C.

9. A process according to claim 5 or 6, wherein the regeneration process comprises the steps of: a) separating the exhausted oxoammonium salt containing the hydroxylamine salt by filtration, b) taking up the hydroxylamine salt in a solvent, c) treating the reaction mixture of step b) with a base and an oxidizing agent at a temperature range from -10 to 50°C, d) separating the organic phase from the water phase, e) treating the organic reaction mixture of step d), containing the nitroxyl derivative, with an oxidizing agent at a temperature range from -10 to 50 °C, f) separating the oxoammonium salt by filtration.

10. Use of an oxoamonium compound according to claim 1 for the selective oxidation of primary or secondary alcohols to aldehydes or ketones in an organic medium.