Process for the oxidation of alcohols using homogeneously...

Details Process for the oxidation of alcohols using homogeneously... Process for the oxidation of alcohols using homogeneously...

2001-06-14

2002-09-17

Pezzuto, Helen L. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S258000, C526S312000, C526S328500, C526S332000

Reexamination Certificate

active

06451943

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed at a process for the oxidation of alcohols using homogeneously soluble polymer-enlarged nitrogen compounds as catalysts. In particular, the invention relates to a process where the catalysts used are compounds that can be obtained by polymerization of a mixture containing
(i): 0.1-100, preferably 1-20 wt. -% of a compound (I)
(ii): 0-99.9, preferably 80-99 wt. -% (meth)acrylic acid ester,
(iii): 0-80, preferably 1-20 wt. -% other &agr;,&bgr;-unsaturated compounds, other than i) wherein A is a ring with 5 to 8 elements, which in addition to one nitrogen can have 0-3 other hetero atoms, such as N, O, S, and which in addition to the substituents shown in the formula can have 0-3 other radicals, such as (C
1
-C
8
)-alkyl, (C
1
-C
8
)-alkoxy, halogens, wherein R
1
, R
2
, R
3
, R
4
are, independent of each other, (C
1
-C
8
)-alkyl, (C
6
-C
18
)-aryl, (C
7
-C
19
)-aralkyl, (C
3
-C
8
)-cycloalkyl, or R
1
and R
2
and/or R
3
and R
4
or R
1
and R
3
and/or R
2
and R
4
are connected with one another via a (C
2
-C
8
)-alkylene bridge, wherein R
5
is H or methyl, X is O, NH, NR
1
, and wherein Y is · or H, such as HEMA or EGDMA. It is understood that all subranges and numbers within the above discussed ranges are present as if explicitly written out.
In organic synthesis, the oxidation of alcohols represents an important transformation for obtaining aldehydes, ketones, or acids. These in turn are advantageously suitable, if they are not themselves intended as the target molecule, for further reaction to produce successor products, since they are very easily accessible to nucleophilic addition reactions. They therefore frequently play a key role specifically in the technical production of bioactive molecules, as part of the synthesis path.
The oxidation of secondary and primary alcohols to produce aldehydes and ketones with N-oxygen compounds of 2,2,6,6-tetramethyl-4-piperidine (TEMPO) in the presence of oxidants such as m-CPBA, hypochlorite/bromite solution, or K
3
Fe(CN)
6
has been known for a long time (J. Org. Chem. 1987, 52, 2559-62; ibid. 1975, 40, 1860; Synthesis 1966, 1153). Furthermore, polymer-enlarged TEMPO radicals already have been synthesized with the purpose of working them into polymer mixtures as UV stabilizers (DE 2748362; L. Wenzhong, Polym. Degra. and Stab. 1991, 31, 353-364).
Endo et al. used partially soluble polymer-enlarged TEMPO compounds in alcohol oxidation reactions, among other substances (Journal of Polymer Science: Polymer Chemistry Edition, Vol. 23, 2487-94 (1985)). However, it was shown that the insoluble oxidation catalysts of the type introduced there were better.
An object of the present invention is to provide a process for the oxidation of alcohols in the presence of oxidation catalysts, on the basis of homogeneously soluble polymer-enlarged nitrogen compounds. In particular, this process is usable on a technical scale, in other words advantageous with regard to the aspects of economics and ecology.
Because an oxidation agent and catalytic amounts of homogeneously soluble polymer-enlarged nitroxyl derivatives are used in a process for the oxidation of alcohols, where these derivatives are obtained by copolymerization of a mixture containing
(i): 0.1-100, preferably 1-20 wt. -%, including 3, 5, 10 and 15 wt. % and all weights percent between all stated values of a compound (I)
where Y═·or H,
A is a ring with 5 to 8 elements, which in addition to one nitrogen can have 0-3 other hetero atoms, such as N, O, S, and which in addition to the substituents shown in the formula can have 0-3 other radicals, such as (C
1
-C
8
)-alkyl, (C
1
-C
8
)-alkoxy, halogens, R
1
, R
2
, R
3
, R
4
are, independent of each other, (C
1
-C
8
)-alkyl, (C
6
-C
18
)-aryl, (C
7
-C
19
)-aralkyl, (C
3
-C
8
)-cycloalkyl, or R
1
and R
2
and/or R
3
and R
4
or R
1
and R
3
and/or R
2
and R
4
are connected with one another via a (C
2
-C
8
)-alkylene bridge, R
5
is H or methyl, X is O, NH, NR
1
, and wherein Y is the 0-3 other radicals or H.
(ii): 0-99.9, including 5, 10, 20, 30, 40, 50, 60, 70, 80, and 90 and all weights percent between all stated values, preferably 80-99 wt. -% (meth)acrylic acid ester,
(iii): 0-80, including 5, 10, 20, 30, 40, 50, 60 and 70 and all weights percent between all stated values, preferably 1-20 wt. -% other &agr;,&bgr;-unsaturated compounds, such as HEMA or EGDMA, the desired alcohol oxidation products, preferably the aldehydes and ketones, are obtained in a surprisingly simple and cost-effective manner. According to the invention, the oxidation reaction is completed within a few minutes, and the mixture can be processed. The catalyst can be removed and reused, and the yields of oxidation product are almost quantitative. Because the catalyst can be reused, the synthesis costs can be kept low.
It is understood that · signifies a radical electron in the context of this invention.
In a preferred embodiment, the radicals R
1
−R
4
═methyl, R
5
═methyl or H, X═O, NH, where A represents a piperidine ring.
A process where the polymer-enlarged nitroxyl derivative with the formula (II)
with a ratio of n/m of 1-100, preferably 1-50, and an average molecular weight of 1-200 kDa, preferably 10-100 kDa, is used, is especially preferred.
Other &agr;,&bgr;-unsaturated compounds of Type iii that can be used are particularly those monomers that help to change the solubility properties of the polymer, i.e. ideally adapt it to the solvent system to be used. These monomers furthermore can have a crosslinking effect. This has the result that individual polymer strands are connected with one another, which in turn can have a significant influence on the solubility properties and the secondary structure of the polymer backbone and thereby indirectly on the reactivity of the catalyst. Other compounds that can be used are preferably the monomers of component i) and ii) of the polymerizate iii) in DE 19734360. The use of HEMA or EGDMA is very especially preferred in this regard.
In principle, the substances that a person skilled in the art would consider for use for this reaction can be used as oxidation agents. Preferably, these are K
3
Fe(CN)
3
or aqueous NaOCl solution. Aqueous NaOCl solution is preferred, since it is less expensive and does not result in any cyanide problems, especially on a large technical scale.
The oxidation according to the invention is fundamentally conducted in accordance with that using monomer TEMPO, preferably in a two-phase system of organic and aqueous solvents. Ethyl acetate, acetonitrile, dichloromethane, or benzonitrile can serve as preferred organic solvents. Ethyl acetate and acetonitrile are very especially preferred.
The oxidation agent, the polymer-enlarged nitroxyl derivative of Formula (I), preferably that of Formula (II), is dissolved in the selected two-phase system. In the aqueous phase, the pH is adjusted in such a way that oxidation takes place at a pH of 6-13, preferably 9-10. Preferably, sodium carbonate is used to adjust the pH. However, any of the bases that a person skilled in the art would use for this purpose can be used, such as potassium carbonate, sodium hydrogen carbonate, sodium hydrogen phosphate, for example. Subsequently, the alcohol can be added to the mixture. The reaction is quantitatively completed in a few minutes.
The reaction is preferably carried out at temperatures from −20° C.-80° C., preferably 0-30° C. After completion of the reaction, it can be processed using methods known to a person skilled in the art.
If work is carried out using a two-phase system, the phase that contains organic product and possibly catalyst is separated from the aqueous phase. A special advantage of the process according to the invention is that the polymer-enlarged catalyst can easily be recovered from the organic phase after the reaction is complete, and is therefore available for another oxidation cycle. This can be done using filtration by means of an ultrafiltration
anofiltration membrane, or

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