Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2002-05-23
2003-05-20
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S902000, C568S909000
Reexamination Certificate
active
06566564
ABSTRACT:
This application is a 371 of PCT/EP00/11580, filed Nov. 21, 2000.
The present invention relates to an improved process for the isomerization of precursor allyl alcohols to product allyl alcohols in both directions of the equilibrium in the presence of tungsten oxo(VI) complexes comprising additional nitrogen-containing ligands.
Allyl alcohols are important intermediates in industrial organic chemistry. Tertiary allyl alcohols in particular are used, for example, as intermediates in the preparation of fragrances and also as additives in soaps or detergents.
It is known that allyl alcohols isomerize under acidic catalysis. This isomerization corresponds to a 1,3-migration of the hydroxyl group and a corresponding shift of the double bond, as shown in the equation below with the formulae I and II:
in which R
1
to R
5
are hydrogen or hydrocarbon radicals.
The process is particularly suitable for the preparation of tertiary product allyl alcohols, such as 2-linalool, by isomerization of primary or secondary allyl alcohols, such as geraniol and nerol.
Geraniol (2-trans-3,7-dimethyl-2,6-octadien-8-ol), nerol (2-cis-3,7-dimethyl-2,6-octadien-8-ol) and 2-linalool (3,7-dimethyl-1,6-octadien-3-ol) are important compounds in the fragrance industry. They are used either directly as fragrances, or are converted into higher molecular weight fragrances by reaction with other compounds. These terpene alcohols are also important as C
10
building blocks in the synthesis of vitamins, such as vitamin E.
In the past, preference has been given in the literature to the description of processes for the isomerization of linalool to geraniol. Since the isomerizations are equilibrium reactions, the processes developed can, in principle, also be used for the reverse reaction of the isomerization of geraniol or nerol to linalool.
Initially, the isomerization reactions of allyl alcohols were carried out using acids as catalysts. However, these processes were of only limited importance since during them secondary reactions, such as, for example, dehydrations or cyclizations, predominate.
Later, the catalytic rearrangement of substituted allyl alcohols using molybdenum, vanadium and tungsten catalysts was investigated (cf. P. Chabardes et al in Tetrahedron 33 (1977), pages 1775-1783.).
Whereas the molybdenum compound described in GB 1 256 184 as isomerization catalyst produced unsatisfactory reaction results, using tungsten oxo(VI) alkoxide catalysts of the formula WO(OR)
4
in the presence of a nitrogen base as additional ligand, relatively high selectivities coupled with simultaneously higher activities, compared with the analogous vanadium oxo(V) alkoxide catalysts of the formula VO(OR)
3
, were possible. Further advantages of the tungsten catalysts are that they can be readily separated off from the reaction mixture (cf. T. Hosogai et al. in
Chemistry Letters
1982, pages 357-360) and that they have only low toxicity compared with the vanadium catalyst.
Furthermore, DE 25 16 698 discloses the preparation of novel catalysts based on tungsten, and to the use thereof for the catalytic rearrangement of tertiary to primary allyl alcohols. In this process, the catalysts described are tungsten oxo(VI) complexes comprising alkoxy radicals and/or trialkylsilyl radicals bonded via oxygen, which, to improve the selectivity, additionally comprise ligands bonded coordinately to the tungsten, which comprise an element chosen from the elements N, P, As and Bi, in particular ligands chosen from the class of primary, secondary and tertiary monoamines, of polyamines, of Schiff's bases, of imines, nitriles and isonitriles. Ligands which are cited therein as particularly suitable are primary monoamines, such as methylamine, ethylamine, propylamine, &bgr;-ethoxyethylamine, butylamine, cyclohexylamine, alinine and naphthylamine; secondary monoamines, such as dimethylamine, diethylamine, dibutylamine, dicyclohexylamine, methylaniline, methylcyclohexylamine, piperidine, morpholine and pyrrolidine; tertiary monoamines, such as trimethylamine, triethylamine, ethyldibutylamine, tricyclohexylamine, dimethylaniline, pyridine, picoline, quinoline, isoquinoline, N-methylpyrrolidine and N-methylmorpholine; ethylenediamine, pyrazine, piperazine, pyrimidine, triethylenediamine, 1,8-diazabicyclo[5.4.0]undec-7-ene, polyethyleneimines, and ion exchanger resins having a large number of amino groups within the molecule, in particular pyridine, triethylamine, cyclohexylamine, diethylamine and tricyclohexylphosphine. Aminoalcohols are not mentioned therein. The selectivities for primary alcohols, such as nerol and geraniol, achieved with this process are extremely good, although the conversions achieved are still not ideal.
Our own investigations into the isomerization of geraniol using a 0.05 mol % strength solution of tungsten oxo(VI) tetrakis geranylate analogously to the process described in DE 25 16 698 have shown that the rearrangement to linalool proceeds in a significantly more selective manner in the presence of a nitrogen base at 200° C. (reaction time about 1 hour) than without co-use of a nitrogen base (see Comparatives Examples 1 to 5).
The nitrogen bases used here were diethylamine, pyridine, imidazole and poly(4-vinylpyridine).
Disadvantages of these experiments were the comparatively low conversions coupled with simultaneously high temperatures of more than 150° C., which accelerated the formation of by-products.
It is an object of the present invention to improve the process for the isomerization of allyl alcohols in the presence of tungsten oxo(VI) complexes comprising additional nitrogen-containing ligands at temperatures of from 50 to 300° C. such that, even in the case of the isomerization of primary or secondary allyl alcohols, such as geraniol and nerol, to tertiary allyl alcohols, such as linalool, relatively high conversions of the precursor allyl alcohol used are achieved, as a result of which the rate of the establishment of an equilibrium is accelerated, and the space-time yields increase.
Surprisingly, we have found that the process for the isomerization of precursor allyl alcohols to product allyl alcohols in the presence of homogeneously dissolved tungsten oxo(VI) complexes comprising additional nitrogen-containing ligands gives, coupled with selectivities which remain the same, higher activities for the isomerization of geraniol and nerol to linalool than corresponding isomerizations using tungsten oxo(VI) alkoxide catalysts in the presence of the known nitrogen bases alone if aminoalcohols are used as additional nitrogen-containing ligands.
A higher activity during the allyl rearrangement also results when the amino alcohols are added only subsequently to tungsten oxo(VI) alkoxide catalysts of the formula WO(OR)
4
, to which nitrogen bases have already been added as additional ligands.
Accordingly, the invention provides a process for the isomerization of precursor allyl alcohols to product allyl alcohols in the presence of either preprepared or in-situ-generated tungsten oxo(VI) complexes comprising additional nitrogen-containing ligands at temperatures of from 50 to 300° C., wherein, in the catalyst, as well as the nitrogen bases known as additional nitrogen-containing ligands, or instead of these nitrogen bases, aminoalcohols are present as additional nitrogen-containing ligands.
Examples of allyl alcohols which can be advantageously isomerized using the process according to the invention and which may be mentioned are:
2-Methyl-3-buten-2-ol, prenol (3-methyl-2-buten-1-ol), linalool, nerol and geraniol, and farnesol (3,7,11-trimethyldodeca-2,6,10-trien-1-ol) and nerolidol (3,7,11-trimethyldodeca-1,6,10-trien-3-ol), in particular linalool, nerol and geraniol.
The aminoalcohols which can be used in the process according to the invention are aminoalcohols of the formula III,
in which R
8
and R
9
are identical or different and are hydrogen, C
1
- to C
4
-alkyl, —CH
2
—C
6
H
5
OH; —C
2
H
5
OH or —C
3
H
7
OH,
R
10
and R
11
are identical or different and are H, C
1
- to C
4
-alkyl, or togeth
Ebel Klaus
Stock Frank
Barts Samuel
BASF - Aktiengesellschaft
Keil & Weinkauf
Price Elvis O.
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