Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
1998-09-10
2001-02-06
Padmanabhan, Sreeni (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S361000, C568S408000, C568S409000, C568S415000
Reexamination Certificate
active
06184420
ABSTRACT:
The present invention relates to the preparation of &ggr;,&dgr;-monounsaturated or &bgr;,&ggr;,&dgr;-diunsaturated ketones which are useful fragrances or useful intermediates for the synthesis of natural substances, by the combination of conventional reactions of allyl alcohols or propargyl alcohols with isopropenyl ethers with the formation of ketals of acetone as a byproduct, the isopropenyl ethers being prepared by reacting ketals of acetone with propyne or allene in the gas phase over heterogeneous catalysts and the ketal of acetone, obtained as byproduct, being fed into the stated preparation of the isopropenyl ether.
DE 1 193 490 and R. Marbet and G. Saucy, Helv. Chim. Acta 50, (1967), 2091-2095 and 2095-2100 disclose a process for the preparation of &ggr;,&dgr;-unsaturated ketones by reacting an allyl alcohol with enol ethers, in particular isopropenyl ethers, in the presence of an acid catalyst, e.g. phosphoric acid.
Furthermore, U.S. Pat. No. 3,029,287 and G. Saucy and R. Marbet, Helv. Chim. Acta 50, (1967) 1158-1167 disclose the reaction of the propargyl alcohols with enol ethers in the presence of acid catalysts to give &bgr;,&ggr;,&dgr;-diunsaturated ketones.
In both reactions, one mole of the corresponding ketal is formed as a byproduct from 2 moles of enol ether used, for example acetone dimethyl ketal from isopropenyl methyl ether used, in accordance with the following equations:
In these equations, R
1
to R
5
are each hydrogen or alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl or aralkyl radicals which are unsubstituted or substituted by oxygen-containing groups, it also being possible for R
1
and R
2
, together with the carbon atom to which they are bonded, to form a 5- or 6-membered ring, and R
6
is alkyl of 1 to 4 carbon atoms.
The ketal IV obtained as a byproduct must be converted back into the enol ether III for economic reasons. It is known that this can be done by converting the ketals, either in the liquid phase with acidic catalysts (according to EP 703 211) or in the gas phase over heterogeneous catalysts (according to DE 19 544 450) with elimination of alcohol, into the corresponding enol ethers according to the following equation:
Here, R is hydrogen or alkyl and R
6
has the abovementioned meaning.
The stated known processes permit the preparation of the enol ethers in good yields in some cases but have the following disadvantages:
The reaction in the liquid phase according to EP 703 211 requires the use of a dissolved foreign substance, ie. an organic acid, the removal of which from the reaction mixture requires an additional separation step. Compared with the process in the liquid phase using a homogeneously dissolved catalyst, the process according to DE 19544450 has the advantage of the reaction in the gas phase over a heterogeneous catalyst that requires fairly high temperatures.
Common to both processes is that one mole of alcohol is separated per mole of ketal and has to be separated off in an additional purification step, at considerable expense in some cases, and as a rule has to be discarded. This applies in particular to methanol, which frequently forms azeotropic mixtures. The weight yield, based on the ketal, is thus inevitably reduced.
It is an object of the present invention to provide a combination process which on the one hand permits the preparation of the required enol ether III over a heterogeneous catalyst in good yields without the alcohol originating from the ketal being obtained as a byproduct in stoichiometric amount and, on the other hand, recycling of the ketal obtained in the reactions of equations 1 and 2 into the preparation of the enol ethers.
We have found that this object is achieved, according to the invention, by a process for the preparation of unsaturated ketones of the formulae Ia and Ib
where R
1
, R
2
, R
3
, R
4
and R
5
are each hydrogen or alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl or aralkyl radicals which are substituted or unsubstituted by oxygen-containing groups, it also being possible for R
1
and R
2
together to form a 5- or 6-membered ring, which comprises the combination of the following reactions:
a) The conventional reaction of an allyl alcohol of the formula IIa or a propargyl alcohol of the formula IIb
with an isopropenyl ether of the formula III
where R
6
is alkyl having 1 to 4 carbon atoms, with formation of a ketal of the formula IV
where R
6
has the abovementioned meaning, as a byproduct,
b) preparation of the isopropenyl ether of the formula III by reacting a ketal of the formula IV with propyne or allene, or a mixture thereof in the gas phase at elevated temperatures in the presence of a heterogeneous catalyst containing zinc or cadmium together with silicon or oxygen, and
c) feeding the ketal of the formula iv formed in the reaction (a) into stage (b) for the preparation of the isopropenyl ether of the formula III again.
The reaction of stage (a) is described in detail in the technical literature and is claimed in the present invention not for itself, but in combination with steps (b) and (c):
The conditions in stage (a) are described in DE 1193490 or U.S. Pat. No. 3,029 287 or the stated publications in Helv. Chim. Acta. In this context, the information in these patent publications and literature publications are hereby expressly incorporated by reference.
The conditions in stage (a) are in general not critical for carrying out the novel combination process and can of course also be varied, for example by the choice of the catalyst and, if required, of the starting materials.
Accordingly, more recent improvements of the reaction in stage (a) are of course also suitable, as described, for example, in DE 19 649 564.4.
Preferred starting materials of the formula IIa are in particular tertiary allyl alcohols, R
1
preferably being a saturated or unsaturated, branched or straight-chain alkyl radical which is unsubstituted or substituted by oxygen-containing groups, e.g. methoxy or ethoxy groups, an aryl radical or an alkylaryl radical of up to 20 carbon atoms and R
2
is preferably C
1
-C
4
-alkyl, in particular methyl, it also being possible for R
1
and R
2
together to be tetramethylene or pentamethylene which is unsubstituted or substituted by one or more lower alkyl groups, and R
3
, R
4
and R
5
are each hydrogen.
Specific examples are 3-methyl-1-buten-3-ol, 3,7-dimethyl-1-octen -3-ol (hydrolinalool), 3,7-dimethylocta-2,6-dien-3-ol (linalool), 1-vinylcyclohexanol, 3,7,11-trimethyl-dodeca-1,6,10-trien-3-ol (nerolidol), 3,7,11-trimethyl-dodeca-1,6-dien-3-ol (hydronerolidol) and 3,7,11-trimethyl-dodec-1-en-3-ol(tetrahydronerolidol) and isophytol.
Preferred propargyl alcohols are tertiary propargyl alcohols of the formula IIb where R
1
is a saturated or unsaturated, branched or straight-chain alkyl radical which is unsubstituted or substituted by oxygen-containing groups, or an aryl radical or an alkylaryl radical, each of up to 20 carbon atoms, and R
2
is C
1
-C
4
-alkyl, in particular methyl, it also being possible for R
1
and R
2
together to be tetramethylene or pentamethylene which is unsubstituted or substituted by one or more lower alkyl groups, and R
4
is hydrogen.
Specific examples are 3-methylbutyn-3-ol, 3,7-dimethyl-l-octyn-3-ol(hydrodehydrolinalool), 3,7-dimethylocta-6-en-1-yn-3-ol(dehydrolinalool), 3,7,11-trimethyldodeca-6,10-dien-1-yn-3-ol(dehydronerolidol), 3,7,11-trimethyldodeca-6-en-1-yn-3-ol and 3,7,11-trimethyldodec-1-yn-3-ol.
A particularly suitable isopropenyl ether of the formula III is isopropenyl methyl ether.
The preparation of the isopropenyl ethers of the formula III
where R
6
has the abovementioned meanings, as described more comprehensively and claimed in German Patent
Application 19 726 667.3, is carried out according to stage (b) by reacting a ketal of the formula IV
with propyne and/or allene in the gas phase in the presence of a heterogeneous catalyst containing zinc or cadmium and silicon and oxygen.
Although the mechanism of this reaction is not known in detail, the reaction may be regarded formally as if one mole of an alcohol
Breuer Klaus
Demuth Dirk
Etzrodt Heinz
Hibst Hartmut
Kaeshammer Stefan
BASF - Aktiengesellschaft
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Padmanabhan Sreeni
LandOfFree
Preparation of unsaturated ketones does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Preparation of unsaturated ketones, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Preparation of unsaturated ketones will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2586766