US 4,585,594 AGrant
Preparation of 4-Substituted but-3-Ene-1-Carboxylic Acids and Their Esters
Issue Date:1986-04-29
•6 Claims
Abstract
4-Substituted but-3-ene-1-carboxylic acids and their esters R.sup.1 R.sup.2 C.dbd.CH--CH.sub.2 --CO--O--R.sup.3 (I, where R.sup.1 is an organic radical, R.sup.2 is H or R.sup.1, or R.sup.1 and R.sup.2 together form a 5-membered to 20-membered ring, and R.sup.3 is H or lower alkyl) are prepared by carbonylation of R.sup.1 R.sup.2 C(OH)--CH.dbd.CH.sub.2 (II) in the presence of an alcohol R.sup.3' --OH (III, where R.sup.3' is lower alkyl) or, for the preparation of the acids I alone, in the absence of an alcohol III, at from 50.degree. to 150.degree. C. and under from 200 to 700 bar, using a complex of a palladium halide and a tertiary organic phosphine.
Metadata
Assignee
- BASF Aktiengesellschaft
Inventors
- Walter Himmele
- Werner Hoffmann
- Lothar Janitschke
Application Information
Application Number:US 6805140
Filing Date:1984-12-11
Priority Date:1984-12-11
Art Unit:126
Classifications
IPC:
C07C 5114C07C 6736
Field of Search:
560562260549207;214;8;55;101;104406;465;491;495;517410.9 M;410.9 N;413 R323;427
Patent Drawings
This patent does not have any drawings.
Description
The present invention relates to a novel process for the preparation of 4-substituted but-3-ene-1-carboxylic acids or their esters of the general formula I ##STR1## where R.sup.1 is an organic radical, R.sup.2 is hydrogen or an organic radical, and R.sup.1 and R.sup.2 may furthermore be bonded to one another to form a 5-membered to 20-membered ring and should be inert under the reaction conditions described below, and R.sup.3 is hydrogen or lower alkyl.
Tsuji et al., in J. Am. Chem. Soc. 86 (1964), 4350-4353, disclose that ethyl pent-3-ene-1-carboxylate (I, where R.sup.1 is Me, R.sup.2 is H and R.sup.3 is Et) can be prepared by carbonylation of but-1-en-3-ol with carbon monoxide and ethanol in the presence of palladium chloride as a carbonylation catalyst. However, the yield of only 39% achieved in this procedure is unsatisfactory for industrial purposes.
Furthermore, Bittler et al., in Angew. Chemie, 80 (1968), 352-359, disclose that allyl alcohol and methanol can be carbonylated using a palladium chloride/triphenylphosphine complex to give methyl but-3-enecarboxylate in 65% yield. According to the authors (cf. loc cit, page 355), the carbonylation of the allyl alcohol takes place with retention of the double bond, so that the 4-substituted but-3-enecarboxylates have to be prepared using, as starting materials, the allyl alcohols ##STR2## which are difficult to obtain.
It is an object of the present invention to make the compounds I more readily accessible, these compounds generally being important for organic syntheses, and some of them being directly useful as fragrance materials.
We have found, unexpectedly in view of the work by Bittler et al., that this object is achieved by a process for the preparation of the compounds (I) defined at the outset, by carbonylation of a derivative of allyl alcohol with the aid of a palladium halide, wherein an allyl alcohol II ##STR3## is carbonylated with carbon monoxide at 50.degree.-150.degree. C. and under 200-700 bar,
(a) together with an alcohol III
where R.sup.3' is lower alkyl, if a predominant amount of an ester I is to be prepared, or
(b) without a further reactant where an acid I is to be prepared, in the presence of an effective amount of a complex of a palladium halide and a tertiary phosphine (IV).
The starting compounds II are obtainable in a simple manner from the corresponding carbonyl compounds R.sup.1 --CO--R.sup.2 and vinyl magnesium halides. II can also be prepared from the carbonyl compounds and acetylides, such as sodium acetylide, with subsequent partial hydrogenation of the ethynyl group to the vinyl group.
On the basis of the very extensive investigations carried out to date, the nature of the compounds II, ie. the type of organic radicals R.sup.1 and R.sup.2, is in principle unimportant with regard to the novel process, provided that these radicals do not contain any substituents or groups which are reactive under the carbonylation conditions. Examples of such reactive radicals are alkenyl groups having terminal double bonds; if, on the other hand, the double bond is an internal one, it is as a rule virtually never attacked under the reaction conditions.
Examples of suitable radicals R.sup.1 and R.sup.2 are aliphatic radicals of 1 to 30 carbon atoms, cycloaliphatic radicals having 3 to 12 ring members, aromatic radicals possessing from 1 to 3 isocyclic or heterocyclic aromatic rings, mixed radicals containing aliphatic and/or cycloaliphatic and/or aromatic groups in any sequence, and cyclic radicals which have from 3 to 20 ring members, are formed by R.sup.1 and R.sup.2 together and can in turn be substituted by the above radicals.
All of these radicals can furthermore contain substituents such as halogen, eg. fluorine or chlorine, hydroxyl (which in general is virtually never attacked during the carbonylation according to the invention), substituted amino, cyano, nitro, alkoxy, acyl, acyloxy, carbalkoxy, thiol, mercaptan, carboxamide or alkylsulfonyl. Particularly important alcohols II are those whose molecule contains one or more isoprene skeletons; the compounds I derived from these are often typical fragrance materials.
Suitable alcohols III are mainly lower alcohols, such as methanol and ethanol, since the carbonylation proceeds most rapidly with these. Higher alcohols of not more than about 6 carbon atoms can in principle also be used, although it is frequently more advantageous to introduce these into the molecule by transesterification of the methyl or ethyl esters I.
In general, it is preferable to use a molar excess of the alcohol III over the alcohol II. Usually, the molar ratio of III to II is from 2:1 to 6:1. If III is used as a solvent, this ratio may also be higher.
If the procedure is carried out in the absence of a further reactant, ie. without an alcohol III, the acids I are obtained. Predominant amounts of acid are also generally obtained when a tertiary alcohol III, eg. tert.-butanol, is used.
The carbonylation catalysts are complexes of a palladium halide, eg. the bromide or in particular the chloride, and a tertiary organic phosphine (IV). Since formation of these complexes takes place directly under the reaction conditions, the said complexes are advantageously employed in the form of their components; however, it is of course also possible to start from the preprepared complexes, eg. Pd(PPh.sub.3).sub.2 Cl.sub.2 (Ph=phenyl).
The tertiary phosphines IV are of the general formula IV ##STR4## where R.sup.4, R.sup.5 and R.sup.6 are each an organic radical.
In particular, R.sup.4, R.sup.5 and R.sup.6 can each be alkyl of 4 to 18 carbon atoms, C.sub.1 -C.sub.4 -alkylphenyl or, especially, phenyl. Two of these radicals may furthermore be bonded to one another to form a 5-membered to 8-membered ring, and it is of course also possible to use compounds possessing 2 or more tertiary phosphine groups, eg. 1,2-bis-(diphenylphosphino)-ethane.
The type of phosphines is in principle unimportant, so that it is in general preferable to use the cheapest member of this class of substances, ie. triphenylphosphine.
It is also advantageous to carry out the reaction in the presence of free phosphine, ie. phosphine which is not bonded in a complex. The preferred molar ratio of phosphine to Pd is from 3:1 to 10:1.
It is not possible to state a particular value for the effective amount of the catalyst because the reaction takes place in principle with infinitely small amounts of Pd, but is of course then very slow, and because large amounts have no adverse effect. Hence, the amount of Pd depends on the reactivity of the alcohol II and on the reaction time desired. In general, the amount of Pd is from 0.1 to 5 g per mole of II.
According to the general principles of process engineering, the reaction takes place most readily and most rapidly in the substantially homogeneous liquid phase. In general, homogeneity results automatically under the reaction conditions owing to the presence of the alcohol III, so that an additional solvent need not be used. If, however, the alcohol II is sparingly soluble, it is advisable to use a solvent, such as toluene, diethyl ether or tetrahydrofuran.
The pressure, which for the most part corresponds to the CO partial pressure, is in general from 100 to 650, in particular from 300 to 600, bar, and the recommended temperature is from 50.degree. to 150.degree. C., preferably from 90.degree. to 110.degree. C. Under these conditions, and using the recommended amounts of catalyst, the reaction times are about 1-24 hours.
The novel process can be carried out continuously or batchwise, and the method used is identical to the conventional carbonylation technique, so that more detailed description of this can be dispensed with. The same applies to the working up of the reaction mixtures. Owing to the sensitivity of the phosphines to oxidation, it is advisable to carry out the procedure in the absence of atmospheric oxygen.
When the alcohol III is also used, the products obtained are mainly the esters I, the free acids 1 also resulting; tertiary alcohols III generally give larger amounts of the acid. The amount of by-products is low in every case, although it was expected that the alcohols II would be dehydrated under the reaction conditions. The compounds I can be formed in the cis or trans form, predominant amounts of the trans isomer usually being obtained.
Examples
Various alcohols II were reacted with various alcohols III, in each case in the absence of atmospheric oxygen, at 100.degree. C., in the presence of palladium chloride and triphenylphosphine (Pph.sub.3), to give the acids or esters I.
Details of the other reaction conditions and of the results of the experiments are shown in the Table below. About 98% of the stated pressure is due to the CO partial pressure. Each of the reactions was terminated when scarcely any further CO was consumed.
The products were identified by means of gas chromatographic, H--NMR, .sup.13 C--NMR, mass spectroscopic and IR analysis. The yields were determined gravimetrically; where separation into the acid and the ester presented difficulties, only the sum of the yields was determined. Boiling points and melting points are stated wherever they were obtained directly from the experiments.
Claims
We claim:
1. A process for the preparation of a 4-substituted but-3-ene-1-carboxylic acid or its esters of the formula I ##STR5## where R.sup.1 is an organic radical, R.sup.2 is hydrogen or an organic radical, and R.sup.1 and R.sup.2 may furthermore be bonded to one another to form a 5-membered to 20-membered ring and should be inert under the reaction conditions described below, and R.sup.3 is hydrogen or lower alkyl, by carbonylation of a derivative of allyl alcohol with the aid of a palladium halide, wherein an allyl alcohol II ##STR6## is carbonylated with carbon monoxide at 50.degree.-150.degree. C. and under 200-700 bar, (a) together with an alcohol III where R.sup.3' is lower alkyl, if a predominant amount of an ester I is to be prepared, or (b) without a further reactant where an acid I is to be prepared, in the presence of an effective amount of complex of a palladium halide and a tertiary phosphine (IV).
2. A process as claimed in claim 1, wherein the carbonylation with carbon monoxide is carried out at a temperature of 90.degree. to 110.degree. C. and under a pressure of 300 to 600 bar.
3. A process as claimed in claim 1, wherein the molar ratio of phosphine to palladium is from 3:1 to 10:1.
4. A process as claimed in claim 1, wherein the amount of palladium is from 0.1 to 5 g per mole of the allyl alcohol II.
5. A process as claimed in claim 4, wherein the molar ratio of phosphine to palladium is from 3:1 to 10:1.
6. A process as claimed in claim 1, wherein the molar ratio of the alcohol III to the allyl alcohol II is from 2:1 to 6:1.
Non-Patent Literature (2)
- Tsuji et al., in J. Am. Chem. Soc. 86 (1964), pp. 4350-4353.
- Bittler et al., Angew. Chemie, 80 (1968), pp. 352-359.