Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Patent
1996-08-22
1998-10-06
Killos, Paul J.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
560 47, 560 55, 560 64, 560 65, 560 76, 562452, 562465, 562495, C07C 6976, C07C 6364
Patent
active
058178627
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the preparation of cinnamic acid derivatives.
It is already known that olefins can be arylated by bromoaromatic compounds in the presence of palladium catalysts, phosphine ligands and a base (see R. F. Heck, Org. React. 27, 345-391 (1982)).
According to Y. Ben-David et al., Organometallics 11, 1995 (1992) the arylation of alkenes using chloro-aromatic compounds can only be carried out in the presence of bidentate phosphine ligands.
The reaction is frequently carried out with various amines (e.g. triethylamine, tributylamine, tetramethylethylenediamine), which may serve simultaneously as solvent. The bases employed may include alkali metal carboxylates in dimethylformamide (see EP-A 78 768) or alkali metal carbonates or hydrogen carbonates, given the simultaneous presence of a polar aprotic solvent (e.g. dimethylformamide, hexamethylphosphoric triamide, acetonitrile) and a phase transfer catalyst (see Tetrahedron Lett. 26, 2667-2670 (1985) and J. Org. Chem. 56, 1289-1293 (1991)).
Furthermore, the patent application WO 90/10617 discloses that, in a two-step process, p-methoxyaniline (=p-anisidine) can first of all be diazotized, and then the product can be converted using potassium iodide into 4-iodanisole. This product can subsequently be reacted with 2-ethylhexyl acrylate, in the presence of triethylamine and a palladium catalyst, to give 2-ethylhexyl 4-methoxycinnamate. This process involves a large number of steps and requires the recovery of alkali metal iodide.
The reaction of 4-iodoanisole with methyl acrylate and a stoichiometric quantity of tetramethyl-ethylenediamine in the presence of 1 mol% of palladium(II) acetate results, after 5 hours at 100.degree. C., in a yield of only 68% of methyl 4-methoxycinnamate (J. Org. Chem. 37, 2320-2322 (1972)).
The reaction of 4-bromoanisole with methyl acrylate and a stoichiometric quantity of tetramethyl-ethylenediamine in the presence of from 1 to 2 mol% of palladium(II) acetate and 2 to 4 mol% of triphenyl-phosphine gives, after 36 hours at 135.degree. C., a yield of methyl 4-methoxycinnamate of 54% (J. Am. Chem. Soc. 96, 1133-1136 (1974)).
DE 42 11 608 proposes the reaction of bromoaromatic compounds with acrylic acid derivatives in the presence of palladium catalysts and a large excess of phosphines, based on palladium. The phosphine produced in relatively large quantities in this reaction creates additional difficulties in isolating the product.
EP 0 509 426 describes the preparation of octyl p-methoxycinnamate from p-bromoanisole and octyl acrylate in the presence of a base and of a coupling catalyst in a polar aprotic solvent. All of the processes which have been disclosed to date produce bromide salts as by-products, resulting in a considerable pollution of the waste water or in a laborious recovery procedure. None of the processes known to date has a successful outcome with the corresponding chlorine derivative.
EP 103 544 describes a process for the arylation of acrylonitrile with p-chlorobenzaldehyde in the presence of chloro(4-formylphenyl)bis(triphenyl-phosphine)palladium(II), the product being obtained in a yield of only 18%.
There is therefore a need for a process which can be used to react the chloroaromatic compounds, which are less reactive but easier to prepare, in the presence of palladium catalysts with acrylic acid derivatives in high space-time yields and without the use of auxiliaries requiring any particular complexity.
A process has now been found for the preparation of cinnamic acid derivatives from chloroaromatic compounds and acrylic acid derivatives in the presence of palladium catalysts and a phosphine, which process is characterized in that a lipophilic, aliphatic phosphine is employed of the formula I ##STR1## in which R.sup.1 at each occurrence independently of one another is straight-chain or branched C.sub.1-6 -alkyl, C.sub.1-6 -alkoxy, C.sub.4-8 -cycloalkyl or C.sub.4-8 -cycloalkoxy, preferably branched C.sub.3-6 -alkyl, C.sub.3-6 -alkoxy or cyclohexyl, and C.sub.4-8 -cycloalkyl
REFERENCES:
Chemical Abstracts 116: 58980 CA 1991.
Christ Rainer
Heywang Ulrich
Meyer Volker
Poetsch Eike
Seubert Jurgen
Killos Paul J.
Merck Patent Gesellschaft mit beschrankter Haftung
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