Polyhalogen-substituted cinnamic acids and cinnamic acid derivatives and a process for the preparation of polyhalogen-substituted cinnamic acids and cinnamic acid derivatives
View Patent ↗Polyhalogenated cinnamic acids and cinnamic acid derivatives are prepared by reacting diazonium salts accessible from polyhalogenated anilines with acrylic acid or acrylic acid derivatives in the presence of a homogeneous, palladium-containing catalyst at about −5 to about +100° C. Some of the cinnamic acids and cinnamic acid derivatives obtainable in this way are new. Cinnamic acids and cinnamic acid derivatives which can be prepared according to the invention can be used for the preparation of indanones which are precursors for agro- and pharmaceutical chemicals and for substances having liquid-crystalline properties.
1. A process for preparing a compound of formula (III)
wherein R 1 , R 2 , R 3 and R 4 are identical or different and in each case represent hydrogen, fluorine, chlorine or bromine, at least two of these radicals being other than hydrogen and
X represents OR 5 or N(R 6 )(R 7 ), where R 5 represents hydrogen or optionally substituted C 1 -C 10 -alkyl, optionally substituted phenyl or benzyl and R 6 and R 7 are identical or different and in each case represent optionally substituted C 1 -C 10 -alkyl and
R 8 represents hydrogen, chlorine, bromine, or optionally substituted C 1 -C 10 -alkyl,
the process comprising: reacting (1) an aniline of the formula (VI)
wherein
R 1 , R 2 , R 3 and R 4 have the meaning indicated in formula (III) with sodium nitrite in aqueous sulfuric acid or sulfuric acid in combination with methanol, or with an alkyl nitrite selected from the group consisting of methyl, ethyl, butyl and amyl nitrite into a diazonium salt and reacting (2) the resulting reaction mixture
with a compound of formula (V)
wherein
X has the meaning indicated in formula (III) and
R 8 represents hydrogen, chlorine, bromine or optionally substituted C 1 -C 10 -alkyl,
in the presence of a homogeneous, palladium-containing catalyst at a temperature ranging from about −5 to about +100° C.
2. The process according to claim 1 , wherein
R 1 represents hydrogen or chlorine,
R 2 represents hydrogen, fluorine, chlorine or bromine,
R 3 represents hydrogen or chlorine and
R 4 represents fluorine or chlorine, at least one of the radicals R 1 , R 2 and R 3 being other than hydrogen,
R 5 represents hydrogen, methyl, ethyl, isopropyl or benzyl,
R 6 and R 7 represent methyl or ethyl, and
R 8 represents hydrogen or methyl.
3. The process according to claim 1 , wherein, the palladium-containing catalyst is selected from the group consisting of PdCl 2 , PdBr 2 , Pd(NO 3 ) 2 , H 2 PdCl 4 , Pd(CH 3 COO) 2 , Na 2 PdCl 4 , K 2 PdCl 4 , Pd(II) acetylacetonate, tetra-(trisphenylphosphine)Pd, tris-(dibenzylidene-acetone)Pd 2 and wherein the palladium-containing catalyst is used in an amount ranging from about 0.001 to about 10 mol %, based on the diazonium salt of the formula (IV).
4. The process according to claim 1 , wherein from about 0.5 to about 2 moles of compounds of formula (V) are employed, per mole of diazonium salt of the formula (IV).
5. The process according to claim 1 , wherein the process is carried out without a base.
6. The process according to claim 1 , wherein,
R 1 , R 2 , R 3 , R 4 , R 8 has the meaning indicated in formula (III) and
X represents OR 5 , where R 5 represents hydrogen.