Polyhalogen-substituted cinnamic acids and cinnamic acid derivatives and a process for the preparation of polyhalogen-substituted cinnamic acids and cinnamic acid derivatives

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 8 )(R 7 ), where R 5 represents hydrogen or C 1 -C 10 -alkyl, phenyl or benzyl and R 6 and R 7 are identical or different and in each case represent 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) a diazonium salt of the formula (IV)

wherein

R 1 , R 2 , R 3 and R 4 have the meaning indicated in formula (III) and

A ⊖ represents an equivalent of halide, hydrogensulfate, nitrate, acetate or tetrafluoroborate ions or ½ an equivalent of sulfate ions or ⅓ an equivalent of phosphate ions,

with (2) a compound of the 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,

R 8 represents hydrogen or methyl and

A ⊖ represents an equivalent of chloride, hydrogensulfate or acetate or ½ an equivalent of sulfate.

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, and tris-(dibenzylidene-acetone)Pd 2 and 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 the diazonium salt of the formula (IV) is prepared from a corresponding aniline by reaction with sodium nitrite in acidic, aqueous solution or by reaction with an alkyl nitrite in acidic methanol and the salt is employed in the form of a reaction mixture obtained during its preparation.

5. The process according to claim 1 , wherein from about 0.5 to about 2 moles of the compound of the formula (V) are employed, per mole of diazonium salt of the formula (IV).

6. The process according to claim 1 , wherein the process is carried out without a base.

7. 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 where R 5 hydrogen; and

R 8 represents hydrogen, chlorine, bromine or optionally substituted C 1 -C 10 -alkyl,

the process comprising: reacting (1) a diazonium salt of the formula (IV)

wherein

R 1 , R 2 , R 3 and R 4 have the meaning indicated in formula (III) and

A ⊖ represents an equivalent of halide, hydrogensulfate, nitrate, acetate or tetrafluoroborate ions or ½ an equivalent of sulfate ions or ⅓ an equivalent of phosphate ions,

with (2) a compound of the 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.