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

Abstract

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 method for preparing an indanone derivative of the formula (VIIa): 
       
         
           
           
               
               
           
         
         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 
         R 8  represents hydrogen, chlorine, bromine or optionally substituted C 1 -C 10 -alkyl, 
         the method comprising: 
         (a) hydrogenating a polyhalogenated cinnamic acid or cinnamic acid derivative having the formula (III′) 
       
       
         
           
           
               
               
           
         
       
       wherein
 R 2′  represents chlorine and R 4′  represents fluorine or 
 R 2′  represents fluorine and R 4′  represents chlorine, and 
 (b) cyclizing the hydrogenated cinnamic acid or cinnamic acid derivative formed in step (a), thereby forming the indanone derivative of the formula (VIIa). 
 
     
     
         2 . The method according to  claim 1 , wherein the method is carried out without a base.