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.