Process for the manufacture of cinnamic acid derivatives

PCT No. PCT/EP93/02317 Sec. 371 Date Apr. 28, 1994 Sec. 102(e) Date Apr. 28, 1994 PCT Filed Aug. 27, 1993 PCT Pub. No. WO94/05621 PCT Pub. Date Mar. 17, 1994.A novel process for the manufacture of a cinnamic acid derivative of the formula I wherein R1 signifies hydrogen or C1-8-alkyl and R2 signifies hydrogen, C1-10-alkyl, C1-10-hydroxyalkyl or C1-4-alkoxy-C1-10-alkyl, is described in which a 4-R1O-halobenzene is reacted with acrylic add or an acrylic acid ester CH2=CHCOOR2 using a heterogeneous palladium catalyst in the presence of the alkanoic acid ammonium salt formed from a C2-5-alkanoic acid and an aliphatic mono-, di- or trialkylamine or heterocyclic amine. In the case of the manufacture of the cinnamic acid derivative I in which R2 signifies hydrogen, the reaction can be carried out in the presence of the amine in place of the alkanoic acid ammonium salt. A further aspect of the described invention comprises reacting the 4-R1O-iodobenzene with the product of the Michael addition of an acrylic acid ester CH2=CHCOOR2', wherein R2' has the above significance of R2 except hydrogen, with an aliphatic or heterocyclic primary of secondary amine using a heterogeneous palladium catalyst and in the presence of a C2-5-alkanoic add in order to manufacture the above cinnamic add derivatives with the exception of the substituted cinnamic acid itself. In view of their UV-B absorbing properties the thus-manufactured cinnamic acid derivatives are suitable as UV-B filters for cosmetic agents, e.g. sunscreen agents.