Process for the preparation of indenonecarboxylic acids

Claim 1

A process for the preparation of an indenonecarboxylic acid of the formula I ##STR42## in which R 3 is Cl or Br, and R, R 1 and R 2 are identical or different and R is a n-alkyl radical having 1 to 4 C atoms, or is H, Cl, Br or F, R 1 is a n-alkyl radical having 1 to 4 C atoms, or is H, and R 2 is H or CH 3 , or R 1 and R 2 together are the group --CH 2 CH 2 CH 2 --, in which latter case the bond to the six-membered ring is via the C atoms in the 5-position and 6-position of the nucleus, which comprises subjecting an aromatic compound of the formula II ##STR43## in which the H atoms on at least 2 adjacent C atoms of the nucleus have not been replaced by substituents and in which R, R 1 and R 2 are as defined for formula I, either together with a diahalogenomaleic anhydride of the formula III ##STR44## or together with an ester of the formula IV ##STR45## in which formulae R 3 is as defined for formula I and R 4 is in each case a low-molecular aliphatic radical, a cycloaliphatic radical, an aliphatic-aromatic radical or an aromatic radical, in each case in an approximately stoichiometric ratio, to a condensation reaction in the presence of AlCl 3 and if desired in the presence of inert fluxes and/or solvents, at temperatures between 40° and 150° C., and hydrolysing the reaction product thus obtained.