Patent ID: 8344136

Claim:
A process for the preparation of compounds of formula 1 wherein X is hydrogen, halogen, thiol, thioether, or amide of sulphonic acid or halide of sulphonic acid, R is hydrogen, alkyl, alkoxyalkyl, haloalkyl, aryl or arylalkyl, comprising the steps of a) reaction of the compound of formula 2 wherein X and R have the above mentioned meanings and Z is an halogen or a sulphonic ester, with an alcohol or a diol to give the ketal of formula 3 wherein X, R and Z have the above mentioned meaning and R 1 is an alkyl, linear or branched, or arylalkyl, and the two groups R 1 can be separated or joined to form a cycle, b) cyclization of the compound of formula 3 to form the compound of formula 4 wherein X, R and R 1 have the above mentioned meaning, c) hydrolysis of the compound of formula 4.