Patent ID: 7307192

Claim:
A process for the preparation of a crystalline isomeric mixture of compounds of formulae I and II which process comprises the following steps: a) the slow addition of aluminium chloride, in portions in the course of from 2 to 3 hours, so that a local overdosing of aluminium chloride is avoided, to a solution comprising 1,1,3-trimethyl-3-phenylindan having a low oligomer content and isobutyric acid halide in 2-dichlorobenzene at a reaction temperature of from 0° C. to 5° C., an isomeric mixture consisting of compounds of formulae Ia and IIa being obtained b) enol chlorination of compounds Ia and IIa, an isomeric mixture consisting of compounds of formulae Ib and IIb being obtained c) hydrolysis of the chlorinated isomeric mixture from step b).