PROCESS FOR THE PREPARATION OF SUBSTITUTED ISOFLAVONE DERIVATIVES

The invention relates to a process for the preparation of pure isoflavone derivatives of general formula (1), wherein R stands for hydrogen or isopropyl, R2 and R3 stand for hydrogen or C1-2 alkoxy by reacting a rezorcinol-derivative of general formula (III) wherein R2 and R3 are as given above with ethyl-orthoformiate of the formula (IV): (C2H5O)3CH in the presence of a bass and optionally by alkylating the product. The process is carried out by subjecting the compounds of general formula (III) and (IV), wherein R2 and R3 are as given above, to ring-closure at 70-100 .degree.C in the presence of an organic solvent, preferably dimethyl-formamide and/or isopropanol in a 0.3-2-fold volume calculated to the volume of the rezorcinol derivatives and/or in the presence of excess of the ester of formula (IV) in order to produce a 20-70 % by weight solution (supersaturated) of the product of general formula (VII) wherein R2 and R3 are as given above, an d whereby the product of general formula (VII), wherein R2 and R3 are as given above, continuously precipitates f rom the mixture and filtering the product of general formula (VII) after cooling from the reaction mixture and/or adding a po lar or apolar solvent to the reaction mixture and selectively dissolving thus the side product and filtering the product of ge neral formula (VII), wherein R2 and R3 are as given above, and/or adding to the reaction mixture an almost equivalent a mount of anhydrous potassium carbonate and isolating the crystallized double salt of general formula (V) wherein R2 and R3 are as given above, whereafter the products of general formula (V) or (VII) are reacted with isopropil-halide and optionally separating the pure product containing at most 0.5 % by weight of contaminating compound of general formula (VI).