AN IMPROVED PROCESS FOR THE PREPARATION OF SUBSTITUTED ISOFLAVONE DERIVATIVES

摘要

The invention relates to a process for the preparation of pure isoflavone derivatives of general formula (I), wherein R stands for hydrogen or isopropyl, R<2> and R<3> stand for hydrogen or C1-2 alkoxy by reacting a rezorcinol-derivative of general formula (III) wherein R<2> and R<3> are as given above with ethyl-orthoformiate of the formula (IV): (C2H5O)3CH in the presence of a base and optionally by alkylating the product. The process is carried out by subjecting the compounds of general formula (III) and (IV), wherein R<2> and R<3> are as given above, to ring-closure at 70-100 DEG 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 R<2> and R<3> are as given above, and whereby the product of general formula (VII), wherein R<2> and R<3> are as given above, continuously precipitates from the mixture and filtering the product of general formula (VII) after cooling from the reaction mixture and/or adding a polar or apolar solvent to the reaction mixture and selectively dissolving thus the side product and filtering the product of general formula (VII), wherein R<2> and R<3> are as given above, and/or adding to the reaction mixture an almost equivalent amount of anhydrous potassium carbonate and isolating the crystallized double salt of general formula (V) wherein R<2> and R<3> 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).