| abstract |
The invention relates to a process for the preparation of flavan derivatives of general formula I wherein R 1 represents a lower alkyl, halogen, cyano, hydrogen, R 2 represents a halogen or hydrogen atom, R 3 represents hydrogen, a lower alkyl radical, methoxy, halogen, trifluoromethyl, alkylamino, amine, cyano, R 4 represents hydrogen, lower alkylamino, lower alkyl, provided that when R 3 and R 4 represent both hydrogen atoms, one of the substituents of R 1 or R 2 represents hydrogen or lower alkyl and provided that at least one of the substituents of R 1, R 2, R 3, R 4 represents hydrogen, characterized by the reaction of a compound of general formula II: wherein R 1 and R 2 have the meanings given above above, X represents a hydroxy group or a halogen atom, with a compound of the general formula III wherein R 3 and R 4 are as defined above, at a temperature in the range 150 ... 205 degree C. |