Preparation of fluorinated 1,3-benzodiozanes

Compound of the general formula (I-a) or (I-b),

• where
• R1, R2, R3, R4 are each independently H, CN, NO2, NH2, OH, halogen, linear or branched, optionally partly fluorinated or perfluorinated C1-C4-alkyl radicals, linear or branched, optionally partly fluorinated or perfluorinated C1-C4-alkoxy radicals, CHO, COOH, COOR, SO2CH3, SO2Hal, optionally substituted phenyl or pyridyl radicals, fluorocarbonyl, benzoyl, trifluoroacetyl, phenoxy, isocyanato, SO2F and difluorochloromethyl radicals, where R is a C1-C4-alkyl radical and Hal is a halogen radical,
• x is H, Cl or F.