Abstract: The compounds of the formula I ##STR1## in which R.sub.1 to R.sub.5 denote hydrogen; alkyl, alkoxy, alkylmercapto, alkylsulfinyl, alkylsulfonyl, alkylsulfonyloxy each of which can be halogenated, halogen or nitro, R.sub.6 to R.sub.10 denote hydrogen; alkyl, alkoxy, alkenyloxy, alkylmercapto, alkenylmercapto, alkylsulfonyl or C.sub.3 -hydroxyalkyl each of which can be halogenated, (substituted) benzyloxy, alkoxycarbonyl or NRR', and R.sub.7 and R.sub.8 together can form a (substituted) alkylenedioxy radical,X denotes OR.sub.11 in which R.sub.11 denotes optionally halogenated alkyl, cycloalkyl, alkenyl or alkynyl or optionally halogenated benzyl, or SR.sub.12 in which R.sub.12 denotes alkyl or benzyl each of which can be halogenated, andY denotes oxygen or sulfur, subject to the proviso that, if R.sub.1 and R.sub.5 both denote fluorine and R.sub.2, R.sub.3 and R.sub.4 denote hydrogen, the radicals R.sub.6 to R.sub.10 must not each represent halogenated (C.sub.1 -C.sub.