R6 and R7 independently of one another each very particularly preferably represent hydrogen, very particularly preferably represent respectively optionally fluorine- or chlorine-substituted C1-C4-alkyl, C3-C6-cycloalkyl, C1-C4-alkoxy, C3-C4-alkenyl or C1-C4-alkoxy-C2-C4-alkyl, very particularly preferably represent respectively optionally fluorine-, chlorine-, bromine-, methyl-, methoxy- or triflu