R¹ and R² may be the same or different and are a C₁-C₂₅alkyl group, which can be substituted by fluorine, chlorine or bromine, an allyl group, which can be substituted one to three times with C₁-C₄alkyl, C₅-C₁₂-cycloalkyl which can be substituted one to three times with C₁-C₈alkyl and/or C₁-C₈alkoxy, C₅-C₁₂cycloalkyl condensed one or two times by phenyl which can be substituted one to three times with C₁-C₄-alkyl, halogen, nitro or cyano, an alkenyl group, a cycloalkenyl group, an alkynyl group, a haloalkyl group, a haloalkenyl group, a haloalkynyl group, an aldehyde group, an ester group, a carbamoyl group, a ketone group, a silyl group, a siloxanyl group, A³ or —CR³R⁴—(CH₂)_m-A³ wherein

R³ and R⁴ independently from each other stand for hydrogen or C₁-C₄alkyl, or phenyl which can be substituted one to three times with C₁-C₄alkyl,

A³ stands for aryl or heteroaryl, which can be substituted one to three times with C₁-C₈alkyl and/or C₁-C₈alkoxy, and m stands for 0, 1, 2, 3 or 4,

A¹ and A² are independently of each other a group

R⁵ is a group NR⁸R⁹,

wherein R⁸ is a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, a heterocyclic group, an aralkyl group,

R⁹ is an aryl group or a heteroaryl group,

or R⁸ and R⁹ together with the nitrogen atom to which they are bonded form a five or six membered heterocyclic ring condensed by one or two optionally substituted phenyl groups,

wherein

R⁶ and R⁷ may be the same or different and are a hydrogen atom, a C₁-C₂₅alkyl group, a cycloalkyl group, an aralkyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a mercapto group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, an aryl group, a heterocyclic group, a halogen atom, a haloalkyl group, a haloalkenyl group, a haloalkynyl group, a cyano group, an aldehyde group, a carboxyl group, an ester group, a carbamoyl group, a nitro group, a silyl group, a siloxanyl group, a substituted or unsubstituted vinyl group, a group NR⁸R⁹, wherein R⁸ and R⁹ independently of each other stand for a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, a heterocyclic group, an aralkyl group, or R⁸ and R⁹ together with the nitrogen atom to which they are bonded form a five or six membered heterocyclic ring, which can be condensed by one or two optionally substituted phenyl groups.