A composition, which comprises a) an organic material susceptible to oxidative, thermal or light-induced degradation; and b) a compound of formula I (Formula I) (I) wherein R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 are independently from each other H, C1-C8-alkyl, C4-C8-cycloalkyl, phenyl, C1-C4-alkoxy or halogen; n is 1, 2, 3, or 4; and when n is 1 A is —C(=0)-OR′1, —C(=0)-N(R′2)(R′3), —CN, phenyl, which is unsubstituted or substituted by one or more C1-C8-alkyl, C4-C8-alkoxy, C5-C7-cycloalkyl or halogen, —H or —S02-phenyl; when n is 2 A is —C(=0)-O—Z1—O—C(=0)-, —C(=0)-N(R″1)—Z2—N(R″2)—C(=0)- or piperazine-N,N′-biscarbonyl.