Compounds of the formula (I) wherein Q is a direct bond or an n-valent linking group; n is an integer 2, 3, or 4; Z is for example C1-C20alkylene, C2-C20alkenylene, C5-C8cycloalkylene or C5-C8cycloalkenylene; Y is for example C6-C20aryl or C3-C20heteroaryl; R1 is for example hydrogen, C2-C5alkenyl, C3-C8cycloalkyl, C1-C12alkyl, phenyl, naphthyl, C3-C20heteroaryl, C1-C8alkoxy, benzyloxy or phenoxy; R2 is for example C1-C20alkyl, C2-C12alkenyl, C4-C8cycloalkenyl, C2-C12alkinyl, C3-C10cycloalkyl, phenyl or naphthyl; R15, R16, R17, R18, R19 and R20 independently of each other for example are hydrogen, halogen, C1-C20alkyl, C6-C20aryl or C4-C20heteroaryl; provided that a compound wherein R15, R16, R17, R18, R19 and R20 are hydrogen, Y is thienyl, R1 is methyl, R2 is ethyl, n is 2, Q is a direct bond and Z is n-propylene and a compound wherein R15, R16, R17, R18, R19 and R20 are hydrogen, Y is thienyl, R1 is methyl, R2 is ethyl, n is 2, Q as an n-valent linking group is methylene and Z is methylene are excluded; are reactive photoinitiators in particular in electronic applications.