There are provided compounds comprising optionally substituted (FORMULA I) fused with one or two optionally substituted (FORMULA II), wherein A and E each independently represent —CH2—, —NH—, -0-, —S—, or —C(═O)— and B represents a bond, —CH2—, —NH—, -0-, —S—, or —C(═O)—, said compound having directly or indirectly attached thereto at least one acyl and/or oxime ester group. Such compounds are useful inter alias as photoinitiators.