Compounds of the general formula I ##STR1## are described in which R.sup.1 is a group of the formula ##STR2## and R.sup.2 is a hydrogen atom or a methyl group, orR.sup.1 and R.sup.2 jointly form an optionally substituted 5- or 6-membered ring,R.sup.3 is a hydrogen atom, a methyl group or an optionally substituted phenyl group,R.sup.4 is a hydrogen or halogen atom, a methyl group, an optionally substituted benzoyl group or a group of the formula ##STR3## n is zero or 1, X is a hydrogen or chlorine atom, an alkyl group containing 1 to 4 carbon atoms or one of the groups OA, CH.sub.2 OA, CH.sub.2 NHA or C.sub.2 H.sub.4 OA, andA is an acryloyl or methacryloyl group,the compounds containing in each case at least one group A. The compounds are suitable for the production of photoresists and printing plates as diffusion-resistant photoinitiators in photopolymerizable mixtures.