Compounds of formula II and X ##STR1## wherein X is O, S, SO.sub.2, methylene, isopropylidene or NCOR.sub.7 where R.sub.7 is alkyl or phenyl, Y is a direct bond or methylene, n is 1 or 2, R.sub.4 is alkyl, phenyl, naphthyl, cycloalkyl, aralkyl, camphoryl, CF.sub.3, CCl.sub.3, F or NH.sub.2 ; or is alkylene, phenylene or naphthylene, R.sub.5 is hydrogen or halogen, R.sub.6 is hydrogen, alkyl, phenyl or cyano, R.sub.8 is substituted phenyl, substituted naphthyl, anthryl or phenanthryl, R.sub.9 is alkyl R.sub.10 is alkyl or substituted phenyl, and R.sub.11 is alkyl, substituted phenyl, naphthyl, camphoryl, alkylene, phenylene or naphthylene, are latent curing catalysts for acid-curable stoving lacquers. They are distinguished by satisfactory solubility in the acid-curable resin systems, can be stored virtually indefinitely in the dark and, when exposed to shortwave light, make it possible to cure the resins by acid catalysts at a relatively low temperature.