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The photochemistry of 14 different substituted or-phenoxyacetophenones (1) was studied by CIDNPspectroscopy using an XeCl excimer laser (308 nm) and a 250 MHz 'H-NMR spectrometer. To characterize the excited states the electronic absorption and emission spectra as well as disappearance quantum yields were investigated also. -Two reaction channels were established: 1) P-cleavage from the singlet state;and 2) the formation of acetophenones via the respective enol forms where the origin of the polarization remains unclear. It is concluded that these are the main reaction channels, since all products formed show polarizations in the CIDNP-spectra. -In contrast to the current assumptions for the typical acetophenone reaction of (1) leading to the P-cleavage, we are led to interprete the CIDNP-spectra of (1) as a result of a reaction due to the phenoxy part with all characteristics of a photo-Claisen reaction.

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