Solvent and substituent effects on the photochemistry of norbornadiene-diarylacetylene Pauson-Khand adducts.

The photochemistry of Pauson-Khand cycloadducts of norbornadiene with a series of bis-aryl alkynes has been studied. Two types of photochemical transformation take place: photorearrangement to tricyclic ketones or photochemical 6π electrocyclization. High selectivity levels have been attained for each pathway, controlled by the polarity of the solvent, irradiation wavelength, and presence (or absence) of oxygen.