Pyrene-benzoylthiophene exciplexes as selective catalysts for the [2+2] cycloaddition between cyclohexadiene and styrenes.

Efficient intramolecular fluorescence quenching in pyrene-benzoylthiophene systems leads to formation of exciplexes. These species interact with 1,3-cyclohexadiene (or styrenes), leading to reactive excited triplexes. The overall process affords [2+2] cross-cycloadducts with an average yield of 57%.