engleski

From polycyclic diazirines to carbenes: supramolecular control of photoreactivity

Photochemical elimination of nitrogen from diazirines leading to carbene intermediates is a valuable tool for investigating carbene reactivity.[1] Platz et al. reported spectroscopic studies on adamantane diazirine 2, [2] whereas Bonneau, Wirz et al. indirectly proved the formation of carbenes by trapping them with pyridine and obtaining the corresponding ylides.[3] However, photochemical reactivity of pentacycloundecane (PCU) diazirine 1 has not been explored in such detail. As part of our interest in the chemistry of carbenes and synthesis of strained molecules, [4] we prepared diazirines 1 and 2 and studied their photochemical reactivity in different solvents and in different supramolecular host molecules. We found that the presence of supramolecular hosts indeed affects the photochemical reaction pathways, e.g., complexation of diazirines with cyclodextrins ultimately changes the relative ratio of singlet and triplet carbene products. Furthermore, we found that product formation from singlet carbenes involves protonation and formation of carbocations, experimentally confirmed by the observed rearrangement of the PCU skeleton. We additionally corroborated our results by performing DFT computations on the starting diazirines as well as on the formed carbene intermediates.

Photochemical elimination ; polycyclic diazirines ; carbenes ; photoreactivity

nije evidentirano