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Photoelimination of Nitrogen from Polycyclic Diazirines: Spectroscopic Study and Supramolecular Control of Photoreactivity

Photochemical elimination of nitrogen from diazirine derivatives and formation of carbene intermediates has been intensively investigated by physical-organic chemical community because of the fundamental interest in carbene reactivity [1]. Platz et al. reported spectroscopic studies on adamantane diazirine derivative 1 [2], whereas Bonneau, Wirz et al. indirectly proved the presence of carbenes by trapping them with pyridine, resulting in the corresponding ylides [3]. However, a direct spectroscopic detection of the corresponding adamantane carbene by laser flash photolysis (LFP) still has not been reported. As part of our interest in the chemistry of carbenes and synthesis of strained molecules [4], we have prepared diazirines 1-3 and studied their photochemical reactivity in different solvents and inclusion complexes. We found that supramolecular hosts affect the photochemical reaction selectivity in a way that may be correlated with the excited state manifold of the photochemical reaction, contrary to previous reports of Ramamurthy et al. [5] Moreover, reactivity of 1-3 has been investigated by LFP, allowing for a direct detection of singlet adamantyl and pentacycloundecanyl (PCU) carbenes in pentane solution at -100 °C.

diazirines ; carbenes ; transient spectroscopy ; supramolecular chemistry

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