A simple approach to indeno-coumarins via visible-light-induced cyclization of aryl alkynoates with diethyl bromomalonate

Visible-light-induced triple-domino cyclization between aryl alkynoates and diethyl bromomalonate is developed for the synthesis of indeno-coumarins. This one-pot method substantially simplified the production process of indeno-coumarins. A series of indeno-coumarins could be isolated in moderate to high yields. It was found that the obtained indeno-coumarins could be used as an additional photosensitizer to initiate this transformation. The possible radical mechanism accompanying the process of electron transfer and energy transfer is proposed with respect to the results of ESI-MS analysis, cyclic voltammetry, Stern-Volmer quenching experiments and control experiments. The photoluminescence properties (emission spectras and quantum yields) of the obtained indeno-coumarins 6 were investigated.