A facile visible-light-induced one-pot synthesis of 3-alkyl coumarins from simple salicylaldehydes

An efficient and mild one-pot stepwise method to synthesize 3-alkyl coumarins is reported. Various 3-alkyl coumarins were synthesized under 3 W blue LEDs irradiation at room temperature from cheap and easily available salicylaldehydes. Based on the results of control experiments and the literature, it is found that the reaction might proceed via Wittig/cyclic condensation/radical alkylation processes.