Using blue-light driven iron-catalysis to afford molecular diversity in phosphindole oxide derivatives.

We have developed original blue-light promoted iron-catalyzed reactions of activated alkynes with secondary phosphine oxides in the presence of tert-butylhydroperoxide under argon at room temperature. Depending on the nature of the iron precursors, benzo[b]phosphole oxides were obtained using Fe(NO3)3 in methanol and 9-phenyltribenzo[b,e,g]phosphindole 9-oxide derivatives utilizing Fe(OTf)2 in acetic acid. Control experiments revealed that radical processes are involved, permitting the proposal of a reasonable mechanism.