Regiospecific Minisci acylation of phenanthridine via thermolysis or photolysis

In this study, a new type of Minisci reaction for regiospecific acylation of phenanthridine has been developed based on cross dehydrogenative coupling (CDC) strategy. Using substoichiometric amount of TBAB (tetrabutylammonium bromide, 30 mol %) and K2S2O8 as an oxidant, acyl radicals generate from aldehyde substrates under thermal conditions followed by a regiospecific intermolecular acylation with phenanthridine. Furthermore, a preliminary research has indicated that the acylation reaction can be carried out at room temperature when K2S2O8/TBAB is displaced by (NH4)2S2O8 and another 5 mol % of fac-Ir(ppy)3 is used as photocatalyst under irradiation of visible light. This intermolecular acylation reaction provides an easy access to 6-acylated phenanthridine derivatives.

Graphical abstractUsing K2S2O8 as oxidant and TBAB as initiator, acyl radicals generate from aldehyde substrates and couple with phenanthridine under thermal conditions at 110 °C. When K2S2O8/TBAB is displaced by (NH4)2S2O8 and another 5 mol % fac-Ir(ppy)3 catalyst is added to the reaction system, this type of coupling reaction proceeds slowly under visible light at room temperature.Figure optionsDownload full-size imageDownload as PowerPoint slide