F-tag induced acyl shift in the photochemical cyclization of o-alkynylated N-alkyl-N-acylamides to indoles

Abstract

A photochemical cyclization of F-tagged, o-alkynylated N-alkylamides to indoles catalyzed by the [Ir(dtbbpy)(ppy)2]PF6 is presented. This straightforward and efficient reaction involves an intramolecular rearrangement due to the presence of fluorine in the acyl moiety and is the first example of photochemically induced 1,3-acyl shift in the cyclization towards 3-acylidoles. A four-step reaction sequence to the desired derivatives including the photoreaction as a key step has been developed and optimized. The compatibility of differently substituted F-tagged precursors with the photocyclization step was investigated and the robustness of this step towards modifications could be shown. In total, 19 so far unknown derivatives with diverse modifications in positions N1 and C2 were synthesized in very good yields and fully characterized.