Room-temperature Pd/Ag direct arylation enabled by a radical pathway

• Amy L. Mayhugh and
• Christine K. Luscombe

Beilstein J. Org. Chem. 2020, 16, 384–390, doi:10.3762/bjoc.16.36

• to form hybrid palladium-radical intermediate 5. This carbon-centered radical can then add to the indole. From here, three different pathways to rearomatize 7 are possible, eventually affording the arylated product 10. Pd(0) can be regenerated by a base; in this case, the silver carboxylate. This

• room-temperature direct arylation reaction between indole and iodobenzene reported in ref. [12] and adapted in this work to study room-temperature DArP. Commonly discussed mechanisms for C2 selective direct arylation, none containing radical intermediates. Proposed mechanism for palladium radical

• -temperature, Pd/Ag-catalyzed direct arylation systems are radical-mediated. This is in contrast to the commonly proposed two-electron mechanisms for direct arylation and appears to extend to other substrates such as benzo[b]thiophene and pentafluorobenzene. Keywords: direct arylation; indole; palladium