Kyohei Ozaki, Hua Zhang, Hideto Ito, Aiwen Lei, and Kenichiro Itami

Chem. Sci. 2013, 4, 3416–3420, DOI: 10.1039/C3SC51447A

We have developed a Pd-Cu-Ag trimetallic system that can convert indoles to carbozoles using electrondeficient alkenes as two-carbon units. Investigation of reaction mechanism revealed that this one-shot indole-to-carbozole π-extension is likely to proceed through the sequence of (i) Pd/Cu-catalyzed indole C–H alkenylation, (ii) Ag-promoted Diels–Alder reaction and
dehydrogenative aromatization. The 10 successful one-pot synthesis of granulatimide derivative, an interesting class of Chk1 kinase inhibitor, highlights the potential of the present reaction for further development and applications.