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Updated: May 23, 2026

Metal-free Synthesis of Ynones from Acyl Chlorides and Potassium Alkynyltrifluoroborate Salts
Published on: February 24, 2015
Application of metal-free conditions to a one-pot Leimgruber-Batcho indole synthesis
Beate Halsvik1, Bengt Erik Haug1
1University of Bergen, Department of Chemistry and Centre for Pharmacy Allégaten 41 5020 Bergen Norway bengt-erik.haug@uib.no.
Abstract:
A metal-free, one-pot synthesis of 2,3-unsubstituted indoles via an adapted Leimgruber-Batcho protocol has been developed. The process incorporates a chemoselective reduction of an aromatic nitro group using tetrahydroxydiboron and 4,4'-bipyridine, enabling efficient access to indole scaffolds under mild conditions. Application of this method resulted in comparable or improved yields relative to existing metal-based protocols. The successful preparation of 6-bromo-5-methoxyindole, a key constituent of breitfussin C, G, and H, shows the utility of this method for the synthesis of indoles relevant to natural product synthesis.
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