Tuning Chemoselectivity in Iron-Catalyzed Sonogashira-Type Reactions Using a Bisphosphine Ligand with Peripheral Steric Bulk: Selective Alkynylation of Nonactivated Alkyl Halides

摘要

Alkynes are important structural units of various bioactive molecules and organic electronic materials as well as of versatile intermediates in organic synthesis. We frequently rely on the Sonogashira reaction to incorporate alkynyl units into organic molecules in laboratory and industrial settings. Despite their prevalent use in the chemical synthesis, non-activated alkyl halides with β-hydrogen atoms have remained as difficult electrophiles for the cross-coupling reaction. Considerable efforts have been devoted to address this problem: Fu and co-workers recently employed a palladium/copper catalyst composite with a bulky N-heterocyclic carbene (NHC) ligand.