Ligand-Free Copper-Catalyzed Negishi Cross-Coupling
Ligand-Free Copper-Catalyzed Negishi Coupling of Alkyl-, Aryl-, and Alkynylzinc Reagents with Heteroaryl Iodides.
Angew. Chem. Int. Ed. 2015;
20 July 2015 (online)
A ligand-free, copper-catalyzed Negishi cross-coupling of various zinc reagents with heteroaryl iodides affording the desired coupling products in very high yields is reported. The reaction proceeds within three hours at room temperature for alkylzinc reagents; however, higher temperatures are required for coupling with aryl- and alkynylzinc reagents.
Interestingly, no β-hydride elimination or rearrangement was observed for the coupling with primary, secondary, or tertiary alkylzinc reagents. Moreover, a variety of functional groups are tolerated in this protocol.