N-Heterocyclic Carbenes in Iron-Catalyzed Cross-Coupling Reactions

1. N-Heterocyclic Carbenes in Iron-Catalyzed Cross-Coupling Reactions Marc C. Perry, Department of Chemistry, University of Alaska Anchorage Although the iron-catalyzed cross-coupling of aryl chlorides and alkyl Grignards has received significant attention, there are still some challenges that need to be addressed in order to broaden the scope of the types of substrates that can be used. Currently, there is no good method for the general cross-coupling of secondary alkyl Grignards, and successful cross-couplings of unactivated aryl chlorides have not been reported. We investigated the use of N-heterocyclic carbenes as ligands in the iron-catalyzed cross-coupling of unactivated aryl chlorides with alkyl Grignard reagents. We found that primary Grignard reagents coupled in high yields even with highly electron rich aryl chlorides while secondary alkyl Grignard reagents coupled in low yields with moderate branched to linear ratios. FeCl2 (5 mol%) THF, 70 0C NHC(10 mol%) Primary Grignard Secondary Grignard