Solvent-free Buchwald–Hartwig amination with low palladium loadings

A highly efficient ‘green’ solvent-free monoarylation of primary anilines with aryl bromides mediated by the expanded-ring N-heterocyclic carbene palladium complex (THP-Dipp)Pd(cinn)Cl [THP-Dipp is 1,3-bis(2,6-diisopropylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene; cinn is cinnamyl] can be performed at low catalyst loadings (0.1 mol%) to provide excellent yields and remarkable selectivities for various substrates.