Hydrophilic Iridium Bis-N-Heterocyclic Carbene Complexes Catalyze Linear-Selective, Additive-Free Hydroaminomethylation of Long-Chain Olefins in Water

Abstract

Aqueous hydroaminomethylation (HAM) of olefins generally requires the use of organic solvents, additives, and high-pressure hydrogen to synthesize amines in satisfactory yields and selectivity. Herein, we accomplish the HAM reactions of long-chain olefins in water without organic solvent or additives by using a hydrophilic bis-NHC-Ir complex as the catalyst. A broad scope of long-chain olefins and amines is well compatible, affording corresponding higher amines in up to 99% yields with excellent linear/branched (l/b) selectivity (up to 94/6). Mechanistic investigations reveal that water acts as both solvent and hydrogen source. The protocol can be readily extended to the synthesis of pharmaceuticals and deuterated analogues with excellent yields and deuterium rates. Moreover, the amine products are easily separated by extraction, and the recovered aqueous phase could be directly used and recycled. This protocol offers a sustainable, safe, and cost-effective approach for synthesizing higher amines.