Low‐Temperature N‐Alkylation of Amines with Alcohols in Protic Solvents Catalyzed by Iridium Complexes Bearing N‐Heterocyclic Carbenes

Amines are important compounds found in natural products, pharmaceuticals, and fine chemicals. Therefore, the development of elegant, environmentally friendly, and simple synthetic methods is desirable. Recently, the borrowing‐hydrogen (BH) strategy has received considerable attention for C–N bond formations because of its high atomic efficiency and the absence of toxic waste generation. Researchers have recently reported that the use of N‐heterocyclic carbene (NHC) ligands with strong electron‐donating properties and protic solvents can increase the catalytic activity in the BH strategy. Therefore, herein, we focused on the versatility of the synthetic methods, such as a synthetic system that allows simple synthesis, operates at low reaction temperatures, and involves the use of effective solvent simultaneously. The catalyzed N‐alkylation of alcohols and amines in protic solvents under mild conditions was investigated using simple NHC complexes developed by our group. We achieved the synthesis of various alkylamines under mild conditions, such as 40–60 °C, using iridium complexes comprising NHC ligands with simple structures and protic solvents such as 2,2,2‐trifluoroethanol and 1,1,1,3,3,3‐hexafluoroisopropanol.