Additive-free N-methylation of amines with methanol over supported iridium catalyst. Issue 10 (30th March 2021)

• Record Type: Journal Article
• Authors: Wang, Jing; Qiang, Wenwen; Ye, Sen; Zhu, Longfei; Liu, Xiang; Loh, Teck-Peng
• Is Part Of: Catalysis science & technology. Volume 11:Issue 10(2021)
• Page Start: 3364
• Page End: 3375
• Publication Date: 2021-03-30
• Subjects: Catalysis -- Periodicals; 541.395
• DOI: 10.1039/d0cy02442b
• Languages: English
• ISSNs: 2044-4753

Abstract

Abstract : Clean N -methylation of amines with methanol was achieved, providing a green approach to the selective synthesis of mono- or di-methylated amines. Abstract : An efficient and versatile zinc oxide-supported iridium (Ir/ZnO) catalyst was developed to catalyze the additive-free N -methylation of amines with methanol. Mechanistic studies suggested that the high catalytic reactivity is rooted in the small sizes (1.4 nm) of Ir nanoparticles and the high ratio (93%) of oxidized iridium species (IrO x, Ir 3+ and Ir 4+ ) on the catalyst. Moreover, the delicate cooperation between the IrO x and ZnO support also promoted its high reactivity. The selectivity of this catalytic N -methylation was controllable between dimethylation and monomethylation by carefully tuning the catalyst loading and reaction solvent. Specifically, neat methanol with high catalyst loading (2 mol% Ir) favored the formation of N, N -dimethylated amine, while the mesitylene/methanol mixture with low catalyst loading (0.5 mol% Ir) was prone to producing mono- N -methylated amines. An environmentally benign continuous flow system with a recycled mode was also developed for the efficient production of N -methylated amines. With optimal flow rates and amine concentrations, a variety of N -methylamines were produced with good to excellent yields in this Ir/ZnO-based flow system, providing a starting point for the clean and efficient production of N -methylamines with this cost-effective chemical process.