Efficient and selective N-alkylation of amines with alcohols catalysed by manganese pincer complexes

Abstract

Borrowing hydrogen (or hydrogen autotransfer) reactions represent straightforward and sustainable C–N bond-forming processes. In general, precious metal-based catalysts are employed for this effective transformation. In recent years, the use of earth abundant and cheap non-noble metal catalysts for this process attracted considerable attention in the scientific community. Here we show that the selective N-alkylation of amines with alcohols can be catalysed by defined PNP manganese pincer complexes. A variety of substituted anilines are monoalkylated with different (hetero)aromatic and aliphatic alcohols even in the presence of other sensitive reducible functional groups. As a special highlight, we report the chemoselective monomethylation of primary amines using methanol under mild conditions.

Amination of isopropanol to isopropylamine over a highly basic and active Ni/LaAlSiO catalyst

“…The ammonolysis process can be applied for the conversion of many raw materials such as carboxylic acids, a-olefins, alkyl halides, aldehydes, ketones and alcohols to amines [8][9][10][11], among which alcohols are abundant and the ammonolysis process of alcohols with ammonia to amines appears environmentally benign, safe and selective [12]. Thus, the ammonolysis of alcohols is becoming more and more important for the industrial synthesis of aliphatic amines [13,14].…”

Transition‐Metal‐Catalyzed Utilization of Methanol as a C1 Source in Organic Synthesis

“…In this regard, Beller and co-workers [37] have developed ac atalyst system based on earth-abundant manganese for the N-methylation of amines using methanol as the methylating agent (Scheme 14). In this regard, Beller and co-workers [37] have developed ac atalyst system based on earth-abundant manganese for the N-methylation of amines using methanol as the methylating agent (Scheme 14).…”

Efficient Cobalt‐Catalyzed Methylation of Amines Using Methanol

“…[1,5] N-methylation of amines using methanol is a promising green and sustainable method for synthesis of N-methylamines with H 2 O as the only byproduct. [12] Up to now, methylation of amines with methanol has been achieved over expensive and rare second/third-row transition-metal catalysts such as homogeneous Ru [13][14][15] and Ir [16][17] complex, and heterogeneous Lewis acid catalysts under harsh reaction conditions (> 240 8C). [11] Apparently, the energy barrier to the activation of smaller alcohols appeared to be too uphill.…”

“…[11] Apparently, the energy barrier to the activation of smaller alcohols appeared to be too uphill. Although N-alkylation of amines or C-alkylation of ketones with higher alcohols has been realized taking Fe, [19] Co, [20][21][22][23][24][25][26] Mg [12] and Mn [27] complexes in the presence of base, ligands or other additives, methanol was scarcely utilized in these catalytic systems. [18] The replacement of the scarce and expensive noble metals by cheaper, more abundant and less toxic first-row transition metals, such as iron or cobalt, is of significance from the view point of the sustainable development.…”

“…Co ( [11][12][13][14][15][16]. The yield of 2 a was decreased from > 99% to 77% when Na 3 PO 4 was used in stead of K 3 PO 4 , probably owing to the decreased basicity (entry 6 vs. 11).…”