Atom-economic amide synthesis by using an iron-substituted polyoxometalate catalyst

Abstract

We report an efficient and economical amidation strategy by using polyoxometalate-based iron catalyst afford the corresponding amide products in good yields. All of the aliphatic, aromatic and heterocyclic substrates are...

Zirconium oxo clusters as discrete molecular catalysts for the direct amide bond formation

“…[18][19][20][21] In this context, we demonstrate herein that ZrOC can be developed into efficient catalysts by using the discrete dodecanuclear Zr-oxo cluster [Zr 6 IJOH) 4 O 4 IJOAcr) 12 ] 2 (OAcr = acrylate) (Zr 12 ) as a catalyst for the direct amide bond formations. [22][23][24][25][26][27] Catalytic amide bond formation [28][29][30][31][32][33][34][35][36][37] by direct condensation of non-activated carboxylic acids and amines is among the most relevant reactions enabled by Zr catalysts, [38][39][40][41] given their favorable atom economy compared to the amide coupling reagents, [42][43][44][45][46][47][48] and the ready availability of carboxylic acid and amine substrates. [22][23][24][49][50][51][52] However, recent promising advances in metal catalysts are still challenged by the catalyst overall stability, and its tolerance to the water formed as the reaction by-product.…”

On the Use of Triarylsilanols as Catalysts for Direct Amidation of Carboxylic Acids

“…There are very few reports on high-yielding catalytic amidation reactions of aromatic carboxylic acids in the ideal 1:1 acid/amine stoichiometry in the literature, − and perhaps unsurprisingly, catalytic quantities of bromosilanol 6h failed to provide any quantities of amides 3f–3h , which are among the most difficult combinations of acid and amine (Figure ). Pleasingly, some activity was found for the formation of aromatic amide 3e albeit in low conversion after 24 h. Aliphatic amide 3a was formed in quantitative yield in a reaction time of 6 h, albeit where the background reaction is itself complete in 24 h. This result demonstrates the need to run background reactions when reporting direct amidation reactions.…”

“…However, while there are several reports of successful silicon-based reagents and silica gels for direct amidation, there are no examples of silicon-centered molecular catalysts for direct amidations . Furthermore, while various proposals for the mechanistic operation of catalytic amidations have been moot, − only limited direct experimental evidence for presumed activated intermediates has been garnered . Herein, we report on the discovery, synthesis, and use of various electronically differentiated triarylsilanols as the first silicon-centered molecular catalysts for direct amidation.…”

“…The catalytic amidation of carboxylic acids thereby avoiding stoichiometric quantities of activating agent is the focus of much current research . Significant progress has been made with the development of boron-based catalysts, − oxophilic metal catalysts, and other catalytic systems . However, while there are several reports of successful silicon-based reagents and silica gels for direct amidation, there are no examples of silicon-centered molecular catalysts for direct amidations .…”

A Systematic Crystallographic Study of the Host–Guest Interactions between Amines and Ti8 Polyoxotitanium Clusters

“…They can either form H-bonds or react to yield amides. 39,40 Surprisingly, we captured both modes in one Ti 8 cluster when a diamine, 1,4-diaminobutane (DAB), was used in place of n-butylamine. The overall structure of Ti 8 O 10 (OOCPh) 16 ).…”