Supported Cu^II Single‐Ion Catalyst for Total Carbon Utilization of C₂ and C₃ Biomass‐Based Platform Molecules in the N‐Formylation of Amines

Abstract

The shift from fossil carbon sources to renewable ones is vital for developing sustainable chemical processes to produce valuable chemicals. In this work, value‐added formamides were synthesized in good yields by the reaction of amines with C2 and C3 biomass‐based platform molecules such as glycolic acid, 1,3‐dihydroxyacetone and glyceraldehyde. These feedstocks were selectively converted by catalysts based on Cu‐containing zeolite 5A through the in situ formation of carbonyl‐containing intermediates. To the best of our knowledge, this is the first example in which all the carbon atoms in biomass‐based feedstocks could be amidated to produce formamide. Combined catalyst characterization results revealed preferably single CuII sites on the surface of Cu/5A, some of which form small clusters, but without direct linking via oxygen bridges. By combining the results of electron paramagnetic resonance (EPR) spin‐trapping, operando attenuated total reflection (ATR) IR spectroscopy and control experiments, it was found that the formation of formamides might involve a HCOOH‐like intermediate and .NHPh radicals, in which the selective formation of .OOH radicals might play a key role.

Highly Selective Catalyst‐Free Oxidative Synthesis of N‐Formamides from C2‐ and C3‐Feedstocks

“…This N-based radical species or * OH radicals from TBHP breaks down DHA to provides two 2 * CH 2 OH species, which couples with N-based radicals and further oxidation by TBHP to give 2 moles of Nformamide product. [22] The tert-butoxide radical from TBHP can also abstract * H radicals to form tert-butyl alcohol as the byproduct. [27] This is also supported by the fact that the CS: amine ratio was maintained at 1 : 2 throughout the optimization and control experiments, so for complete conversion of 2 molecules of aniline to N-formamide product, 2 carbons from the molecular skeleton of DHA most possibly be participating in the formation of desired product.…”

“…These radicals react with 2 molecules of amine to form N‐based radical species. This N‐based radical species or ⋅OH radicals from TBHP breaks down DHA to provides two 2 ⋅CH 2 OH species, which couples with N‐based radicals and further oxidation by TBHP to give 2 moles of N ‐formamide product [22] . The tert ‐butoxide radical from TBHP can also abstract ⋅H radicals to form tert ‐butyl alcohol as the by‐product [27] .…”

“…They also showed application of DHA, GLYAC, glyceraldehyde as feedstocks for conversion of amines to N-formamides using Cu supported on 5 A zeolite. [22] These are significant reports as the application of these bio-sourced feedstocks as a building block for synthesis of formamides opens the multiple possibilities of these feedstocks and other molecules being explored as unique fragmented building blocks in syntheses of other high value chemicals.…”

Cu-Catalysed sustainable synthesis of formamide with glycerol derivatives as a carbonyl source via a radical-relay mechanism

“…In this case, the C–C bond in GA was split off to form carbonyl-containing intermediates in situ . 52 Since GA must first be formed by the oxidation of DHA, it would be much more attractive to use DHA right away as a carbonyl source for formamide synthesis. Indeed, we could show that with a supported Cu/Al 2 O 3 catalyst, DHA and various amines can be converted to the corresponding formamides in high yields even at room temperature.…”

“…It is known that H 2 O 2 is split by Cu-based catalysts in a Fenton-like reaction into ˙OH and ˙OOH radicals. 47,52,59 Usually ˙OH radicals dominate but the specific radical ratio depends on the electronic properties of the Cu centres since high electron density promotes the formation of ˙OH radicals (eqn (1) and (2)). 59 Cu II + H 2 O 2 → Cu I + ˙OOH + H + Cu I + H 2 O 2 → Cu II + ˙OH + OH − …”