Selective Iron-Catalyzed N-Formylation of Amines using Dihydrogen and Carbon Dioxide

Abstract

A family of iron(II) carbonyl hydride species supported by PNP pincer ligands was identified as highly productive catalysts for the N-formylation of amines via CO 2 hydrogenation. Specifically, iron complexes supported by two different types of PNP ligands were examined for formamide production. Complexes containing a PNP ligand with a tertiary amine afforded superior turnover numbers in comparison to complexes containing a bifunctional PNP ligand with a secondary amine, indicating that bifunctional motifs are not required for catalysis. Systems incorporating a tertiary amine containing a PNP ligand were active for the N-formylation of a variety of amine substrates, achieving TONs up to 8900 and conversions as high as 92%. Mechanistic experiments suggest that N-formylation occurs via an initial, reversible reduction of CO 2 to ammonium formate followed by dehydration to produce formamide. Several intermediates relevant to this reaction pathway, as well as ironcontaining deactivation species, were isolated and characterized.

Multi‐Step Reactions Involving Iron‐Catalysed Reduction and Hydrogen Borrowing Reactions

“…Conducting the transformation in THF at 120 °C for 4–16 h under 35 bar of CO 2 and 35 bar of H 2 , a huge variety of primary and secondary alkylamines were converted into the corresponding formates with 8–92 % yields and TONs up to 8900 . This value has to be compared to the ones obtained with PNN pincer Ru catalysts with TON up to 1940000 for the N‐ formylation of morpholine under similar conditions …”

Synthesis of pyrazolopyrimidines in mild conditions by gold nanoparticles supported on magnetic ionic gelation in aqueous solution

“…FeNi 3 core‐shell NPs have been used as suitable catalysts in many reactions, including the synthesis of 1,3‐thiazolidin‐4‐ones, [ 49 ] triazolo[1,2‐ a ]indazole‐triones, [ 50 ] and 4H‐benzo[b]pyrans. [ 51 ] Given our continued interest in nanocatalysis and catalyst development for organic reactions, [ 52–61 ] in this work we developed a facile synthesis of gold NPs supported on a magnetically separable IG‐based nanomaterial, FeNi 3 /IG/Au, at room temperature via a wet impregnation technique based on IG using TPP as the cross‐linking agent and FeNi 3 as the magnetic core to allow for magnetic separation. In addition, we describe its use in the synthesis of pyrazolopyrimidines, which could be easily separated from the reaction mixture for reuse (Scheme 1).…”

Selective synthesis of formamides, 1,2-bis(N-heterocyclic)ethanes and methylamines from cyclic amines and CO2/H2 catalyzed by an ionic liquid–Pd/C system

“…[1][2][3][4][5][6] The reactions of amines with CO 2 in the presence of reductants such as hydrosilanes and H 2 have been widely investigated, and they generally produce formamides or methylamines. [7][8][9][10][11] For the reaction of amines with CO 2 /H 2 , the production of methylamines is more difficult than the formation of formamides, [12][13][14][15][16][17] and it requires harsh reaction conditions and catalysts with very high activity. 18-21 1,2-Bis(N-heterocyclic)ethanes (e.g., 1,2-bis(piperidine)ethane) are a kind of high value chemical and are generally synthesized via the reaction of cyclic amines with ethyl halides, suffering from production of a large amount of acid waste and complicated post-treatment.…”