An efficient N-heterocyclic carbene based ruthenium-catalyst: Application towards the synthesis of esters and amides

Landgang

“…Even though the amount of deposited silver (2–3 at %) was higher compared to that of ruthenium (0.25–2 at %), use of the latter resulted in almost twice as much conversion (Figure 4) indicating that the Ru‐npAu combination was preferable for amide bond formation. With respect to the ruthenium complexes used in homogeneous catalysis, surface‐bound methoxy could only be formed on the metal if strong σ donor and weak π acceptor ligands were used to create an electron‐rich ruthenium center 11d. 25 An explanation for the higher catalytic activity of the Ru‐npAu‐material would thus involve a transfer of electron density from the gold substrate to the ruthenium,26 similar to the action of ligands in homogeneous ruthenium catalysts.…”

Atom-economic dehydrogenative amide synthesis via ruthenium catalysis

“…In addition, the reaction could be performed under neutral conditions without any additive. [25][26][27][28][29][30][31][32][33][34][35][36][37][38] Hong and co-workers reported Ru-NHC complexes 4a-4e for this reaction (as shown in Fig. 3b).…”

“…act as a stronger s-donor and weaker p-acceptor compared with its imidazolylidene analogs, was successfully synthesized by Möller et al 32 This complex is highly active for amidation of alcohols with amines in the presence of a catalytic amount of KOtBu (Fig. act as a stronger s-donor and weaker p-acceptor compared with its imidazolylidene analogs, was successfully synthesized by Möller et al 32 This complex is highly active for amidation of alcohols with amines in the presence of a catalytic amount of KOtBu (Fig.…”

Ruthenium-Catalyzed Amide-Bond Formation

“…Ruthenium complexes, and especially NHC-compounds, have been the most widely studied [94], albeit highly efficient processes promoted by rhodium or silver have also been described [112,113]. In regard to ruthenium, both in-situ-generated catalytic systems (Table 1) [114][115][116][117][118][119][120][121][122][123] as well as well-defined catalysts 38-44 ( Figure 10) [124][125][126][127][128][129][130][131] have been reported. In most of the cases, high metal loadings (usually 5 mol%) and an excess of a strong base (10-40 mol% of NaH or KO-t-Bu) were required to achieve satisfactory yields in the amides.…”