New efficient ligand for sub-mol % copper-catalyzed C–N cross-coupling reactions running under air

Abstract

SummaryA new efficient ligand, N,N’’-dimethyldiethylene triamine (DMDETA), has been synthesized and evaluated for sub-mol % copper-catalyzed C–N cross-coupling reactions. The efficiency of the ligand was determined by kinetic methods. DMDETA proved to display efficiency similar to DMEDA and, in addition, the resulting catalyst was tolerant to air.

Origins of high catalyst loading in copper(i)-catalysed Ullmann–Goldberg C–N coupling reactions

“… 22 , 35 More recent studies by Davies and co-workers identified even more nuances in the role of the O , O -chelating ligand 2-acetylcyclohexanone, which is easily displaced by the malonate anion (included as a base), and the formation of di-, tri-, and tetrameric Cu( i )-amido species. 29 , 30 The high catalyst/ligand loading (typically 10 mol% of Cu( i ) precursor and 20 mol% of ligand; reactions with a catalyst loading below 1 mol% are rare), 36 , 37 its poor reproducibility, 38 and the need for aryl iodide/bromide substrates remain important challenges in these reactions.…”

New Insights into the Reaction Capabilities of Ionic Organic Bases in Cu‐Catalyzed Amination

“…One of the main practical challenges facing the Ullmann reaction is the requirement for high copper catalyst loadings (< 5 mol‐% is rare). Nevertheless, recent work carried out in the groups of Norrby, Ling, Jiang and Ma have shown that the use of sub‐mol % Cu loadings in the Ullmann amination reaction is achievable in some situations . However, these reactions still required either high loadings of auxiliary ligand (10–20 mol‐% DMEDA), or elevated reaction temperatures (50–135 °C) , …”

“…Most screening studies reported to date with organic base promoted transition metal‐catalyzed processes (Cu, Pd or Ni) have focused on simple primary and secondary amines , . Coupling of more challenging amines with aryl halides under sub‐mol % conditions either gave very poor reaction yields or were not reported during substrate scope studies , , , . Attempts to improve the reactivity of these challenging amines in sub‐mol % copper‐catalyzed reactions have yet to be reported.…”

Synthesis of 5‐Substituted Benzo[h]quinoline Derivatives via Reactions Involving C(sp2)−Br Bond Activation

“…In order to avoid the occurrence of undesirable processes, we decided to carry out the phenoxylation reaction at a higher temperature but for a shorter time. Therefore, at this point, we examined the catalytic method described in literature, in which copper(I) halides were successfully used as catalysts in O ‐arylation of phenol in an NMP environment . The model reaction system used for optimization consisted of various loadings of copper(I) chloride, 1.3 eq of phenol and 1.1 eq of cesium carbonate (Scheme ), as reported.…”