Copper‐NHC Based Ullmann Catalysis in Water for Selective N‐Arylation of 3‐Aminophenols

Abstract

Studies of environmentally benign catalytic methods are of great value in modern chemical synthesis, especially the chemo‐selective construction of chemical bonds under green conditions. This work elucidates such preferential synthesis of C−N bond over C−O bond via selective N‐arylation of 3‐aminophenols using 1,3‐bis‐[2‐hydroxyphenyl] imidazolium chloride (IHPHCl) and copper iodide as catalyst (1 mol %) in aqueous medium. Presence of chelating group (−OH) on IHPHCl enhances N‐selectivity. Overall this is a simple and green method for selective N‐arylation of 3‐aminophenols with good substrate scope and yields (60–88 %). GC‐MS, HRMS and other spectroscopic techniques were utilised in detailing the kinetics and mechanistic aspects.

Benzilbis(2-hydroxyanil) – highly efficient ligand for ferric ion (Fe3+) sensing

“…23 Despite numerous reports for the sensing of iron, turn-on probes that can selectively sense Fe 3+ ions in the presence of Fe 2+ are relatively limited. During our prior studies on 1,3-imidazolium salts 24,25 as ligands in cross-coupling reactions, a-diimines were prepared as imidazolium precursors. Upon photo-physical characterization, one of the a-diimines, i.e., benzilbis(2-hydroxyanil) (L) was found to be a potential candidate for sensing studies.…”

Non‐Symmetrical Tetraaryl‐α‐Diimines via Transimination: A Promising Route for Non‐Symmetrical 1,3,4,5‐Tetraarylimidazolium Chlorides

“…To overcome this synthetically challenging aspect, we have developed a simple transimination route for the preparation of non-symmetrical tetraaryl α-diimines (ArÀ N=C(Ph)À C(Ph)=NÀ Ar'), where two different aryl units (Ar and Ar') were bonded to the imine nitrogen atoms. In continuation to our previous studies on 1,3-imidazolium based NHCs, [29,30] this work focuses on the synthesis and studies of new non-symmetrical tetraaryl α-diimines and the corresponding non-symmetrical tetraaryl NHC precursors.…”