Highly-efficient N-arylation of imidazole catalyzed by Cu(II) complexes with quaternary ammonium-functionalized 2-acetylpyridine acylhydrazone

Synthesis, Characterization, Catalytic Activity, and DFT Calculations of Zn(II) Hydrazone Complexes

“…Hydrazone ligands are one of the most important classes of flexible and versatile polydentate ligands which show very high efficiency in chelating various metal ions [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. The coordination behavior of hydrazones is known to depend on the pH of the medium, the nature of the substituents and on the position of the hydrazone group relative to other moieties [ 2 , 3 , 4 ].…”

“…Moreover, deprotonation of the –NH group, which is readily achieved in the complexed ligand in particular, results in the formation of tautomeric anionic species (=N–N − –C=O or =N–N=C–O − ), having different coordination properties. Our interest in metal complexes with hydrazone-based ligands is partly due to their potential applications as catalysts [ 5 , 6 ] and molecular magnets [ 7 ]. Hydrazone ligands, obtained from Girard’s T reagent (trimethylammoniumacetohydrazide chloride) and 2-acetylpyridine or 2-quinolinecarboxaldehyde ( HL 3 Cl = ( E )- N , N , N -trimethyl-2-oxo-2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)ethan-1-aminium chloride and HL 4 Cl = ( E )- N , N , N -trimethyl-2-oxo-2-(2-(quinolin-2-ylmethylene)hydrazinyl)ethan-1-aminium chloride) are tridentate ligands which show the potential to form mononuclear and binuclear structures with metal ions [ 3 , 4 , 6 , 8 , 9 , 10 ].…”

“…Our interest in metal complexes with hydrazone-based ligands is partly due to their potential applications as catalysts [ 5 , 6 ] and molecular magnets [ 7 ]. Hydrazone ligands, obtained from Girard’s T reagent (trimethylammoniumacetohydrazide chloride) and 2-acetylpyridine or 2-quinolinecarboxaldehyde ( HL 3 Cl = ( E )- N , N , N -trimethyl-2-oxo-2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)ethan-1-aminium chloride and HL 4 Cl = ( E )- N , N , N -trimethyl-2-oxo-2-(2-(quinolin-2-ylmethylene)hydrazinyl)ethan-1-aminium chloride) are tridentate ligands which show the potential to form mononuclear and binuclear structures with metal ions [ 3 , 4 , 6 , 8 , 9 , 10 ]. In the mononuclear complexes (e.g., [Zn L 3 (NCS) 2 ] ( 3 ) [ 8 ], [Cd HL 3 (NCS) 2 (SCN)] [ 8 ], [Zn L 4 (N 3 ) 2 ] [ 9 ], [Zn L 4 (NCO) 2 ] [ 9 ], [Zn L 4 (N 3 ) 1.65 Cl 0.35 ] [ 10 ], [Cd L 4 (NCO) 1.64 Cl 0.36 ] [ 10 ] and [Co HL 4 (N 3 ) 3 ] [ 4 ]) with one hydrazone ligand being coordinated in a tridentate fashion to the central metal ion, the vacant coordination sites are filled by monodentate ligands (pseudohalides/halides) and in some cases by counter anions of starting metal salts [ 11 ].…”

“…In the other type of mononuclear structures two hydrazone ligand molecules occupy the coordination sphere of the central metal ion forming an octahedral coordination geometry (e.g., [Co L 3 2 ][Co(NCS) 4 ]BF 4 [ 12 ] and Zn(II) complex with the 2-acetylthiazole (N4)-phenylthiosemicarbazone ligand (CCDC 1059843) [ 13 ]). In the binuclear [M 2 ( L 4 ) 2 ( μ 1,1 -N 3 ) 2 (N 3 ) 2 ]⋅H 2 O⋅CH 3 OH (M = Ni(II) and Co(II)) [ 3 , 4 ] and [Cu 2 ( L 3 ) 2 ( μ 1,1 -N 3 ) 2 ](ClO 4 ) 2 [ 6 ] complexes, the hydrazone-based ligands show the same tridentate N , N , O -coordination mode forming the octahedral structure in the former two complexes cooperatively with two bridging and one terminal azide anion per metallic center and the square pyramidal in the latter with two bridging azides.…”

A Chemoselective and Desulfurative Chan–Lam Coupling: C–N Bond Formation between Benzimidazoline‐2‐Thiones and Arylboronic Acids

“…Several strategies have been developed for the synthesis of N ‐arylbenzimidazoles (Scheme ). Synthetic protocols that afford N ‐arylbenzimidazoles generally involve transition‐metal‐catalyzed Ullmann‐type cross‐couplings between benzimidazoles and aryl halides (Scheme a), intramolecular cross coupling of aromatic o ‐diamines with CO 2 (Scheme b), or cyclization of aromatic o ‐diamines with CO 2 and H 2 (Scheme c) . In addition, N ‐arylation of azole compounds using reactive and selective TMP‐iodonium(III) salts (Scheme d), and copper‐catalyzed couplings of N–H substrates with NaBPh 4 (Scheme e) are also optional pathways .…”