title: Benzimidazole and related ligands for Cu-catalyzed azide-alkyne cycloaddition.
abstract: Tris(2-benzimidazolylmethyl)amines have been found to be superior accelerating ligands for the copper(I)-catalyzed azide-alkyne cycloaddition reaction. Candidates bearing different benzimidazole N-substituents as well as benzothiazole and pyridyl ligand arms were evaluated by absolute rate measurements under relatively dilute conditions by aliquot quenching kinetics and by relative rate measurements under concentrated conditions by reaction calorimetry. Benzimidazole-based ligands with pendant alkylcarboxylate arms proved to be advantageous in the latter case. The catalyst system was shown to involve more than one active species, providing a complex response to changes in pH and buffer salts and the persistence of high catalytic rate in the presence of high concentrations of coordinating ligands. The water-soluble ligand (BimC4A)3 was found to be especially convenient for the rapid and high-yielding synthesis of several functionalized triazoles with 0.01-0.5 mol % Cu.
authors.affiliation: Department of Chemistry and The Skaggs Institute of Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
authors.forename: Valentin O
authors.initials: VO
authors.lastname: Rodionov
authors.forename: Stanislav I
authors.initials: SI
authors.lastname: Presolski
authors.forename: Sean
authors.initials: S
authors.lastname: Gardinier
authors.forename: Yeon-Hee
authors.initials: YH
authors.lastname: Lim
authors.forename: M G
authors.initials: MG
authors.lastname: Finn
mesh_terms: D000480:Alkynes / Q000737:chemistry; D001386:Azides / Q000737:chemistry; D001562:Benzimidazoles / Q000737:chemistry*; D002021:Buffers; D002151:Calorimetry / Q000379:methods; D002384:Catalysis; D002625:Chemistry, Organic / Q000379:methods*; D003300:Copper / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008024:Ligands; D008956:Models, Chemical; D015394:Molecular Structure; D013997:Time Factors; D014230:Triazoles / Q000737:chemistry
chemical_list: D000480:Alkynes; D001386:Azides; D001562:Benzimidazoles; D002021:Buffers; D008024:Ligands; D014230:Triazoles; D003300:Copper