Copper-Catalyzed Huisgen [3 + 2] Cycloaddition of Gold(I) Alkynyls with Benzyl Azide. Syntheses, Structures, and Optical Properties

Abstract

The copper(I)-catalyzed Huisgen [3 þ 2] cycloaddition is a general reaction encompassing wide ranges of organoazide and primarily terminal alkyne reacting partners. Strained internal alkynes can also undergo cycloaddition with azides. We report here that tetrakis(acetonitrile)copper(I) hexafluorophosphate catalyzes the [3 þ 2] cycloaddition of (phosphine)-and (N-heterocyclic carbene)gold(I) alkynyls with benzyl azide. Isolated yields of up to 96% result. The reaction protocol broadly tolerates functionalities on the alkynyl reagent. Gold(I) triazolate products form with complete 1,4-regioselectivity. Some 15 new gold(I) triazolates are reported along with crystal structures of nine. Triazolate complexes bearing polycyclic aromatic substituents show dual singlet-and triplet-state luminescence from excited states localized on the aromatic fragment. Time-resolved emission experiments find long lifetimes consistent with triplet emission parentage. Absorption and emission transitions are analyzed with time-dependent density-functional theory calculations.

The First Well‐Defined Silver(I)‐Complex‐Catalyzed Cycloaddition of Azides onto Terminal Alkynes at Room Temperature

“…While gold(I),7a silver(I)6d, 7c and other7b acetylides are known to participate in the AAC reaction, the addition of copper(I) salts is required to effect the cycloaddition, in accord with the π‐complexation step. No competent silver(I) or gold (I) species has been reported to catalyze the catalytic cycle alone, and several failed attempts at copper‐free AAC reactions with silver acetylides have been reported (Scheme ).…”

Au-iClick mirrors the mechanism of copper catalyzed azide–alkyne cycloaddition (CuAAC)

“…[2][3][4] Others [5][6][7] extended iClick to include the already prevalent [8][9] cycloaddition of an organic substrate to either a metal-azide or metal-acetylide. 7,[10][11][12][13][14][15][16][17][18][19][20][21] Important to this work, Gray et al 22 demonstrated that gold-acetylides and gold-azides will undergo cycloaddition to their organic counterparts. Despite the fact that several transition metals other than Cu(I) catalyze the azide-alkyne cycloaddition, including ruthenium, silver, and iridium, [23][24][25][26] it became apparent that not all metal-acetylide/azide species will participate in the iClick cycloaddition.…”

Organogold oligomers: exploiting iClick and aurophilic cluster formation to prepare solution stable Au4 repeating units

“…6 Critical in the pursuit of building complexity is the precise control of bond forming events and is particularly exemplified by the Cu I catalyzed azide-alkyne cycloaddition reaction (CuAAC). Others [11][12][13] have broadened the iClick concept to include the cycloaddition of organic substrates to either a metal-azide or metal-acetylide (M; Scheme 1), which are already rather prevalent reactions, [13][14][15][16][17][18][19][20][21][22][23][24][25] and the subject of reviews. The metal-azide/metal-acetylide cycloaddition (M-M′) was given the term inorganic click (iClick) as a distinguishing feature that calls attention to chemistry occurring within the coordination sphere of a metal ion.…”