An Efficient A³ Coupling Catalyst Based on a Silver Complex Bearing N‐Heterocyclic Carbene and Homoscorpionate Bis(3‐methyl‐mercaptoimidazolyl)borate Ligands

Abstract

Reaction of Ag(IPr)(Cl), 1 [IPr=1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene] with sodium precursors Na(mim) [mim=dihydrobis(methimazolyl)borate] and Na(Bb) [Bb=dihydrobis(2‐mercapto‐benzothiazolyl)borate] formed two novel silver complexes [Ag(IPr)(mim)], 2 and [Ag(IPr)(Bb)], 3. These complexes catalyzed three‐component coupling reaction of a series of aldehydes with alkynes and amines. The efficiency of these novel catalysts compared with that of 1 and Au(IPr)(Cl), 4.

Silver Nanoparticle-Incorporated Defect-Engineered Zr-based Metal–Organic Framework for Efficient Multicomponent Catalytic Reactions

“…The mechanism of A 3 coupling is assumed to proceed through the C–H activation of the alkyne by Ag@UiO-66-SH, based on the reported mechanistic studies from the literature. , Since no base is used in this procedure, unlike classical synthetic techniques, observation of first-order kinetics led us to believe that the formation of the silver–alkynylide intermediate is the rate-determining step of the reaction. This intermediate reacts with the iminium ion generated in situ from aldehydes and secondary amines to produce the respective propargylamine and regenerate the catalyst for recyclability (Scheme S2).…”

Catalytic exploration of NHC–Ag(i)HMDS complexes for the hydroboration and hydrosilylation of carbonyl compounds

“…8 Finally, upon examination of the mean plane in the isostructural solid-state structures of 3 and 4 we note that the amide is planar corresponding to the Ag centre for 3 (5.993°) and coplanar for 4 (87.885°). Examination of the 1 H and 13 C NMR spectra of 3 and 4 in C 6 D 6 solvent confirm the Ag(I) amide complexes retain their structure in solution. Characteristic of NHC silver(I) complexes, 43 the 13 C NMR spectrum reveals typical carbene carbon signals of two doublets displaced in high chemical shifts, around δ = 187 ppm for 3 and significantly further upfield for 4 at δ = 177 ppm (Fig.…”

“…6 Focusing on silver(I)-NHC complexes, their synthetic versatility and application in a wide range of catalytic and organic transformations including A 3 coupling, alkynylation, CO 2 insertions and cyclisation reactions makes them useful reagents in synthesis. [11][12][13][14][15][16][17][18][19] A key aspect to this diverse reactivity is the ease of modularity of the ancillary NHC ligand which can alter its steric and electronic character via modification of the backbone and/or the substituents attached to the N atoms of the azole ring. [20][21][22][23][24] By exploiting the tuneability of NHC ligands, Takaki and co-workers developed a potent silver(I)-NHC pre-catalyst [AgCl(IMes)] (IMes = 1,3-bis(2,4,6-trimethylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene) that allowed β-selective hydroboration of alkynes and allenes to give direct access to a diverse range of organoboron compounds (Scheme 1c).…”

Synthesis and Application of Silylene-Stabilized Low-Coordinate Ag(I)–Arene Cationic Complexes

“…Concurrently, the amine and aldehyde react together to form I3 . The Δ E and Δ G for this reaction are −9.3 and 2.8 kcal/mol, respectively . The C–O bond length in I3 (1.47 Å) is longer than the C–O bond length in alcohol (in the range of 1.41–1.43 Å), facilitating proton abstraction by coupling with I2 , resulting in the formation of I4 .…”