Expanding the Scope of Cu(I) Catalyzed “Click Chemistry” with Abnormal NHCs: Three-Fold Click to Tris-Triazoles

Abstract

Cationic copper(I) complexes [Cu(aIPr Ph )(IPr)]I (3) and [Cu(aIPr Ph ) 2 ]I (4) featuring an abnormal N-heterocyclic carbene (aNHC) (aIPr Ph = 1,3-bis(2,6-diisopropylphenyl)-2-phenylimidazol-4-ylidene) and/or an NHC (IPr = 1,3-Bis(2,6-diisopropylphenyl)imidazol-2-ylidene) ligand(s) are reported. Treatment of Cu(aIPr Ph )I (2) with IPr affords complex 3. Reaction of (IPrPh)I (1) (IPrPh = 1,3-bis(2,6-diisopropylphenyl)-2-phenyl-imidazolium) with CuI in the presence of K{N(SiMe 3 ) 2 } leads to the formation of 4. Complexes 3 and 4 represent rare examples of mixed aNHC-NHC and bis-aNHC metal complexes, respectively. They are characterized by elemental analysis, NMR spectroscopic, and mass spectrometric studies. The solid-state molecular structures of 3 and 4 have been determined by single crystal X-ray diffraction analyses. The catalytic activity of 2, 3, and 4 has been investigated in the [3+2] cycloaddition of alkynes and organic azides, affording triazole derivatives in an almost quantitative yield. Notably, complexes 2, 3, and 4 are excellent catalysts for the three-fold cycloaddition of a tris-azide with various alkynes. This catalytic protocol offers a high yield access to tris-triazoles in a shorter reaction time and considerably reduces the experimental work-up compared to the classical synthetic method.

Boosting the π‐Acceptor Property of Mesoionic Carbenes by Carbonylation with Carbon Monoxide

“…Consistent with the two‐coordinated Cu(I) compounds, 6 ‐Ph and 6 ‐Bp show a linear coordination geometry at the Cu(I) atom with the C2−Cu1−Cl1 and C7−Cu2−Cl2 bond angles of 176.1(1)°–176.8(1)°. The C2−Cu1 and C7−Cu2 bond lengths of 6 ‐Ph and 6 ‐Bp (1.882(1)–1.887(2) Å) are similar to those of known mononuclear Cu(I) complexes (iMIC)CuX (X=Cl, Br or I) (1.87–1.90 Å) [23–24,33] . The C2−Au1 1.980(6) Å and C7−Au2 1.983(6) Å bond lengths of 8 ‐Ph are in line with that of reported (iMIC)AuCl complexes (1.98–2.01 Å) [26]…”

“…The C2À Cu1 and C7À Cu2 bond lengths of 6-Ph and 6-Bp (1.882(1)-1.887(2) Å) are similar to those of known mononuclear Cu(I) complexes (iMIC)CuX (X = Cl, Br or I) (1.87-1.90 Å). [23][24]33] The C2À Au1 1.980(6) Å and C7À Au2 1.983(6) Å bond lengths of 8-Ph are in line with that of reported (iMIC)AuCl complexes (1.98-2.01 Å). [26]…”

Steigerung der π‐Akzeptoreigenschaft mesoionischer Carbene durch Carbonylierung mit Kohlenmonoxid

“…In Übereinstimmung mit zweifach koordinierten Cu(I)‐Verbindungen weisen 6 ‐Ph und 6 ‐Bp eine lineare Koordinationsgeometrie am Cu(I)‐Atom mit den Bindungswinkeln C2−Cu1−Cl1 und C7−Cu2−Cl2 von 176.1(1)°–176.8(1)° auf. Die C2−Cu1 und C7−Cu2 Bindungslängen von 6 ‐Ph und 6 ‐Bp (1.882(1)–1.887(2) Å) sind ähnlich zu bekannten einkernigen Cu(I)‐Komplexen (iMIC)CuX (X = Cl, Br oder I) (1.87–1.90 Å) [23–24,33] . Die C2−Au1 1.980(6) und C7−Au2 1.983(6) Å Bindungslängen von 8 ‐Ph zeigen Übereinstimmung mit bekannten (iMIC)AuCl‐Komplexen (1.98–2.01 Å) [26]…”

New Cu (I) complexes as catalyst for “click” reaction: An experimental and computational study

“…[23][24][25][26] The coppercatalysed alkyne-azide cycloaddition (CuAAC) reaction represents the flagship transformation of "Click Chemistry" that has considerable applications in organic synthesis, coordination chemistry and material science. [27] With over 2,000 documented reports in about a decade, the CuAAC reaction is notable and undoubtedly has been a breakthrough in organic synthesis and Cu (I) catalysis. [28] In terms of economic viability and sustainability, copper is economical and more abundant in comparison with other metals.…”