1,2,3-Triazolium-Derived Mesoionic Carbene Ligands Bearing Chiral Sulfur-Based Moieties: Synthesis, Catalytic Properties, and Their Role in Chirality Transfer

Abstract

1,2,3-Triazole-derived mesoionic carbenes (MICs) having a chiral sulfur functional group at the C5 position are easily available through a CuAAC between chiral alkynyl sulfoxides and different azides. The MICs form complexes with several metals (Au, Ag, Ir, Rh, and Ru) that are enantiomerically pure. Moreover, enantiomerically pure MIC sulfinilimines are obtained from the corresponding sulfoxide retaining the chirality. Through this article, the participation of sulfoxide moieties in different catalytic and chirality transfer processes, as well as in discovering mechanistically new processes will be shown. The role of the sulfur chiral moiety in catalytic cycloisomerization and cycloisomerization–dimerization processes using Au–MIC catalysts is dual. The sulfur functional group either stabilizes intermediates in the catalytic cycle, allowing for the reaction to occur or significantly increases the selectivity of the cyclization processes. 1,2,3-Triazole MICs having chiral sulfoxides at C5 are extremely efficient in preparing chiral at the metal complexes by C–H insertion processes. The chiral at the metal half-sandwich complexes, having the enantiopure sulfur chiral group unaltered, experiences different reactions with complete retention of the configuration. Finally, mechanistically new processes, like the desulfinilation of 1,2,3-triazolium salts in Ag–MIC complexes have been uncovered. These still-nascent classes of compounds will offer opportunities for the discovery of novel catalytic applications and to study new mechanistically sound processes.

β-Lactam and penicillin substituted mesoionic metal carbene complexes

“…17 We were interested in determining the suitability as catalysts of the above prepared β-lactam and penicillin substituted MIC-complexes. Based on our previous experience using MIC metal complexes as catalysts 18 we chose the Au( i ) cycloisomerization of enynes and the Pt( ii ) hydrosilylation of alkynes to determine both the catalytic activity of these complexes and the integrity of the labile β-lactam (especially the penicillin bicyclic ring) during the catalytic process. This fact could be tested by determining the influence of the substitution on the four membered ring in the catalytic outcome.…”

Chiral‐at‐Metal BODIPY‐Based Iridium(III) Complexes: Synthesis and Luminescence Properties

“…Three differently substituted 1,2,3‐triazolyl sulfoxides 3 were obtained by reaction of NfN 3 (nonafluorobutanesulfonyl or nonaflyl azide) and the corresponding aniline to generate “in situ” the azide, [ 17 ] and subsequent Cu‐catalyzed azide‐alkyne cycloaddition in mixtures MeOH/H 2 O/Et 2 O as solvent, using CuSO 4 · 5H 2 O/sodium ascorbate as the catalyst. [ 8 ] The yields on compounds 3 were acceptable to good (41–80 %) (Scheme 1).…”

“…During our work in the synthesis of transition metal complexes having 1,2,3-triazolylidene (MIC) ligands with enantiopure sulfoxide and sulfoxiimine moieties, [8] we have reported the role of the chiral mesoionic carbene ligand (MIC) in defining the catalytic reactivity of their Au(I) derivatives, [9] preparing enantiopure chiral-at-metal complexes, [10] and enantiopure complexes having chiral-at-metal and chiral planar metallocene moieties. [11] On the other hand, our work in push-pull systems containing a Cr(0) and W(0) Fischer metal carbene moiety, I, clearly demonstrated that the system geometry is reflected in the deactivation of the fluorescence.…”

Pincer‐Type Mesoionic Carbene Nickel(II) Complexes: Synthesis, Properties, Reactions, and Catalytic Application to the Suzuki–Miyaura Coupling Reaction of Aryl Bromides

“…Mesoionic carbenes (MICs) have recently attracted a lot of attention in the field of transition-metal catalysis for organic transformations [1][2][3][4][5][6][7][8][9] and photophysical materials. [10][11][12][13][14][15][16] In particular, 1,2,3-triazol-5-ylidene (triazolylidene) is the most attractive ligand motif and has been well established because it can be easily synthesized via the [3 + 2] Huisgen reaction between alkynes and azides.…”