Chiral Gold(III) Complexes: Synthesis, Structure, and Potential Applications

Abstract

Since the beginning of the 2000's, homogeneous gold catalysis has emerged as a powerful tool to promote the cyclization of unsaturated substrates with excellent regioselectivity allowing the synthesis of elaborated organic scaffolds. An important goal to achieve in gold catalysis is the possibility to induce enantioselective transformations by the assistance of chiral complexes. Unfortunately, the linear geometry of coordination for gold usually encountered in complexes at the + 1 oxidation states renders this goal very challenging. In consequence, the interest toward the synthesis of chiral gold(III) complexes is steadily growing. Indeed, the square planar geometry of the gold(III) cation appears more suitable to promote chiral induction. Beside catalysis, gold(III) complexes have also shown promising potential in the field of pharmacology. Herein, syntheses and applications of well-defined gold(III) complexes reported over the last fifteen years are summarized.

Enantioselective C−H Functionalization Reactions under Gold Catalysis

“…However, the difficulties associated with the synthesis of stable yet catalytically active and efficient chiral gold(III) complexes hinders this approach. [100][101][102][103][104][105][106] Therefore, number of other strategies has been introduced to induce enantioselectivity in gold-catalyzed transformations. [107][108][109][110][111][112] As far as CÀ H functionalization is concerned, following approaches have been utilized thus far: 1) use of chiral bulky ligands to create an effective chiral pocket; 2) use of a bifunctional ligand Chemistry-A European Journal capable of establishing secondary interaction with substrates; 3) use of chiral counter-anions; 4) use of chiral organo-catalyst along with achiral gold complex.…”

“… [98,99] In this regard, gold(III) complexes are more appealing as they form square planar structures bringing the substrate more closer to the chiral ligand thus allowing a better stereo‐control. However, the difficulties associated with the synthesis of stable yet catalytically active and efficient chiral gold(III) complexes hinders this approach [100–106] . Therefore, number of other strategies has been introduced to induce enantioselectivity in gold‐catalyzed transformations [107–112] .…”

Rh2(ii)-catalyzed enantioselective intramolecular Büchner reaction and aromatic substitution of donor–donor carbenes

“… 13 Despite that these newly developed carbene precursors provide several useful means in the transformation of donor type metal-carbenes, the commonly used gold catalyst usually suffered inefficient chiral induction due to the linear geometry. 14 As a reliable and safe donor-type metal-carbene source, enynones have received much attention due to its versatile activities. 15 In our previous work, we realized the asymmetric intramolecular C–H insertion and cyclopropanation with enynones as carbene precursors.…”

Chiral gold(iii) complexes: speciation, in vitro, and in vivo anticancer profile

“…The synthesis of chiral Au(III) complexes is an exciting area of research with significant contributions to asymmetric catalysis and material science. [7][8][9] Applications of chiral Au(III) complexes as anticancer agents is underexplored but possess tremendous potential. 10 Reports using chiral diamine chelates or isothiourea ligand coordinated to AuCl 3 show minimal to no cytotoxicity.…”

“…17 The novel cationic organometallic Au(III) chlorido complexes [aryl pyridine-Au(III)Cl(R-DuPhos)] (1-7; Fig. 1) were synthesized under mild conditions by reacting 2-benzoylpyridine gold(III) dichloride (1, 5), 2-(p-tolyl)pyridine gold(III) dichloride (2, 6), 2phenylpyridine gold(III) dichloride (3,7), or 2-benzylpyridine gold(III) dichloride (4) with 1,2-bis[(2R,5R)-2,5-dimethyl phospholano]benzene (Me-DuPhos) or 1,2-bis[(2R,5R)-2,5 diisopropylphospholano]benzene (iPr-Duphos) ligands in dichloromethane at room temperature for 15 minutes. Cyclometallation of conjugated pyridines with transition metals has often been a subject of interest in organic electronics due to the possibility of making highly luminescent materials, yet their use in bioinorganic chemistry is rapidly growing.…”