Balancing Bulkiness in Gold(I) Phosphino‐triazole Catalysis

Abstract

The syntheses of a series of 1‐phenyl‐5‐phosphino 1,2,3‐triazoles are disclosed, within which, the phosphorus atom (at the 5‐position of a triazole) is appended by one, two or three triazole motifs, and the valency of the phosphorus(III) atom is completed by two, one or zero ancillary (phenyl or cyclohexyl) groups respectively. This series of phosphines was compared with tricyclohexylphosphine and triphenylphosphine to study the effect of increasing the number of triazoles appended to the central phosphorus atom from zero to three triazoles. Gold(I) chloride complexes of the synthesised ligands were prepared and analysed by techniques including single‐crystal X‐ray diffraction structure determination. Gold(I) complexes were also prepared from 1‐(2,6‐dimethoxy)‐phenyl‐5‐dicyclohexyl‐phosphino 1,2,3‐triazole and 1‐(2,6‐dimethoxy)‐phenyl‐5‐diphenyl‐phosphino 1,2,3‐triazole ligands. The crystal structures thus obtained were examined using the SambVca (2.0) web tool and percentage buried volumes determined. The effectiveness of these gold(I) chloride complexes to serve as precatalysts for alkyne hydration were assessed. Furthermore, the regioselectivity of hydration of but‐1‐yne‐1,4‐diyldibenzene was probed.

Confinement‐Induced Selectivities in Gold(I) Catalysis—The Benefit of Using Bulky Tri‐(ortho‐biaryl)phosphine Ligands

“…We completed our studies by considering the possibility to employ the confined tri‐( ortho ‐biaryl)phosphine gold(I) complexes synthesized to induce regioselectivity in the nucleophilic intermolecular functionalization of alkynes. The prototypical hydration reaction of phenylpropyne 36 was used for this purpose [6b,g, 13, 43] . As seen in Scheme 10, the use of the classical ligands Ph 3 P, JohnPhos, XPhos and IPr along with bis‐( ortho ‐biphenyl)phosphine ligand L 8 delivered a mixture of ketones 38 and 39 in high yields (78–99 %), but with very low selectivity (1 : 1.4 on average).…”

“…Interestingly, the simplest representative of gold complex 5 (R=H, X=Cl) has been mentioned in a report by Hammond and Xu, but was shown to be poorly reactive in the hydroamination reaction they studied [10c] . Structurally related systems involving a tri‐kitphos [12] or tri ‐( N ‐phenyltriazolyl) phosphine [13] were also reported, but they demonstrated no significant catalytic activity and no specific selectivity. In this manuscript we report the synthesis of a series of tri‐( ortho ‐biaryl)phosphine gold(I) complexes 5 , their structural analysis and selected applications in catalysis.…”

Optimizing Catalyst and Reaction Conditions in Gold(I) Catalysis–Ligand Development

“…Zhao et al. have systematically assessed a series of 1-phenyl-5-phosphino-1,2,3-triazoles in gold catalysis; these included species with various combinations of triazoles, phenyl groups, and cyclohexyl groups at the phosphorus ( P-20 – P-25 ). The steric bulk of each ligand was measured using % V bur analysis and topographical steric maps, and the ligands were tested in the hydration reactions of terminal (1-decyne) and internal (1,4-diphenylbut-1-yne) alkynes (Scheme ).…”

Enantiomer stability of atropisomeric 1,5-disubstituted 1,2,3-triazoles

“…Thermal, catalyst-free CuAAC, copper-catalysed RuAAC, ruthenium-catalysed NiAAC, nickel-catalysed MeMgBr, Grignard-mediated Et 2 Zn, alkyl zinc-mediated Authors of this report have previously investigated and surveyed 1,2,3-triazoles as scaffolds for sensor assembly, [71][72][73][74] as ligand platforms, 75,76 in asymmetric synthesis [77][78][79] and as linkers, 80,81 and in this report axial chirality of atropisomeric 1,5-substituted 1,2,3-triazoles is probed.…”