Influence of Carbene and Phosphine Ligands on the Catalytic Activity of Gold Complexes in the Hydroamination and Hydrohydrazination of Alkynes

Abstract

Through kinetic measurements, catalytic and stoichiometric experiments, as well as DFT calculations, we compare the catalytic activity of gold complexes supported by a variety of ligands (R3P, NHC, CAAC-5, CAAC-6, BiCAAC) in the hydroamination and hydrohydrazination of alkynes. This study provides a rationale for the superior efficiency of a gold complex bearing a bicyclic (alkyl)(amino)carbene (BiCAAC). We demonstrate that this ligand motif, which is readily available, provides a durable gold catalyst able to compete with sophisticated state-of-the-art phosphine and NHC ligands, which feature secondary interaction capabilities.

Cyclic (Alkyl)(amino)carbene Ligands Enable Cu‐Catalyzed Markovnikov Protoboration and Protosilylation of Terminal Alkynes: A Versatile Portal to Functionalized Alkenes**

“…Taken together these observations clarify the higher a-selectivity obtained with the more donating BiCAAC and CAAC 6 ligands,which also benefit from aflexible steric environment that is more amenable to substrate modularity. [6,26,27] It is noteworthy that these observations contrast with previous reports using NHC ligands in which the a-vs. b-selectivity was rationalized through the respective electronic properties of the ligands (i.e. b-selectivity for SIAd:HOMO = À5.34 eV; aselectivity for SIMes:H OMO = À5.70 eV).…”

Towards the rational design of ylide-substituted phosphines for gold(i)-catalysis: from inactive to ppm-level catalysis

“…A comparison of the ligand structures and the performance of their gold complexes is shown in Figure 7. 5,7,9,26 Aniline (1 eq. ), phenylacetylene (1 eq.…”

Gold(I) complexes bearing ring‐fused benzoxazine‐derived triazolylidenes and their use in C–N bond‐forming processes

“…However, its performance is still behind the [ iPr BiCAACAu] + complex recently reported by Yazdani et al [18] In terms of the hydroamination, even though complex 2b is not as active as the known Michelet L-shaped [NHC-Au] + complex, [8a] it performs similarly than the other catalysts presented in Table 6. Tolentino et al [16b] b Manzano et al [16c] c Mendoza-Espinosa et al [11h] d Yazdani et al [18] e This work. f Flores-Jarillo et al [11k] g Tang et al [8a] Based on previous reports, [19] a plausible general reaction mechanism for the MIC-Au(I)-catalyzed hydroamination and hydrohydrazination processes is depicted in Scheme 3.…”

“…In general, the catalytic hydrohydrazination performances of complex 2b compares well with mesoionic [MIC–Au] + catalysts reported by Manzano et al, [ 16c ] Tolentino et al, [ 16b ] and our group [ 11h,k ] in terms of catalyst loading, conversions, time, and reaction temperatures. However, its performance is still behind the [ iPr BiCAACAu] + complex recently reported by Yazdani et al [ 18 ] In terms of the hydroamination, even though complex 2b is not as active as the known Michelet L‐shaped [NHC–Au] + complex, [ 8a ] it performs similarly than the other catalysts presented in Table 6.…”