Gold Vinylidene Complexes: Intermolecular C(sp<sup>3</sup>)H Insertions and Cyclopropanations Pathways

Hashmi, A. Stephen K.; Wieteck, Marcel; Braun, Ingo; Rudolph, Matthias; Röminger, Frank

doi:10.1002/anie.201204015

Cited by 176 publications

(57 citation statements)

References 49 publications

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“…In the case of 6 a, the structural resemblance to a classical Wheland-type complex is of additional interest due to reports of similar species being intermediates in gold-catalysed ring-closing chemistry and electrophilic aromatic substitution. [28] Structurally, the AuÀAu separation in 6 a is very similar to that found in hydride-bridged 3 a (2.807(2) vs 2.7571(3) ) and much shorter than that found in chloride-bridged precursor 5 a Very similar chemistry can also be effected using the even more bulky 7-Dipp ligand. Thus, a targeted synthesis of [{(7-Dipp)Au} 2 (m-Cl)][BAr f 4 ] (5 b) through the addition of 0.5 equivalents of Na[BAr f 4 ] to (7-Dipp)AuCl at À5 8C produces the desired chloride-bridged product in 58 % yield (Figure 9).…”

Section: Reactivity Of Chloride-containing Systemsmentioning

confidence: 57%

Expanded‐Ring N‐Heterocyclic Carbenes for the Stabilization of Highly Electrophilic Gold(I) Cations

Phillips

Dodson

Tirfoin

et al. 2014

Chemistry A European J

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Strategies for the synthesis of highly electrophilic Au(I) complexes from either hydride- or chloride-containing precursors have been investigated by employing sterically encumbered Dipp-substituted expanded-ring NHCs (Dipp=2,6-iPr2 C6 H3 ). Thus, complexes of the type (NHC)AuH have been synthesised (for NHC=6-Dipp or 7-Dipp) and shown to feature significantly more electron-rich hydrides than those based on ancillary imidazolylidene donors. This finding is consistent with the stronger σ-donor character of these NHCs, and allows for protonation of the hydride ligand. Such chemistry leads to the loss of dihydrogen and to the trapping of the [(NHC)Au](+) fragment within a dinuclear gold cation containing a bridging hydride. Activation of the hydride ligand in (NHC)AuH by B(C6 F5 )3 , by contrast, generates a species (at low temperatures) featuring a [HB(C6 F5 )3 ](-) fragment with spectroscopic signatures similar to the "free" borate anion. Subsequent rearrangement involves BC bond cleavage and aryl transfer to the carbophilic metal centre. Under halide abstraction conditions utilizing Na[BAr(f) 4 ] (Ar(f) =C6 H3 (CF3 )2 -3,5), systems of the type [(NHC)AuCl] (NHC=6-Dipp or 7-Dipp) generate dinuclear complexes [{(NHC)Au}2 (μ-Cl)](+) that are still electrophilic enough at gold to induce aryl abstraction from the [BAr(f) 4 ](-) counterion.

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Section: Reactivity Of Chloride-containing Systemsmentioning

confidence: 57%

Expanded‐Ring N‐Heterocyclic Carbenes for the Stabilization of Highly Electrophilic Gold(I) Cations

Phillips

Dodson

Tirfoin

et al. 2014

Chemistry A European J

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“…The gold-vinylidene carbenoid complexes are highly reactive intermediates-they are the key intermediate for many goldcatalyzed organic reactions. [51][52][53][54][55][56][57] The formation of Au-vinylidene carbenoid intermediate IM9 is endothermic by about 10.06 (7.98) kcal mol À1 with an energy barrier of 44.95 (41.12) in the gas phase (acetonitrile). Obviously, the formation of the Auvinylidene carbenoid intermediate IM9 is unfavorable thermodynamically and kinetically, which agrees with the experimental ndings.…”

Section: Pathways For the Formation Of Phenolmentioning

confidence: 99%

DFT insights into the cycloisomerization of ω-alkynylfuran catalyzed by planar gold clusters: mechanism and selectivity, as compared to Au(i)-catalysis

et al. 2016

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A detailed reaction mechanism of the triatomic gold cluster-catalyzed cycloisomerization of u-alkynylfuran was systemically investigated via density functional theory at the TPSSh/def2-TZVP level. The computational results indicated that the 5-exo Friedel-Crafts-type mechanism is the most favorable mechanism to form the phenol derivatives. The strong interaction between the gold and vinyl fragments in the Friedel-Crafts adduct is essential for the priority of the 5-exo Friedel-Crafts-type mechanism. Then, the 5-exo Friedel-Crafts-type mechanism on the various planar gold clusters (Au 4-10 ) was studied to clarify the size-effects of the planar gold clusters catalyzed u-alkynylfuran cycloisomerization. The appropriate interactions between the alkyne group in the substrate and gold clusters play a key role for the 5-exo cyclization step. The energy barriers of the ring-closure of the dienone carbene-gold intermediate step show an interesting "odd-even" behavior respective to the number of gold atoms. The Au 3 and Au 4 clusters are the most active catalysts for the u-alkynylfuran cycloisomerization to the phenol derivative. We also found that the active catalyst of the u-alkynylfuran cycloisomerization catalyzed by the gold(I) complexes should be the gold(0) complexes of the in situ generation. The catalytic activity of the gold(0) complex is comparable with that of the planar gold clusters. These findings may guide the rational design of highly active gold catalysts for the u-alkynylfuran cycloisomerization to phenol derivatives. † Electronic supplementary information (ESI) available: Fig. S1-S15, Tables S1-S9, details of the energy decomposition analysis, and the Cartesian coordinates, single point electronic energies (in the gas phase and acetonitrile), zero-point, and free energy correction for all of the stationary points and imaginary frequencies of transition structures. See Scheme 2 Different transition metal complex-catalyzed-u-alkynylfurans cycloisomerizations.Scheme 3 Proposed mechanism for the gold-catalyzed phenol synthesis.

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“…Inspired by their proposed novel reaction mode involving , -type dual activation of diynes substrates [50], Hashmi and coworkers developed an alternative approach for gold vinylidene intermediate formation by using a leaving group replacing the -activated alkyne. They demonstrated that the formation of gold vinylidene intermediates 103 is also possible by the cyclization of gold acetylides alone and therefore not strictly dependent on a dual activation mode.…”

Section: Synthesis Of O-heterocycles and N-heterocyclesmentioning

confidence: 99%

Au‐ and Pt‐Catalyzed CH Activation/Functionalizations for the Synthesis of Heterocycles

Xiao¹,

Zhang²

2016

Transition Metal‐Catalyzed Heterocycle Synthesis via CH Activation

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Gold Vinylidene Complexes: Intermolecular C(sp³)H Insertions and Cyclopropanations Pathways

Cited by 176 publications

References 49 publications

Expanded‐Ring N‐Heterocyclic Carbenes for the Stabilization of Highly Electrophilic Gold(I) Cations

Expanded‐Ring N‐Heterocyclic Carbenes for the Stabilization of Highly Electrophilic Gold(I) Cations

DFT insights into the cycloisomerization of ω-alkynylfuran catalyzed by planar gold clusters: mechanism and selectivity, as compared to Au(i)-catalysis

Au‐ and Pt‐Catalyzed CH Activation/Functionalizations for the Synthesis of Heterocycles

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Gold Vinylidene Complexes: Intermolecular C(sp3)H Insertions and Cyclopropanations Pathways

Cited by 176 publications

References 49 publications

Expanded‐Ring N‐Heterocyclic Carbenes for the Stabilization of Highly Electrophilic Gold(I) Cations

Expanded‐Ring N‐Heterocyclic Carbenes for the Stabilization of Highly Electrophilic Gold(I) Cations

DFT insights into the cycloisomerization of ω-alkynylfuran catalyzed by planar gold clusters: mechanism and selectivity, as compared to Au(i)-catalysis

Au‐ and Pt‐Catalyzed CH Activation/Functionalizations for the Synthesis of Heterocycles

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Gold Vinylidene Complexes: Intermolecular C(sp³)H Insertions and Cyclopropanations Pathways