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

Abstract

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.

Theoretical insights into ω-alkynylfuran cycloisomerisation catalyzed by Au/CeO2(111): the role of the CeO2(111) support

“…Herein, u-alkynylfuran cycloisomerisation catalyzed by CeO 2 -supported gold nanoparticles (Au 3 , Au 4 , Au 10 , Au 11 ) is explored with the help of density functional theory (DFT), as an expansion of our prior research. [37][38][39] Gold nanoparticles (Au 3 , Au 4 , Au 10 , Au 11 ) were employed for consistence with experimental results reported by Oliver-Meseguer et al and others. [40][41][42] In these studies, it was found that small gold clusters (only 3 to 10 atoms in size) can be formed during the catalytic processes, which can catalyze the ualkynylfuran cycloisomerisation reaction.…”

“…4-7, the rate-limiting step of the 5-exo FCT reaction route in the gas phase is the nucleophilic addition of the Cb atom to the C1 site of the furan ring to form the spiro-intermediate IM2, which has an energy barrier of 13.66 kcal mol À1 , while the formation of IM4 is the rate-determining step in acetonitrile. However, for the DDA pathway, the formation of the b-alkenylated furan and the 6-endo FCT pathway, the energy barriers of the rate-limiting steps are 46 On the basis of our previous reports [37][38][39] and the above discussions, the 5-exo Friedel-Cras-type mechanism (FCT) is the most feasible pathway for u-alkynylfuran cycloisomerisation. Accordingly, the 5-exo FCT mechanism of u-alkynylfuran cycloisomerisation on the various reaction sites of Au 10 / CeO 2 (111) and Au 11 /CeO 2 (111) were investigated.…”

“…The 5-exo Friedel-Cras-type mechanism (FCT) is the most feasible pathway of u-alkynylfuran cycloisomerisation to produce the targeted phenol derivative product, catalyzed by subnanometer gold clusters and planar gold clusters, based on our previous reports. [37][38][39] In order to illustrate the catalytic role of the supporting material, stoichiometric CeO 2 and partially reduced CeO 2 with one vacancy are also considered here. In addition, the possible catalytic sites of Au n /CeO 2 (111), including the atop, edge and interface sites, are investigated, aiming to illustrate the catalytic activity of the catalytic sites and interfacial effects.…”

A DFT Insight into Hashmi Phenol Synthesis Catalyzed by M6@Au32 (M=Ag, Cu, Pd, Pt, Ru, Rh) Core–Shell Nanoclusters

“…We also investigated the full reaction mechanism of ω‐alkynylfuran cycloisomerization using Au 38 as the catalyst . In addition, the planar gold clusters were chosen as models, which are used for catalyzing the ω‐alkynylfuran cycloisomerization . However, to the best of our knowledge, a theoretical understanding of the ω‐alkynylfuran cycloisomerization mechanism on the bimetallic core–shell nanoclusters is still lacking.…”

“…[47] In addition, the planar gold clusters were chosen as models, which are used for catalyzing the w-alkynylfuran cycloisomerization. [48] However,t o the besto fo ur knowledge,atheoreticalu nderstanding of the w-alkynylfuran cycloisomerization mechanism on the bimetallic core-shell nanoclusters is still lacking.T oa chieve this goal and extend the previous work, we herein present DFT calculations to predict the catalytic activities of the M 6 @Au 32 core-shell nanoclusterst oward the w-alkynylfuran cycloisomerization. The Au 38 nanocluster wasc hosen as the catalyst model and was regarded as the template used ford esigning the M 6 @Au 32 coreshell nanoclusters by substitution of the core Au atoms.…”