Mihai Raducan’s research while affiliated with Institute of Chemical Research of Catalonia and other places

... The group of Echavarren reported an alternative type of gold(I) carbenoid 491bearing chloride as leaving group, which can act as methylene carbene equivalent. These carbenoids, upon activation with TMSOTf or AgOTf, display the typical reactivity patterns of metal carbenes: cyclopropanation of alkenes, dimerization, and Buchner reaction (Scheme 111A).637 ...

Reference:

Gold-Catalyzed Synthesis of Small Rings

... This allowed for an appropriate choice of DFT functional to compare xTB against in the second data set, [B], which consists of a representative set of stoichiometric gold reactions (shown in Figure 2), which generally include more realisticallysized systems. The geometries in data set [B] are optimized with PBEh-3c and xTB and include 1) the intramolecular oxidative addition of a naphthyl iodide moiety; [21] 2) a Friedel-Crafts reaction with Au(I) & Au(III); [22] 3) cyclopropanation involving a Au(I) carbene; [23] 4) a 1,6-enyne cycloisomerization with Au(I) [22] and 5) the gold-mediated Cope rearrangement of a 1,5-diene. [24] We probe the similarity of the xTB and PBEh-3c structures by evaluating their energies at the domain-based pair natural orbital coupled cluster method, DLPNO-CCSD(T), [25] to provide a more accurate picture. ...

Reference:

Efficient Computation of Geometries for Gold Complexes

... Cyclopropanation can alternatively occur via at hreecentered transition state TS-I,i na nalogy to the Simmons-Smith reaction, [31] leading to [LAuOTf] (14)a nd cyclopropane 4b (Figure 3). This pathway is energetically accessible and can be considered competent for the formation of cyclopropanes.A lternative mechanisms involving reductive elimination from metallacyclobutane [32] structures were also considered but found to be unlikely (Supporting Information, Figure S33). No path for the formation of ethylene from two carbenoids 12 could be located. ...

Reference:

Gold(I) Carbenoids: On-Demand Access to Gold(I) Carbenes in Solution

... In a later report, 1,3-dicarbonyl compounds 39 were found to react selectively as carbon nucleophiles, delivering cyclopentenes 40 in moderate to good yields and with low to moderate diastereoselectivities (Scheme 15). 32 The intermolecular cyclopropanation with cyclic alkenes 41 yielded cyclopropanes 42 (Scheme 16). Adduct 42a was obtained with a low 56:44 d.r., while benzene-fused alkenes delivered good to excellent diastereoselectivities (products 42bd). ...

Reference:

Assembling Complex Structures through Cascade and Cycloaddition Processes via Non-Acceptor Gold or Rhodium Carbenes

... Crystallography: Crystals suitable for X-ray studies were obtained by vapor diffusion of diethyl ether (7) or n-hexane (2 and 6) over a solution of the corresponding compound in dichloromethane. Crystals were mounted on a MiTeGen Crystal micromount and transferred to the cold gas stream of a Bruker D8 VENTURE diffractometer. ...

Reference:

Ferrocenyl Dinuclear Gold(I) Complexes. Study of their Structural Features and the Influence of Bridging and Phosphane Ligands in a Catalytic Cyclization Reaction

... 385 O-Tethered 1,6-enynes with an enol ether as the alkene component delivered similarly complex cage structures. 386 The intermolecular version of these reactions was developed trapping with external alkenes two different cyclopropyl gold carbene intermediates (116 and 117) generated from 1,6enynes (Scheme 34). 387,388 Cyclopropyl gold carbene 116 can convert to intermediate 117 in a stepwise or concerted manner, namely via a 1,2-shift of the carbene C atom of 116 with concomitant cleavage of the cyclopropane distal C−C bond and double bond formation. ...

Reference:

Gold-Catalyzed Synthesis of Small Rings

... As an alternative to conventional Au I NHCs, hydrogen-bond-supported heterocyclic carbenes (HBHCs) 44 are suitable ligands because they are easily achieved by a mere nucleophilic addition of primary amines to isocyanides, which shows a great advantage over the complicated preparation of NHCs obtained by transmetalation from Ag. In a comparative study, 45 it was observed that Nacyclic carbenes (NACs) 46 were also valid for the skeletal rearrangement of 1,6-enynes, similar to HBHCs, showing the advantage of an easy modulation of their steric and electronic characteristics, which has given rise to an intense search of Au I catalysts that can be obtained by employing these preparation methods. 47,48 Chart 1 shows the types of Au I carbene complexes. ...

Reference:

Microporous Polymeric Networks Containing a Long-Term Stable Au I Catalyst for Enyne Cyclization

... Another important contribution in this area is the work of Echavarren in comprehensive studies of the gold-catalyzed intermolecular addition of carbon nucleophiles to 1,5-and 1,6-enynes. 111 From this report, it became clear that the reaction pathway could be directed by the auxiliary ligand, leading either to cyclopropane or carbenesite selectivity. The presence of NHC ligands, such as IPr, leads to carbene-site selectivity in most cases (Scheme 17). ...

Reference:

The influential : 25 years after its discovery

... Thus, alkoxycyclization products 7a−v were obtained in good yields and good to excellent enantioselectivities from 1,6-enynes 6a−q and alcohols. As expected, 26,52,53 diastereomeric products 7s and 7t were obtained from (E)and (Z)-configured starting materials, respectively. The reaction was also extended to electron-rich C-nucleophiles such as indole and 1,3,5-trimethoxybenzene to provide enantiopure compounds 7w and 7x. ...

Reference:

Practical Synthesis of Chiral Ferrocenenylphosphino-Gold(I) Catalysts and NEST Analysis of the Enantioinduction

... Matsunaga subsequently demonstrated the application of chiral disulfonate anions in enantioselective pyridyl-directed arene C-H functionalizations catalysed by pentamethylcyclopentadienyl (Cp*) rhodium(III) complexes 18 . Despite the highly promising nature of the chiral counteranion approach in transition-metal chemistry, its successful application in asymmetric catalysis has thus far proven limited, a fact that may be attributable to the strong coordinating abilities and/or basicities of the chiral anions [19][20][21] . Furthermore, although ion pairing has been often invoked to account for the enantioselectivity induced by chiral anions, the described properties of the anions give rise to mechanistic alternatives such as the chiral anion acting as a ligand, hydrogen-bond acceptor or Brønsted base [22][23][24] . ...

Reference:

Enantioselective Transition-Metal Catalysis via an Anion-Binding Approach