Chiral [2.2]paracyclophane-based NAC- and NHC-gold(I) complexes

Göker, Verena; Kohl, Simon R.; Röminger, Frank; Meyer-Eppler, Georg; Volbach, Lucia; Schnakenburg, Gregor; Lützen, Arne; Hashmi, A. Stephen K.

doi:10.1016/j.jorganchem.2015.03.010

Cited by 25 publications

(10 citation statements)

References 15 publications

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“…A few years later, Hashmi et al developed an elegant gold-catalyzed furan-yne cyclization leading to isochromane derivatives 163 (Scheme 30) [96]. Although many chiral and acyclic gold(I) complexes 125 have been tested, the corresponding heterocycles of 163 type were obtained with low enantiomeric excess.…”

Section: Chromane and Isochromane Derivativesmentioning

confidence: 99%

“…The respective gold complexes 125 were obtained with good to excellent yields. The synthesis of acyclic NHC gold(I) complexes with C 1 -symmetry.Further studies of the Hashmi group[96] have revealed that the same methodology could be applied for the synthesis of chiral acyclic gold(I) complexes 125 bearing a chiral [2.2]paracyclophane moiety (Scheme 20). The respective racemic amine 120 was separated by chromatography on a preparative chiral column and transformed into isonitrile 123.…”

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confidence: 99%

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Chiral N-heterocyclic Carbene Gold Complexes: Synthesis and Applications in Catalysis

Michalak

Kośnik

2019

Catalysts

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N-Heterocyclic carbenes have found many applications in modern metal catalysis, due to the formation of stable metal complexes, and organocatalysis. Among a myriad of N-heterocyclic carbene metal complexes, gold complexes have gained a lot of attention due to their unique propensity for the activation of carbon-carbon multiple bonds, allowing many useful transformations of alkynes, allenes, and alkenes, inaccessible by other metal complexes. The present review summarizes synthetic efforts towards the preparation of chiral N-heterocyclic gold(I) complexes exhibiting C 2 and C 1 symmetry, as well as their applications in enantioselective catalysis. Finally, the emerging area of rare gold(III) complexes and their preliminary usage in asymmetric catalysis is also presented. Scheme 3. The synthesis of a gold(I) complex from (R)-1-aminotetralin.An elegant approach to C2-symmetric gold(I) complexes was described by Czekelius et al. [72] (Scheme 4), inspired by previous Herrmann's work [73]. The synthetic approach involves chiral amines 24, readily available from the corresponding phenylacetic acid 22 via the Friedel-Crafts reaction of bromobenzene and fractional crystallization of the corresponding tartaric acid amine salt upon reductive amination. The resulting amine 24 was further formylated and subjected to Bischler-Napieralski cyclization to give 3-aryl-substituted dihydroisoquinoline 25. Subsequent reductive coupling afforded the basic diamine skeleton 26 into a single diastereomer, which appeared a perfect platform for structural ligand diversification via Suzuki coupling. The functionalized diamines 26 were then cyclized into imidazolium salts 27 with triethyl orthoformate to give the products with yields in the range of 49-94% (for selected examples, see Scheme 4). The formation of gold(I) complexes 28 was accomplished under rather unusual conditions, by the reaction of gold(I) chloride with a carbene generated by the action of KOtBu. Scheme 4. The synthesis of C2-symmetric gold(I) complexes accessible via a reductive coupling. The application of other chiral building blocks has recently been reported by the Toste group (Scheme 5) [74]. Besides chiral amines, amino alcohols 29 were also utilized in the synthesis of C2-Scheme 3. The synthesis of a gold(I) complex from (R)-1-aminotetralin.An elegant approach to C 2 -symmetric gold(I) complexes was described by Czekelius et al. [72] (Scheme 4), inspired by previous Herrmann's work [73]. The synthetic approach involves chiral amines 24, readily available from the corresponding phenylacetic acid 22 via the Friedel-Crafts reaction of bromobenzene and fractional crystallization of the corresponding tartaric acid amine salt upon reductive amination. The resulting amine 24 was further formylated and subjected to Bischler-Napieralski cyclization to give 3-aryl-substituted dihydroisoquinoline 25. Subsequent reductive coupling afforded the basic diamine skeleton 26 into a single diastereomer, which appeared a perfect platform for structural ligand diversification via Suzuki...

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Section: Chromane and Isochromane Derivativesmentioning

confidence: 99%

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confidence: 99%

Chiral N-heterocyclic Carbene Gold Complexes: Synthesis and Applications in Catalysis

Michalak

Kośnik

2019

Catalysts

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“…Hashmi and co‐workers reported Au(I) complexes, 212 and 213 , of NHC ligands derived from planar chiral [2,2]paracyclophane using isonitriles and amines . These complexes differ by the substituents, isopropyl and cyclododecyl, on the imidazole nitrogen atoms, while the chiral [2,2]paracyclophane substituent is same.…”

Section: Au(i)‐carbene Complexes Of Chiral Nhc Ligandsmentioning

confidence: 99%

Coinage Metal Complexes of Chiral N‐Heterocyclic Carbene Ligands: Syntheses and Applications in Asymmetric Catalysis

et al. 2020

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Chiral N‐heterocyclic carbenes (NHCs) have become ligands of choice due to their remarkable catalytic activity in organic transformation reactions. Combining the chiral NHC ligand family and coinage metals became a productive area of research. The organometallic chemistry of coinage metals with the chiral N‐heterocyclic carbene (NHC) ligands is reviewed, with a special emphasis on the synthesis, characterization and possible applications obtained. Significant sections are devoted to the various recently developed coinage metal‐chiral NHC complexes and a detailed comparison of their activities which aims to rationalize the structure–activity relationships. Various methods of preparations of coinage metal‐chiral NHC complexes along with some typical examples of reactivity and mechanisms are covered. Cu‐chiral NHC complexes involved in conjugated additions, allylic substitutions, boration of alkenes, hydrosilylation of ketones and formation of alkenes are covered, along with some remarkable examples and reactivity of Ag‐chiral NHC complexes. Finally, applications of Au‐chiral NHC complexes in the asymmetric cyclization of ester‐functionalized 1,6‐enynes, 1,6‐enyneamines and substituted propargyloxymethanes are also reviewed.

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“…The sterically less hindered gold(I) complex (a R )‐ Au16 , bearing a pyrrolidin‐1‐yl group, was identified as the best catalyst in the enantioselective acetoxycyclization of 1,6‐enyne 297 , furnishing product 298 in more than 99 % yield with 59 % ee . In 2015, Hashmi and co‐workers developed two classes of chiral [2.2]paracyclophane‐based NAC (N‐acyclic carbene)– and NHC–gold(I) complexes, both of which were prepared by a modular template synthesis by using isonitriles and enantiomerically pure, planar chiral [2.2]paracyclophane amine as the starting materials . They then applied them to enantioselective enyne cyclization.…”

Section: Cycloisomerization or Cyclization Of Enynesmentioning

confidence: 99%

“…Continuing their interest in asymmetric phenol synthesis, in 2015, Hashmi and co‐workers applied their newly developed chiral [2.2]paracyclophane‐based NAC– and NHC–gold(I) complexes to enantioselective furanyne cyclization . Although various gold complexes were tested and a lot of reaction parameters were investigated, the best ee value obtained for the reaction of difuranyne 430 was only 21 % (Scheme ), which seemed unsatisfactory and was inferior to the results acquired with the traditional biaryl diphosphine ligand.…”

Section: Other Miscellaneous Reactionsmentioning

confidence: 99%

Gold‐Catalyzed Enantioselective Annulations

Zhang

2016

Chemistry A European J

218

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Non-oxidative,regioselective,and convergent access to densely functionalized oxazoles is realized in af unctional-group tolerant manner using alkynyl thioethers.S ulfur-terminated alkynes provideaccess to reactivity previously requiring strong donor-substituted alkynes such as ynamides.Sulfur does not act in an analogous donor fashion in this gold-catalyzed reaction, thus leading to complementary regioselective outcomes and addressing the limitations of using ynamides. Compared to other heteroatom-substituted alkynes,alkynyl thioethers are remarkably little explored in intermolecular late-transition-metal catalysis,d espite being readily accessed and robust. [1, 2] Ynamides,i nc ontrast, are privileged sub-strates:i np-acid catalysis their donor nature aids metal-alkyne coordination and affords highly polarized electro-philes,t hus providing the high chemo-and regioselectivity required for the discovery of efficient intermolecular reactions (Scheme 1a). [3,4] As the resulting inclusion of ad onor-nitrogen atom limits the utility of the products,r etaining the reactivity profile of these transformations whilst accessing more flexible and readily elaborated substitution patterns would be desirable.T he value of sulfur-substituted compounds [5] coupled with progress in C À Ca nd C-heteroatom bond formation from CÀSbonds, [6] renders alkynyl thioethers appealing alternatives to ynamides.I ndeed the ketenethio-nium pathway (Scheme 1a)f rom alkynyl thioethers has recently been invoked in proton-catalyzed reactions with nitriles [2g,h] and gold-catalyzed reactions with sulfides. [2i] Ynamides enabled the discovery of formal [3+ +2] dipolar cycloadditions with nucleophilic nitrenoids, [7] thus allowing intermolecular access to a-imino gold carbene-type reactivity for heterocycle synthesis (Scheme 1b). [8, 9] Such reactions, which do not depend on ynamides,a re scarce. [8b,h] As trong donor alkyne substituent proved critical in the formation of oxazoles using N-acyl pyridinium N-aminides,aselectron-rich alkynes such as anisole derivatives did not react (Scheme 1b, inset). [8a,b] Oxazoles are valuable synthetic intermediates [10,11] and structural components in bioactive natural products, [12] agrochemicals, [13] ligands, [14] and functional materials. [15] Despite recent advances,asingle modular and convergent route to trisubstituted oxazoles,which provides the structural and functional-group diversity needed across the 2-, 4-, and 5-positions,r emains unrealized. [16] Following our interest in the use of gold catalysis with sulfides [17] we report here on the reactivity of alkynyl thioethers with nucleophilic nitrenoids to prepare oxazoles. Importantly,t he regioselectivity is not consistent with ac on-trolling ketenethionium species.T he sulfur group plays an alternative role in enabling reactivity,t hus proving complementary to donor-enabled approaches. Ther eaction of the alkynyl thioether 1a and aminide 2a (Table 1) showed that conversion into the oxazole 3 was possible at 125 8 8Ci n1 ,2-dichlorobenzene (1,2-DCB;s ...

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Chiral [2.2]paracyclophane-based NAC- and NHC-gold(I) complexes

Cited by 25 publications

References 15 publications

Chiral N-heterocyclic Carbene Gold Complexes: Synthesis and Applications in Catalysis

Chiral N-heterocyclic Carbene Gold Complexes: Synthesis and Applications in Catalysis

Coinage Metal Complexes of Chiral N‐Heterocyclic Carbene Ligands: Syntheses and Applications in Asymmetric Catalysis

Gold‐Catalyzed Enantioselective Annulations

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