When gold meets chiral Brønsted acid catalysts: extending the boundaries of enantioselective gold catalysis

Inamdar, Suleman M.; Ashok, K.; Patil, Nitin T.

doi:10.1039/c4cc04633a

Cited by 105 publications

(40 citation statements)

References 104 publications

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“…This specific mode of activation of multiple bonds enables a plethora of unusual transformations [1][2][3][4][5][6][7][8][9][10][11]. Considering the enantioselective transformations catalyzed by gold compounds [12][13][14][15][16][17][18][19][20][21], the main difficulty arises from the structural features of the respective complexes. Gold(I) complexes exhibit a linear geometry with unrestricted rotation around L-Au as well as Au-substrate bonds (Figure 1) [22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%

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

Michalak

Kośnik

2019

Catalysts

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“…These studies will not be covered, but reviews have been published outlining most of this work [119,120]. Gong et al have demonstrated the coupling of an azlactone, and an alkynol could be achieved by using an achiral phosphine gold methyl complex with an equimolar amount of chiral phosphoric acid (Scheme 30).…”

Section: Scheme 29 Synthesis Of Enantioenriched Bis(indoyl)tetrahydromentioning

confidence: 97%

Enantioselective Gold-Catalyzed Synthesis of Heterocyclic Compounds

Miles

Toste

2015

Topics in Heterocyclic Chemistry

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Asymmetric gold-catalyzed syntheses of a diverse range of heterocycles are described herein. This chapter outlines efforts toward the construction of these molecules via intermolecular, intramolecular, and tandem cyclization strategies. Additionally, asymmetric hydrogenation and epoxidation approaches are detailed. These methodologies generally utilize substrates containing soft, unsaturated carbon-carbon bonds, which can easily interact with the carbophilic gold atom(s). Mostly through the use of bis-or monophosphine ligands, modest to excellent yields and enantioselectivities are obtained for a variety of partially and fully saturated heterocycles. Although steric variation of the phosphine catalyst is the most commonly used strategy for enantioinduction, the use of chiral counteranions has proven useful for more challenging transformations. This chapter includes only examples of syntheses where a chiral gold catalyst is used in the direct formation of the heterocycle; examples of pendant functionalization of an existing heterocycle or chirality transfer from enantioenriched substrate to product are not included.

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“…Treatment of alkynes and a PNO with a gold catalyst and methanesulfonic acid led to α-mesyloxy ketones accompanied by α-(4-hydroxybutoxy) ketones formed via THF incorporation [1228]. The formation of β-alkoxy-α,β-unsaturated ketones from propargylic ethers was often accompanied by a 1,2-shift of the A c c e p t e d M a n u s c r i p t 161 propargylic R group, however this process could be controlled through choice of ligand and through electronic effects [1229]. Formation of an α-oxocarbene complex from an alkyne followed by a β-C-H insertion was a key step in the total synthesis of citrinidins A and B [1230].…”

Section: )mentioning

confidence: 98%

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014

Herndon

2016

Coordination Chemistry Reviews

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When gold meets chiral Brønsted acid catalysts: extending the boundaries of enantioselective gold catalysis

Cited by 105 publications

References 104 publications

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

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

Enantioselective Gold-Catalyzed Synthesis of Heterocyclic Compounds

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014

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