Expanded‐Ring <i>N</i>‐Heterocyclic Carbenes Efficiently Stabilize Gold(I) Cations, Leading to High Activity in π‐Acid‐Catalyzed Cyclizations

Morozov, Oleg S.; Lunchev, Andrey V.; Буш, А. А.; Tukov, Aleksandr A.; Asachenko, Andrey F.; Khrustalev, Victor N.; Zalesskiy, Sergey S.; Ananikov, Valentine P.; Nechaev, Mikhail S.

doi:10.1002/chem.201303760

Cited by 61 publications

(28 citation statements)

References 42 publications

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“…Next, the nature of the catalyst was studied. As we have previously shown, the nature of counteranion plays a significant role in catalysis by gold–carbene complexes. This was also observed for the reaction of phenylhydrazine with the CF 3 ‐ynone.…”

Section: Resultsmentioning

confidence: 66%

“…In a continuation of our investigation into (THD‐Dipp)AuOTf chemistry,[9f], we envisioned that (THD‐Dipp)AuOTf could be used to carry out the regioselective transformation of CF 3 ‐ynones into CF 3 ‐pyrazoles through reaction with hydrazines.…”

Section: Introductionmentioning

confidence: 79%

“…It is well known that gold(I) species are efficient catalysts of inter‐ and intramolecular hydroamination reactions of alkynes . We have previously shown that a seven‐membered‐ring carbine bearing bulky Dipp (2,6‐diisopropylphenyl) groups can be used in combination with weakly coordinating anions such as triflate to give extremely active catalytic systems. These can be used to catalyse the intramolecular hydroamination of 2‐ethynylanilines to give indoles, and the intermolecular hydrohydrazination of alkynes to give hydrazones, under unprecedentedly mild conditions.…”

Section: Introductionmentioning

confidence: 99%

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Mild and Regioselective Synthesis of 3‐CF₃‐Pyrazoles by the AgOTf‐Catalysed Reaction of CF₃‐Ynones with Hydrazines

et al. 2018

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Gold‐ and silver‐catalysed reactions of trifluoromethylated ynones with aryl (alkyl) hydrazines were investigated. The use of (THD‐Dipp)AuOTf and AgOTf resulted in quick heterocyclization reactions to selectively give 3‐CF3‐pyrazoles. AgOTf was found to be the catalyst of choice, and various 3‐CF3‐pyrazoles were formed in up to 99 % isolated yield with high regioselectivity. The reaction has a broad scope: 3‐CF3‐pyrazoles with alkyl and aryl substituents as well as different functional groups can be prepared by this approach. The known pyrazole drugs Celebrex® and SC‐560 were efficiently prepared to demonstrate the utility of the method. Mechanistic investigations revealed that the reaction involves the formation of a hemiaminal as a key intermediate.

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Section: Resultsmentioning

confidence: 66%

Section: Introductionmentioning

confidence: 79%

Section: Introductionmentioning

confidence: 99%

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Mild and Regioselective Synthesis of 3‐CF₃‐Pyrazoles by the AgOTf‐Catalysed Reaction of CF₃‐Ynones with Hydrazines

et al. 2018

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“…(2) A strong counteranion effect was observed. As anticipated from our mechanistic postulate, 13 complexes of type [Au(IPr)]X, where X = Cl -, TsOand NTf 2 were at best moderately effective in promoting the reaction. [Au(IPr)]BF 4 proved to be much more effective to activate the triple bond towards nucleophilic attack of the nitrogen group (Table 1, entry 12 vs. 5, 8-11, 13).…”

Section: Scheme 2 Design Plan and Plausible Mechanistic Pathway Of The Goldcatalyzed Hydroamination Reactionmentioning

confidence: 69%

Simple and Mild Synthesis of Indoles via Hydroamination Reaction Catalysed by NHC–Gold Complexes: Looking for Optimized Conditions

Michalska

Grela

2015

Synlett

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All reactions were carried out under argon atmosphere in oven-dried glassware with magnetic stirring. Commercially available chemicals were used without further purification. Solvents were distilled prior to use by Solvent Purification System, Mbraun MB-SPS-800.Analytical thin-layer chromatography (TLC) was performed on silica gel 60 with fluorescent indicator UV254 TLC plates. The spots were visualized with UV light (254 nm) and staining with a solution of p-anisaldehyde, followed by heat. Flash column chromatography was performed using silica gel 60 (particle size 0.040-0.063 mm) typically using a n-hexane/ethyl acetate eluent system. FT-IR spectra were recorded with Thermo Scientific TM Nicolet TM iS TM 50 FT-IR spectrometer. NMR spectra were measured at room temperature on a Agilent Mercury 400 MHz spectrometer. NMR spectra were calibrated to the solvent residual signals of CDCl3. 1 H NMR spectra were recorded at 400 MHz. Data are reported as follows: chemical shift, multiplicity (s: singlet, d: doublet, t: triplet, q: quartet, qui: quintuplet, m: multiplet), coupling constant (J in Hz) and integration. 13 C NMR spectra were recorded at 100 MHz using broadband proton decoupling and chemicals shifts are reported in ppm using residual solvent peaks as reference. Carbon multiplicities were assigned by DEPT techniques.High resolution mass spectra were recorded on a MS (ESI) spectra LCMS-IT TOF Shimadzu.Melting points were measured using open capillary tubes on a MPM-HV2 analyzer. 2.The hydroamination reaction General procedure for the synthesis of gold(I) complexes 1A mixture of silver(I) oxide (1 eq) and corresponding imidazolium or imidazolinium salt (1.6 eq) in dichloromethane (0.05 mol/L) was stirred overnight in dark. The mixture was filtered through Celite and evaporated under reduce pressure. The residue was dissolved in dichloromethane (0.09 mol/L) and (dimethyl sulfide)gold(I) complex (1 eq) was added. The resulting mixture was stirred overnight and filtered through Celite, the solvent was removed in vacuo. The obtained Au(NHC)Cl complex was crystallized form pentane. General procedure for the synthesis of 2-alkynylanilines 2Under argon gas, a mixture of 2-iodoaniline (1 eq), alkyne (1.1-1.3 eq), CuI (3 mol%), PdCl2(PPh3)2 and Et3N ([substrate] = 0.45 mol/L) as solvent was stirred for 2h at 50 . The ℃ reaction mixture was next diluted in water and extracted with CH2Cl2. The organic phase was dried over MgSO4 and the solvent was evaporated under reduce pressure. The crude product

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“…N ‐Methyl‐2‐(phenylethynyl)aniline (9): 24 2‐(Phenylethynyl)aniline ( 7 ) (193 mg, 1.0 mmol) was dissolved in THF (5 mL) under inert atmosphere and cooled to –78 °C. n BuLi solution (10 M in hexanes, 0.11 mL, 1.1 equiv.)…”

Section: Methodsmentioning

confidence: 99%

Modular Access to Tetrasubstituted Imidazolium Salts through Acid‐Catalyzed Addition of Isocyanides to Propargylamines

2015

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Propargylamines, prepared through A3‐coupling of primary amines, aldehydes and terminal alkynes, react with isocyanides in an HCl‐catalyzed process to yield tetrasubstituted imidazolium salts. The key step of the mechanism involves the generation of an amidine intermediate, from the isocyanide insertion into the N–H bond of the propargylamine, which in situ evolves by cyclization upon the alkyne moiety. The scope of the process is analyzed and only shows restrictions for aliphatic amines, whereas it is quite general regarding the aldehyde, alkyne and isocyanide inputs. The protocol allows the preparation of a wide array of adducts, tandem one‐pot processes being also feasible. Mechanistic studies using selected substrates have been used to determine the profile of the reaction and some substitution and functional group limitations. Some post‐synthetic transformations of the imidazolium salts have been performed as well.

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Expanded‐Ring N‐Heterocyclic Carbenes Efficiently Stabilize Gold(I) Cations, Leading to High Activity in π‐Acid‐Catalyzed Cyclizations

Cited by 61 publications

References 42 publications

Mild and Regioselective Synthesis of 3‐CF₃‐Pyrazoles by the AgOTf‐Catalysed Reaction of CF₃‐Ynones with Hydrazines

Mild and Regioselective Synthesis of 3‐CF₃‐Pyrazoles by the AgOTf‐Catalysed Reaction of CF₃‐Ynones with Hydrazines

Simple and Mild Synthesis of Indoles via Hydroamination Reaction Catalysed by NHC–Gold Complexes: Looking for Optimized Conditions

Modular Access to Tetrasubstituted Imidazolium Salts through Acid‐Catalyzed Addition of Isocyanides to Propargylamines

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Expanded‐Ring N‐Heterocyclic Carbenes Efficiently Stabilize Gold(I) Cations, Leading to High Activity in π‐Acid‐Catalyzed Cyclizations

Cited by 61 publications

References 42 publications

Mild and Regioselective Synthesis of 3‐CF3‐Pyrazoles by the AgOTf‐Catalysed Reaction of CF3‐Ynones with Hydrazines

Mild and Regioselective Synthesis of 3‐CF3‐Pyrazoles by the AgOTf‐Catalysed Reaction of CF3‐Ynones with Hydrazines

Simple and Mild Synthesis of Indoles via Hydroamination Reaction Catalysed by NHC–Gold Complexes: Looking for Optimized Conditions

Modular Access to Tetrasubstituted Imidazolium Salts through Acid‐Catalyzed Addition of Isocyanides to Propargylamines

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Mild and Regioselective Synthesis of 3‐CF₃‐Pyrazoles by the AgOTf‐Catalysed Reaction of CF₃‐Ynones with Hydrazines

Mild and Regioselective Synthesis of 3‐CF₃‐Pyrazoles by the AgOTf‐Catalysed Reaction of CF₃‐Ynones with Hydrazines