Chiral-at-Metal Rh(III) Complex-Catalyzed Michael Addition of Pyrazolones with α,β-Unsaturated 2-Acyl Imidazoles

Li, Shiwu; Wan, Qian; Kang, Qiang

doi:10.1021/acs.orglett.8b00040

Cited by 47 publications

(13 citation statements)

References 57 publications

(13 reference statements)

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“…20 For Complex-S, complexation is abnormal owing to the complex function of both the imidazole and cyano group with transition metals. 21,22 Therefore, Complex-S has a different ratio to those reported results.…”

Section: Resultscontrasting

confidence: 72%

A thermal latent imidazole complex containing copper (II) as the curing agent for an epoxy-based glass fiber composite

Yang

Wei

Liu

et al. 2022

Textile Research Journal

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Epoxy-based glass fiber composites are widely used in various fields, such as automotive, marine, and aircraft, owing to their high strength and light weight compared to traditional metal materials. However, the epoxy-based resins or prepregs cannot be stored for a long time at room temperature owing to their high reactivity. In this study, 1-cyanoethyl-2-ethyl-4-methylimidazole (CEMI) is a complex with copper chloride to improve its thermal latency towards epoxy resins, and the epoxy-based glass fiber composite is made by prepreg processing. The composition of the imidazole–copper (II) complex (Complex-S) is characterized by elemental analysis and inductively coupled plasma optical emission spectrometry. Thermal dissociation of Complex-S is conducted by differential scanning calorimetry and Fourier transform infrared spectroscopy. With Complex-S as a latent curing agent, the thermal and mechanical properties of epoxy resins are studied. The epoxy systems show distinctly prolonged shelf life at room temperature. Moreover, the composite with Complex-S has a higher flexure strength and modulus comparable to that with CEMI.

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Section: Resultscontrasting

confidence: 72%

A thermal latent imidazole complex containing copper (II) as the curing agent for an epoxy-based glass fiber composite

Yang

Wei

Liu

et al. 2022

Textile Research Journal

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“…Kang and co‐workers recently described the use of Λ‐ RhO2 in the enantioselective conjugate addition of pyrazolones 43 to 1 (Scheme a) . N ‐Methylimidazole unit was crucial to obtain high yields and enantioselectivities.…”

Section: Metal‐centered Chirality Catalysismentioning

confidence: 97%

“…Kang and co-workers recently described the use of Λ-RhO2 in the enantioselective conjugate addition of pyrazolones 43 to 1 (Scheme 23a). [30] N-Methylimidazole unit was crucial to obtain high yields and enantioselectivities. In fact, when it was replaced by 2-pyridyl moiety (see 46) much lower ee values were attained and in the presence of 1-pyrazole ring the transformation was very reluctant (traces of product 45) (Scheme 23b).…”

Section: Addition Of Soft Nucleophilesmentioning

confidence: 99%

Acyl‐Imidazoles: A Privileged Ester Surrogate for Enantioselective Synthesis

et al. 2019

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Since the first report by Evans in asymmetric Friedel-Crafts reactions, the use of acyl-imidazoles has blossomed as powerful ester/amide surrogates. The imidazole scaffold indeed displays stability and special activation features allowing both better reactivity and selectivity in traditional ester/amide functionalizations: α-(enolate chemistry), β-(conjugate additions), α,β-(cyclo-additions) or γ/δ-(vinylogous). An overview of the contemporary and growing interest in acyl-imidazoles in metal-and organo-catalyzed transformations (bio-hybrid catalytic systems will be fully described in a back-to-back Minireview) will be highlighted. Moreover, post-functionalization expediencies are also going to be discussed in this Minireview. Scheme 1. Synthesis of acyl-imidazoles by Okamoto and co-workers.Scheme 2. Synthesis of α,β-unsaturated acyl-imidazoles. . α-Alkylation of 2-naphthylmethyloxy acyl-imidazoles through PTC catalysis. NPM = 2-naphthylmethyl.Scheme 47. Chemo-and enantioselective oxidative cycloetherification of 2acyl-imidazoles with chiral quaternary ammonium salts. (please, change the chemdraw scheme 47; a new one is given) Scheme 48. Organocatalyzed enantioselective conjugate addition of aryl trifluoroborate to α,β-unsaturated 2-acyl 1-methylimidazole. 2 3 4 5 6 7 8

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“…The role of the carbazole moiety is unclear. However, we and independently the Kang group– found that for related bis‐cyclometalated catalysts the functionalization of the phenyl moiety at this position with an aryl moiety can sometimes have a positive effect on the stereocontrol.…”

Section: Resultsmentioning

confidence: 99%

Kinetic Resolution of Epoxides with CO₂ Catalyzed by a Chiral‐at‐Iridium Complex

et al. 2018

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Chiral‐at‐metal bis‐cyclometalated iridium(III) complexes are introduced as a new class of chiral catalysts for the reaction of epoxides with CO2 to form cyclic carbonates under conditions of kinetic resolution. Reactions are typically performed at room temperature in the presence of 1 mol % of iridium catalyst and 1.5 mol % of tetraethylammonium bromide as the nucleophilic cocatalyst to provide selectivity factors of up to 16.6. A variety of monosubstituted epoxides, including styrene epoxide, epoxides with aliphatic side chains, glycidyl ethers, and a glycidyl ester, are found to be suitable substrates. No polymerization side reaction is observed for any of the investigated substrates.

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Chiral-at-Metal Rh(III) Complex-Catalyzed Michael Addition of Pyrazolones with α,β-Unsaturated 2-Acyl Imidazoles

Cited by 47 publications

References 57 publications

A thermal latent imidazole complex containing copper (II) as the curing agent for an epoxy-based glass fiber composite

A thermal latent imidazole complex containing copper (II) as the curing agent for an epoxy-based glass fiber composite

Acyl‐Imidazoles: A Privileged Ester Surrogate for Enantioselective Synthesis

Kinetic Resolution of Epoxides with CO₂ Catalyzed by a Chiral‐at‐Iridium Complex

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Chiral-at-Metal Rh(III) Complex-Catalyzed Michael Addition of Pyrazolones with α,β-Unsaturated 2-Acyl Imidazoles

Cited by 47 publications

References 57 publications

A thermal latent imidazole complex containing copper (II) as the curing agent for an epoxy-based glass fiber composite

A thermal latent imidazole complex containing copper (II) as the curing agent for an epoxy-based glass fiber composite

Acyl‐Imidazoles: A Privileged Ester Surrogate for Enantioselective Synthesis

Kinetic Resolution of Epoxides with CO2 Catalyzed by a Chiral‐at‐Iridium Complex

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Kinetic Resolution of Epoxides with CO₂ Catalyzed by a Chiral‐at‐Iridium Complex