Porous aromatic frameworks (PAFs) as efficient supports for N-heterocyclic carbene catalysts

Rangel-Rangel, Elizabeth; Verde‐Sesto, Ester; Rasero‐Almansa, Antonia M.; Iglesias, Marta; Sánchez, Félix

doi:10.1039/c6cy00597g

Cited by 28 publications

(27 citation statements)

References 128 publications

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“…More 3D porous aromatic frameworks (PAFs) were reported in the same year, but this time for catalysis applications. Three different PAFs were synthesized, [136] based on the same chemical reactions but with a different central unit: a sp 3 carbon atom (PAFc), an adamantine (PAFad), or a spirobisfluorene (PAFsbf). All them were prepared by the C−C coupling between the corresponding aromatic tetra‐iodide [tetrakis(4‐iodophenyl) methane (TIPM), 1,3,5,7‐tetrakis(4‐iodophenyl)adamantane (TIPA), or 2,2′,7,7′‐tetraiodo‐9,9′‐spirobisfluorene (TISBF)] with 1,4‐benzenediboronic acid (BDBA) under MW heating at 145 °C for 10 or 5 min.…”

Section: D Cofsmentioning

confidence: 99%

Microwave‐Assisted Synthesis of Covalent Organic Frameworks: A Review

et al. 2020

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Covalent organic frameworks (COFs) are relatively recent materials. They have received great attention due to their interesting properties. However, the application of microwaves in their synthesis, despite its advantages such as faster and more reproducible processes, is a minority. Herein, a comprehensive compilation of the research results published in the microwave‐assisted synthesis (MAS) of COFs is presented. This review includes articles of 2D and 3D COFs prepared using microwaves as source of energy. The articles have been classified depending on the functional groups including boronate ester, imines, enamines, azines, and triazines, among others. It compiles the main parameters of synthesis and characteristics of the materials together with some general issues related with COFs and microwaves. Additionally, current and future perspectives of the topic have been discussed.

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Section: D Cofsmentioning

confidence: 99%

Microwave‐Assisted Synthesis of Covalent Organic Frameworks: A Review

et al. 2020

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“…Attempted salt metathesis on (IMes) 2 Ir(H) 2 Cl (186) produced the surprising complex 187 in good yield. In the cationic component of 187, the chloride ligand remained intact and a sodium cation was intercalated between two aryl rings of the NHC ligands (Scheme 71,top or THF ligands were isolated (188 and 189, respectively).…”

Section: The Reactivity In Complexes With Two Nhc Ligandsmentioning

confidence: 99%

“…In the cationic component of 187, the chloride ligand remained intact and a sodium cation was intercalated between two aryl rings of the NHC ligands (Scheme 71,top or THF ligands were isolated (188 and 189, respectively). 99,100 In contrast, a simple change in solvent, from fluorobenzene to THF, gave rise to a double C-H activation / cyclometallation pathway of one of the NHC ligands (190 in (186).…”

Section: The Reactivity In Complexes With Two Nhc Ligandsmentioning

confidence: 99%

“…181 The TH reaction was carried out in a variety of alcohols (iPrOH, cyclohexanol, 1-phenylethanol) and TONs of up to 150 were reached. Finally, the TH reaction was briefly tested with resin-, 182 polyoxometalate-, 183 carbon nanotube-, 184,185 porous polymeric aromatic framework-, 186 and graphene-supported, 187,188 NHC-iridium hybrid materials as catalysts. For further reading on the topic of transfer hydrogenation catalysis, we refer the reader to an excellent recent review by Wang and Astruc.…”

Section: Transfer Hydrogenationmentioning

confidence: 99%

“…The efficiency of porous polymeric aromatic framework supported NHC-Ir catalysts were probed in the Nalkylation reaction of anilines with benzyl alcohol derivatives. 186 Hemilabile interactions were also found to be important in a more classical C-N bond-forming scheme, namely the intramolecular hydroamination reaction.…”

Section: C-n Bond Formationmentioning

confidence: 99%

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Iridium complexes with monodentate N-heterocyclic carbene ligands

Sipos

Dorta

2018

Coordination Chemistry Reviews

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the stoichiometry, both [(IMes)Ir(COE)(N 2)Cl] and [(IMes) 2 Ir(COE)Cl] (198 in Scheme 75) were successfully isolated. 44 Finally, as Scheme 20 in Section 4.4 shows, a series of stable (NHC) 2 Ir(COE)Cl complexes were isolated either by the free carbene or the silver transmetallation method. Scheme 7. The synthesis of half-sandwich NHC-Ir(III) 24. The most commonly used precursor for the synthesis of NHC-Ir(III) complexes is [Cp*IrCl 2 ] 2. In 2000, Herrmann showed that treatment of [Cp*IrCl 2 ] 2 with 1 equivalent of ICy per iridium yielded 24 in an excellent 90% yield (Scheme 7). 45 Termaten et al. employed the same procedure for the synthesis of (IiPr Me)Ir(Cp*)Cl 2 (26a in Scheme 8). 15 An alternative synthetic route to access free NHCs was described in 1993 by Kuhn and Kratz, who prepared free carbenes via the reduction of thiones 25 by metallic potassium in THF (Scheme 8). 46 Using this method, Yamaguchi and coworkers prepared 26a-c by cannulating the solution of the in situ generated NHCs to a solution of [Cp*IrCl 2 ] 2 in THF (Scheme 8). 47 Scheme 8. Synthesis of NHC-Ir(III) from free carbenes. 4.2. Alkoxy metal precursors and base-assisted one-pot methods It was Köcher and Herrmann who first developed a one pot procedure in which [Ir(COD)(µ-OEt)] 2 was prepared in situ by reacting [Ir(COD)Cl] 2 with four equivalents of NaOEt. Subsequently, four equivalents of 1,3-bis(diphenylmethyl)imidazolium bromide were added and the air and moisture stable 27 was isolated two days later (Scheme 9). 48 Interestingly, despite the fact that a large excess of the NHC salt was employed, formation of a cationic biscarbene complex was not observed. Scheme 9. NHC-Ir complex synthesis from an in situ generated metal-alkoxide. The procedure starting with the alkoxy metal precursor gave bis-NHC substituted complexes (28) when sterically less demanding NHC salts were applied (Scheme 10). Notably, even a 2.2:1 ratio of NHC:Ir was sufficient to isolate 28a-c in good yields (67-86%). Iridium and rhodium bis-NHC complexes with chelating N-N bridged NHCs were prepared in the same way. 39 Scheme 10. Cationic biscarbene complexes. Recently, Savka and Plenio described a one-step synthesis to access (NHC)M(COD)Cl (M = Rh, Ir) as well as (NHC)M(CO) 2 Cl complexes by employing a relatively weak base (K 2 CO 3) in acetone under air (Scheme 11). 49 Scheme 11. One pot synthesis of (NHC)Ir(COD)Cl and (NHC)Ir(CO) 2 Cl complexes. 4.3. The silver transmetallation method Scheme 12. The silver transmetallation method. The silver transmetallation method for the synthesis of NHC-iridium complexes was first published by Crabtree and coworkers. 50 The NHC-silver adducts (29) were generated in excellent yields by modifying the original procedure of Wang and Lin. 51 Subsequent treatment of [Ir(COD)Cl] 2 at room temperature gave 30a and 30b in 81 and 68% yield, respectively (Scheme 12). X-ray analysis of the yellow crystals of 30a revealed square planar geometry around the iridium center. Complexes 30 smoothly reacted with CO to form bis-carbonyl compound...

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C‐N Bond Formation Catalyzed by Ruthenium Nanoparticles Supported on N‐Doped Carbon via Acceptorless Dehydrogenation to Secondary Amines, Imines, Benzimidazoles and Quinoxalines

Guo

Zhang

et al. 2018

ChemCatChem

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Ruthenium nanoparticles (NPs) supported on N‐doped carbon (Ru/N−C) were prepared by the pyrolysis of cis‐Ru(phen)2Cl2 loaded onto carbon powder (VULCAN XC72R) at 800 °C. Ru/N−C NPs (0.2 mol% Ru) selectively catalyzed either acceptorless dehydrogenation coupling (ADC) or auto‐transfer‐hydrogen (ATH) reactions of amines with alcohols to imines and secondary amines. Such selectivity could be controlled by the choice of alkali metal ion associated with the base. Under similar catalytic conditions, the ADC cross‐coupling of diamines with primary alcohols or diols afforded the corresponding benzimidazoles and quinoxalines in good to excellent yields. This catalytic system displayed good activity, recyclability, and wide applicability to a diverse range of substrates.

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Porous aromatic frameworks (PAFs) as efficient supports for N-heterocyclic carbene catalysts

Abstract: Polymeric aromatic frameworks (PAFs), easily obtained from organic platforms, as excellent supports to yield robust well-defined organometallic heterogenized catalysts.

Cited by 28 publications

References 128 publications

Microwave‐Assisted Synthesis of Covalent Organic Frameworks: A Review

Microwave‐Assisted Synthesis of Covalent Organic Frameworks: A Review

Iridium complexes with monodentate N-heterocyclic carbene ligands

C‐N Bond Formation Catalyzed by Ruthenium Nanoparticles Supported on N‐Doped Carbon via Acceptorless Dehydrogenation to Secondary Amines, Imines, Benzimidazoles and Quinoxalines

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