Niobium(<scp>v</scp>) chloride and imidazolium bromides as efficient dual catalyst systems for the cycloaddition of carbon dioxide and propylene oxide

Wilhelm, Michael E.; Anthofer, Michael H.; Reich, Robert M.; D’Elia, Valerio; Basset, Jean‐Marie; Herrmann, Wolfgang A.; Cokoja, Mirza; Kühn, Fritz E.

doi:10.1039/c3cy01057k

Cited by 61 publications

(32 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[41] However,t he reaction catalyzedb yN b(EtO) 5 /NBu 4 Br was found to also produce al inear ester byproduct by meanso fa n unprecedented reactionm echanism that led to progressive catalystd ecomposition and deactivation (for the mechanistic implications, see below).I nas tudy targetings pecifically the improvement of the co-catalytic component, Cokoja, Kühn, and co-workerse mployed av arietyo fi midazolium bromides such as 17-19,( Scheme 8) and studied the influence on catalytic efficiency of the side chains on the imidazole scaffold. [42] Higher catalytic activity was observed by weakening the interaction between thei onic components of the co-catalytic pair (imidazolium cation and bromide anion)t hus resulting in am ore nucleophilic bromide anion.T his was achieved by alkylating the imidazole backbone at the C2-position. The so-synthesized imidazolium bromide 17 afforded ab etter catalytic performance than C2-unsubstituted species 18 (Scheme 8).…”

Section: Optimization Of the Catalyticpairmentioning

confidence: 98%

Cycloadditions to Epoxides Catalyzed by Group III–V Transition‐Metal Complexes

2015

Self Cite

View full text Add to dashboard Cite

Complexes of group III–V transition metals are gaining increasing importance as Lewis acid catalysts for the cycloaddition of dipolarophiles to epoxides. This review examines the latest reports, including homogeneous and heterogeneous applications. The pivotal step for the cycloaddition reactions is the ring opening of the epoxide following activation by the Lewis acid. Two modes of cleavage (CC versus CO) have been identified depending primarily on the substitution pattern of the epoxide, with lesser influence observed from the Lewis acid employed. The widely studied cycloaddition of CO2 to epoxides to afford cyclic carbonates (CO bond cleavage) has been scrutinized in terms of catalytic efficiency and reaction mechanism, showing that unsophisticated complexes of group III–V transition metals are excellent molecular catalysts. These metals have been incorporated, as well, in highly performing, recyclable heterogeneous catalysts. Cycloadditions to epoxides with other dipolarophiles (alkynes, imines, indoles) have been conducted with scandium triflate with remarkable performances (CC bond cleavage).

show abstract

Section: Optimization Of the Catalyticpairmentioning

confidence: 98%

Cycloadditions to Epoxides Catalyzed by Group III–V Transition‐Metal Complexes

2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…Unlike the case of compound 2, methylation of compound 5 results in the migration of the closest perrhenate anion to the proton of the methylene bridge of the Bn F group (see Fig. 35,36 In contrast to compounds 1 and 2, the insertion of a methyl group at the C2 position of compound 5 does not lead to a contact of perrhenate to the C2 methyl group. This is a result of an increased Lewis acidity of the benzyl methylene protons owing to fluorination of the phenyl ring.…”

Section: X-ray Single Crystal Structure Analysismentioning

confidence: 99%

“…The imidazolium bromide 35,[37][38][39][40][41][42][43][44][45][46] and -perrhenate salts 29 were synthesised according to literature procedures. 1,2-Dimethylimidazole was purchased from Acros Organics.…”

Section: General Remarksmentioning

confidence: 99%

Influence of substituents on cation–anion contacts in imidazolium perrhenates

et al. 2015

Self Cite

View full text Add to dashboard Cite

A series of imidazolium perrhenates with different substituents at the imidazolium ring were synthesised and characterised, including single crystal X-ray diffraction. The effect of the substitution pattern on the state of aggregation of the compounds, the charge delocalisation and the ion pairing interaction via hydrogen bonds was studied. Particularly the substitution at the C2 position of the imidazolium ring was shown to be crucial to fine-tune the ion contacts. Fluorinated substituents appear to exhibit enhanced interionic interactions. The ability to tune the degree of contacts of the perrhenate anion allows for adjusting the nucleophilicity of this anion.

show abstract

“…Among diverse routes to cyclic carbonates, the 100% atom‐economical cycloaddition of readily available epoxides with CO 2 is promising and the most studied methodology, which has been industrialized for more than 50 years. Since Calo et al pioneered the first successful approach to PC synthesis using tetrabutylammonium bromide (TBAB) or tetrabutylammonium iodide (TBAI) at atmospheric CO 2 pressure,14 a plethora of catalytic systems have been developed, including metal‐based catalytic systems, such as metal–organic frameworks (MOFs),15 metal–salen complexes,16 metalloporphyrins,17 metal chloride,18 polyoxometalates (POMs),19 metal oxides; [20] and metal‐free catalysts,21 containing hydroxyls, carboxyls, and so on. From a mechanistic viewpoint, the activation of the epoxide by Lewis acid center or hydrogen‐bond donor play a pivotal role in promoting the cycloaddition reaction, as shown in Scheme .…”

Section: Epoxide/co2 Coupling To Cyclic Carbonatementioning

confidence: 99%

Green Catalytic Process for Cyclic Carbonate Synthesis from Carbon Dioxide under Mild Conditions

Lang

2016

The Chemical Record

100

View full text Add to dashboard Cite

As a renewable and abundant C1 resource possessing multiple attractive characteristics, such as low cost, nontoxicity, non-flammability, and easy accessibility, CO2 conversion into value-added chemicals and fuels can contribute to green chemistry and sustainable development. Since CO2 is a thermodynamically inert molecule, the activation of CO2 is pivotal for its effective conversion. In this regard, the formation of a transition-metal CO2 complex through direct coordination is one of the most powerful ways to induce the inert CO2 molecule to undergo chemical reactions. To date, numerous processes have been developed for efficient synthesis of cyclic carbonates from CO2 . On the basis of mechanistic understanding, we have developed efficient metal catalysts and green processes, including heterogeneous catalysis, and metal-free systems, such as ionic liquids, for cyclic carbonate synthesis. The big challenge is to develop catalysts that promote the reaction under low pressure (preferably at 1 bar). In this context, bifunctional catalysis is capable of synergistic activation of both the substrate and CO2 molecule, and thus, could render CO2 conversion smoothly under mild conditions. Alternatively, converting CO2 derivatives, that is, the captured CO2 as an activated species, would more easily take place at low pressure in comparison with gaseous CO2 . The aim of this Personal Account is to summarize versatile catalytic processes for cyclic carbonate synthesis from CO2 , including epoxide/CO2 coupling reaction, carboxylation of 1,2-diol with CO2 , oxidative cyclization of olefins with CO2 , condensation of vicinal halohydrin with CO2 , carboxylative cyclization of propargyl alcohols with CO2 , and conversion of the CO2 derivatives.

show abstract

Niobium(v) chloride and imidazolium bromides as efficient dual catalyst systems for the cycloaddition of carbon dioxide and propylene oxide

Abstract: Imidazolium bromides combined with niobium(v) choride were used as catalyst system for the reaction of CO2 with epoxides to cyclic carbonates. The variation of the cation structure strongly affects the properties of the imidazolium salt and therefore the catalytic activity.

Cited by 61 publications

References 32 publications

Cycloadditions to Epoxides Catalyzed by Group III–V Transition‐Metal Complexes

Cycloadditions to Epoxides Catalyzed by Group III–V Transition‐Metal Complexes

Influence of substituents on cation–anion contacts in imidazolium perrhenates

Green Catalytic Process for Cyclic Carbonate Synthesis from Carbon Dioxide under Mild Conditions

Contact Info

Product

Resources

About