Asymmetric cycloaddition of CO2 and an epoxide using recyclable bifunctional polymeric Co(iii) salen complexes under mild conditions

Roy, Tamal; Kureshy, Rukhsana I.; Khan, Noor‐ul H.; Abdi, Sayed H. R.; Bajaj, Hari C.

doi:10.1039/c3cy00325f

Cited by 37 publications

(22 citation statements)

References 30 publications

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“…Quaternary ammonium and phosphonium salts or alkali metal halides are typically used as homogeneous catalysts . Other homogeneous catalytic systems, such as ionic liquids (ILs) and salen–metal complexes have also been reported to be effective in the production cyclic carbonates . Difficult isolation procedures for these catalysts necessitates the development of highly efficient heterogeneous catalysts for the synthesis of cyclic carbonates .…”

Section: Introductionmentioning

confidence: 99%

Ionic Polymer Microspheres Bearing a Co^III–Salen Moiety as a Bifunctional Heterogeneous Catalyst for the Efficient Cycloaddition of CO₂ and Epoxides

Leng

Zhang

et al. 2016

Chemistry A European J

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We report a unique strategy to obtain the bifunctional heterogeneous catalyst TBB-Bpy@Salen-Co (TBB=1,2,4,5-tetrakis(bromomethyl)benzene, Bpy=4,4'-bipyridine, Salen-Co=N,N'-bis({4-dimethylamino}salicylidene)ethylenediamino cobalt(III) acetate) by combining a cross-linked ionic polymer with a Co(III) -salen Schiff base. The catalyst showed extra high activity for CO2 fixation under mild, solvent-free reaction conditions with no requirement for a co-catalyst. The synthesized catalyst possessed distinctive spherical structural features, abundant halogen Br(-) anions with good leaving group ability, and accessible Lewis acidic Co metal centers. These unique features, together with the synergistic role of the Co and Br(-) functional sites, allowed TBB-Bpy@Salen-Co to exhibit enhanced catalytic conversion of CO2 into cyclic carbonates relative to the corresponding monofunctional analogues. This catalyst can be easily recovered and recycled five times without significant leaching of Co or loss of activity. Moreover, based on our experimental results and previous work, a synergistic cycloaddition reaction mechanism was proposed.

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Section: Introductionmentioning

confidence: 99%

Ionic Polymer Microspheres Bearing a Co^III–Salen Moiety as a Bifunctional Heterogeneous Catalyst for the Efficient Cycloaddition of CO₂ and Epoxides

Leng

Zhang

et al. 2016

Chemistry A European J

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“…A chloromethyl group also provided a good conversion under our standard reaction conditions with 70 % ee at 40 % conversion for the formation of 2 t ( s =8.9). For this chloromethyl cyclic carbonate 2 t , most studies reported moderate to low s ‐factors below 6,,,,, except for Lu's system, which provided an s ‐factor of 13.2 at a conversion of 41 % . Finally, an epoxide with a quaternary carbon center, 1 u , did not show any reactivity, and styrene oxide afforded the cyclic carbonate 2 v with an s ‐factor of 7.3, compared with an s ‐factor of 5.4 with Lu's catalytic system .…”

Section: Resultsmentioning

confidence: 95%

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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“…[18] (Data are given in the Supporting Information.) The resulting mass was heated at reflux for 3 h (checked by TLC).…”

Section: Methodsmentioning

confidence: 99%

Enantioselective Henry and Aza‐Henry Reaction in the Synthesis of (R)‐Tembamide Using Efficient, Recyclable Polymeric Cu^II Complexes as Catalyst

et al. 2014

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Chiral copper(II) polymeric [H4]salen (salen=bis[(salicylidene)ethylenediaminato]) complexes CuII‐1–3 were generated in situ and used as efficient catalysts in the asymmetric Henry and aza‐Henry reaction of various aromatic and aliphatic aldehydes and N‐tosylimines in the presence of various nitroalkanes at room temperature (27±2 °C) for 20 hours. This group of polymeric [H4]salen complexes demonstrated excellent performance (product yield and enantiomeric excess ee up to 98 %) in the formation of β‐nitroalcohol by using nitromethane with low catalyst loading of 1 mol % (with respect to the monomeric salen unit) and high enantioinduction (ee 94 %) in the aza‐Henry product; β‐nitroamines were obtained with moderate yield (78 %). This catalytic system also worked well with nitroethane and 1‐nitropropane in the case of Henry reaction, to furnish the corresponding products in high yields and enantioselectivities for syn diastereomers. The CuII‐2 complex retained its performance at the gram level and was expediently recycled eight times with no significant loss in its performance. The kinetic study with CuII‐2 complex for the enantioselective aza‐Henry reaction of N‐Ts‐benzylimine (Ts=tosyl) revealed a first‐order dependence on catalyst and nitromethane concentration and was zero order with respect to the substrate. The product obtained was transformed straightforwardly to the pharmaceutically important enantiomerically pure (R)‐tembamide (β‐adrenergic agonist) drug in good yield by the asymmetric nitroaldol reaction of 4‐methoxybenzaldehyde in three successive steps.

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Asymmetric cycloaddition of CO2 and an epoxide using recyclable bifunctional polymeric Co(iii) salen complexes under mild conditions

Cited by 37 publications

References 30 publications

Ionic Polymer Microspheres Bearing a Co^III–Salen Moiety as a Bifunctional Heterogeneous Catalyst for the Efficient Cycloaddition of CO₂ and Epoxides

Ionic Polymer Microspheres Bearing a Co^III–Salen Moiety as a Bifunctional Heterogeneous Catalyst for the Efficient Cycloaddition of CO₂ and Epoxides

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

Enantioselective Henry and Aza‐Henry Reaction in the Synthesis of (R)‐Tembamide Using Efficient, Recyclable Polymeric Cu^II Complexes as Catalyst

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Asymmetric cycloaddition of CO2 and an epoxide using recyclable bifunctional polymeric Co(iii) salen complexes under mild conditions

Cited by 37 publications

References 30 publications

Ionic Polymer Microspheres Bearing a CoIII–Salen Moiety as a Bifunctional Heterogeneous Catalyst for the Efficient Cycloaddition of CO2 and Epoxides

Ionic Polymer Microspheres Bearing a CoIII–Salen Moiety as a Bifunctional Heterogeneous Catalyst for the Efficient Cycloaddition of CO2 and Epoxides

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

Enantioselective Henry and Aza‐Henry Reaction in the Synthesis of (R)‐Tembamide Using Efficient, Recyclable Polymeric CuII Complexes as Catalyst

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Ionic Polymer Microspheres Bearing a Co^III–Salen Moiety as a Bifunctional Heterogeneous Catalyst for the Efficient Cycloaddition of CO₂ and Epoxides

Ionic Polymer Microspheres Bearing a Co^III–Salen Moiety as a Bifunctional Heterogeneous Catalyst for the Efficient Cycloaddition of CO₂ and Epoxides

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

Enantioselective Henry and Aza‐Henry Reaction in the Synthesis of (R)‐Tembamide Using Efficient, Recyclable Polymeric Cu^II Complexes as Catalyst