Native and modified chitosan-based hydrogels as green heterogeneous organocatalysts for imine-mediated Knoevenagel condensation

Franconetti, Antonio; Domínguez-Rodríguez, Pedro; Lara-García, Dolores; Prado‐Gotor, Rafael; Cabrera‐Escribano, Francisca

doi:10.1016/j.apcata.2016.03.012

Cited by 36 publications

(19 citation statements)

References 40 publications

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“…The band at 564 cm ‐1 ascribed to Mo‐N bond further signifies the complexation of metal with chitosan through –NH 2 group ,,,. The 465 cm ‐1 band in the complex is due to Mo‐O bond in the complex ,,,…”

Section: Resultsmentioning

confidence: 99%

Selective and Green Sulfoxidation in Water using a New Chitosan Supported Mo(VI) Complex as Heterogeneous Catalyst

et al. 2018

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Immobilization of oxo‐peroxo molybdenum(VI) species on natural biopolymer, chitosan led to the development of a new heterogeneous catalyst which displayed excellent activity, stability and chemoselectivity for the oxidation of a wide variety of sulfides to the respective sulfoxides by H2O2 in water, at ambient temperature. The catalyst has been comprehensively characterized by elemental analysis, spectral studies (FTIR, Raman, solid‐state 13C NMR and diffuse reflectance UV‐Vis), PXRD, Brunauer‐Emmett‐Teller (BET), SEM, EDX and TGA‐DTG analysis. The density functional theory (DFT) method has been employed to study the structure of the synthesized chitosan peroxomolybdenum complex (PMoCh). In addition to water, the catalyst is also highly compatible with a variety of safer organic solvents like methanol and acetonitrile. Apart from being high yielding and operationally simple, the developed catalytic protocol is environmentally clean and safe as it is absolutely free from halogenated organic solvent. Other significant green attributes of the methodology include its ready scalability, high H2O2 efficiency and easy recyclability of the catalyst for several catalytic cycles with consistent activity/selectivity profile.

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Section: Resultsmentioning

confidence: 99%

Selective and Green Sulfoxidation in Water using a New Chitosan Supported Mo(VI) Complex as Heterogeneous Catalyst

et al. 2018

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“…In 2016, Cabrera‐Escribano and co‐workers reported an extensive study on chitosan‐catalyzed Knoevenagel reactions with malononitrile and ethyl cyanoacetate, expanding the substrate scope to more challenging and complex aromatic and heteroaromatic aldehydes . Native chitosan hydrogel beads and hydrogel disks of ureidyl‐chitosan derivative 20 were evaluated as effective heterogeneous catalysts in DMSO at room temperature (Scheme ).…”

Section: Natural Polysaccharide‐based Organocatalystsmentioning

confidence: 99%

Valorization of Waste: Sustainable Organocatalysts from Renewable Resources

Meninno

2019

ChemSusChem

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443 Reviews Figure 2. Potential organocatalytic modes of activatione xhibited by chitosan.Scheme2.Monoglycerides ynthesis by ring opening of the glycidol catalyzed by chitosan. 444 ReviewsScheme3.Aldol reaction between 4-nitrobenzaldehyde (1)a nd cyclohexanone (2)promoted by chitosan hydrogel beads. Scheme4.Aldol reactionscatalyzed by dried chitosan gels and proposed catalytic modes of activation. 445 Reviews Scheme5.Aldol reaction in water promoted by chitosan aerogel beads (additivesu sed at 20 mol %: DNP = 2,4-dinitrophenol, SA = stearic acid, SDS = sodium dodecyl sulfate,B oc = tert-butyloxycarbonyl; ee = enantiomeric excess). Scheme6.Aldol reactionscatalyzedb yc hitosan in 1-butyl-3-methylimidazolium bromide ([bmim][Br])at3 78C. 446 Reviews Scheme16. Asymmetric aldol reaction in water catalyzedb yc hitosan-supported cinchonine. Scheme15. Chitosan-catalyzed transamidation of carboxamides with amines under neat conditions. 450 Reviews Scheme17. Knoevenagelcondensation of challenging aldehydes promoted by native and modified chitosan-derived hydrogels ([a] conversion valuesare reported). 458 Reviews Scheme33. Stereoselective Michael reaction catalyzedbyan aturalpinanederived bifunctional organocatalyst. Scheme32. Stereoselective Mannich reaction catalyzed by d-glucosamine-derived organocatalyst and the hypothetical reaction TS. 460 Reviews Scheme35. a) Synthesis of organocatalyst 52 derived from abietic acid. b) Asymmetric direct aldol reaction catalyzed by 52.c)Proposed TS model. 461 ReviewsScheme42. a) Reductive transformation of CO 2 with amines into formamidesand methylamines organocatalyzedbyl ecithin, and b) plausible reaction mechanism.

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“…Application of the general procedure to CS 1 (200 mg) and 3-trifluoromethylphenyl isocyanate (250 µL, 1.8 mmol), after 120 h (pH 6.0), afforded compound I (177 mg) as a white solid (Franconetti, et al, 2016). DS: 0.14.…”

Section: N-(3-trifluoromethylphenylcarbamoyl)chitosan Imentioning

confidence: 99%

“…From a catalytic perspective, chitosan can be used following two strategies, that is, directly as a heterogeneous catalyst or as a platform supporting the corresponding organocatalyst. For the first strategy, native chitosan hydrogels have proved to be an effective catalyst for Knoevenagel reactions (Franconetti, Domínguez-Rodríguez, Lara-García, Prado-Gotor, & Cabrera-Escribano, 2016), aldol reactions and Henry reactions, among others (Kühbeck, Saidulu, Reddy, & Díaz-Díaz, 2012). Chitosan derivatives have also served as a valuable support for several types of organocatalysts (Chtchigrovsky, et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Preparation of chitosan-supported urea materials and their application in some organocatalytic procedures

Gonzalo

Franconetti

Fernández

et al. 2018

Carbohydrate Polymers

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An efficient and mild procedure was developed for the preparation of three chitosan-supported ureas containing electron-withdrawing groups. These catalysts were characterized and employed as organocatalysts in different transformations, including the enantioselective cyanosilylation of α-ketoesters and aldehydes, the asymmetric addition of formaldehyde tert-butyl hydrazone to prochiral α-ketoesters and a Friedel-Crafts reaction. Several parameters that can affect the activity and selectivity of the reactions were analysed. The supported catalysts can be reused for more than 10 cycles with only a small loss in their properties. Finally, theoretical DFT calculations were carried out to interpret the results of the catalysed reactions.

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Native and modified chitosan-based hydrogels as green heterogeneous organocatalysts for imine-mediated Knoevenagel condensation

Cited by 36 publications

References 40 publications

Selective and Green Sulfoxidation in Water using a New Chitosan Supported Mo(VI) Complex as Heterogeneous Catalyst

Selective and Green Sulfoxidation in Water using a New Chitosan Supported Mo(VI) Complex as Heterogeneous Catalyst

Valorization of Waste: Sustainable Organocatalysts from Renewable Resources

Preparation of chitosan-supported urea materials and their application in some organocatalytic procedures

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