Controlled Synthesis of the Henry Reaction Products: Nitroalcohol Versus Nitrostyrene by a Simple Change of Amino-Groups of Aminofunctionalized Nanoporous Catalysts

Anan, Abhishek; Vathyam, Rajyalakshmi; Sharma, Krishna K.; Asefa, Tewodros

doi:10.1007/s10562-008-9595-1

Cited by 43 publications

(27 citation statements)

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“…[25,26] Solin and collaborators, as well as Thiel and co-workers, obtained similar results, using different combinations of alkylamines and acidic groups in mesoporous silica supports. [23,27] However, the poor catalytic activity of monofunctional amine on silica, which remains commonly used for the aldol and similar types of condensation, [20,22,24,[29][30][31][32] is still not well understood.…”

Section: Introductionmentioning

confidence: 99%

Substrate inhibition in the heterogeneous catalyzed aldol condensation: A mechanistic study of supported organocatalysts

Kandel

Althaus

Peeraphatdit

et al. 2012

Journal of Catalysis

137

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In this study, we demonstrate how materials science can be combined with the established methods of organic chemistry to find mechanistic bottlenecks and redesign heterogeneous catalysts for improved performance. By using solid-state NMR, infrared spectroscopy, surface and kinetic analysis, we prove the existence of a substrate inhibition in the aldol condensation catalyzed by heterogeneous amines. We show that modifying the structure of the supported amines according to the proposed mechanism dramatically enhances the activity of the heterogeneous catalyst. We also provide evidence that the reaction benefits significantly from the surface chemistry of the silica support, which plays the role of a co-catalyst, giving activities up to two orders of magnitude larger than those of homogeneous amines. This study confirms that the optimization of a heterogeneous catalyst depends as much on obtaining organic mechanistic information as it does on controlling the structure of the support. Disciplines Materials Chemistry | Other Chemistry | Physical ChemistryComments NOTICE: this is the author's version of a work that was accepted for publication in Journal of Catalysis. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Catalysis, [291, (2012) AbstractIn this study we demonstrate how materials science can be combined with the established methods of organic chemistry to find mechanistic bottlenecks and redesign heterogeneous catalysts for improved performance. By using solid-state NMR, infrared spectroscopy, surface and kinetic analysis, we prove the existence of a substrate inhibition in the aldol condensation catalyzed by heterogeneous amines. We show that modifying the structure of the supported amines according to the proposed mechanism dramatically enhances the activity of the heterogeneous catalyst. We also provide evidence that the reaction benefits significantly from the surface chemistry of the silica support, which plays the role of a co-catalyst, giving activities up to two orders of magnitude larger than those of homogeneous amines. This study confirms that the optimization of a heterogeneous catalyst depends as much on obtaining organic mechanistic information as it does on controlling the structure of the support.

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Section: Introductionmentioning

confidence: 99%

Substrate inhibition in the heterogeneous catalyzed aldol condensation: A mechanistic study of supported organocatalysts

Kandel

Althaus

Peeraphatdit

et al. 2012

Journal of Catalysis

137

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“…The Knoevenagel reaction has been conducted with aminopropylfunctionalized MCM-41-type mesoporous silica, [95] and interestingly, the understanding gained within this reaction marked the starting point to elucidate the role of the outer-sphere polarity surrounding a tethered catalyst on the chemical reactivity of the heterogeneous catalyst. [96,97] In this framework, Reddy et al reported the use of chitosan hydrogel microspheres for the Knoevenagel reaction of a set of aromatic aldehydes (para-nitrobenzaldehyde, para-chlorobenzaldehyde, naphthaldehyde, para-tolualdehyde, and paramethoxybenzaldehyde) by using three different activated methylenes (malonitrile, ethylcyanoacetate, and diethylmalonate; Scheme 5). [98] With DMSO as a solvent, and at room temperature, the reactants readily condense to provide the expected dehydrated products in good yields and selectivity.…”

Section: Knoevenagel Reactionmentioning

confidence: 99%

Chitosan as a Sustainable Organocatalyst: A Concise Overview

Kadib

2014

ChemSusChem

209

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Increased demand for more sustainable materials and chemical processes has tremendously advanced the use of polysaccharides, which are natural biopolymers, in domains such as adsorption, catalysis, and as an alternative chemical feedstock. Among these biopolymers, the use of chitosan, which is obtained by deacetylation of natural chitin, is on the increase due to the presence of amino groups on the polymer backbone that makes it a natural cationic polymer. The ability of chitosan-based materials to form open-network, macroporous, high-surface-area hydrogels with accessible basic surface sites has enabled their use not only as macrochelating ligands for active metal catalysts and as a support to disperse nanosized particles, but also as a direct organocatalyst. This review provides a concise overview of the use of native and modified chitosan, possessing different textural properties and chemical properties, as organocatalysts. Organocatalysis with chitosan is primarily focused on carbon-carbon bond-forming reactions, multicomponent heterocycle formation reactions, biodiesel production, and carbon dioxide fixation through [3+2] cycloaddition. Furthermore, the chiral, helical organization of the chitosan skeleton lends itself to use in enantioselective catalysis. Chitosan derivatives generally display reactivity similar to homogeneous bases, ionic liquids, and organic and inorganic salts. However, the introduction of cooperative acid-base interactions at active sites substantially enhances reactivity. These functional biopolymers can also be easily recovered and reused several times under solvent-free conditions. These accomplishments highlight the important role that natural biopolymers play in furthering more sustainable chemistry.

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“…In particular, mesoporous silica-supported amines have been widely shown to serve as heterogeneous catalysts for the Henry reactions between various substituted benzaldehydes and nitroalkanes. [50][51][52][53][54][55] The products of these reactions were reported to be predominantly the dehydrated C-C coupling products such as substituted nitrostyrenes. In some instances or under some reaction conditions, however, the Henry reaction could generate the nondehydrated products or even the Michael addition products.…”

Section: Henry Reactionmentioning

confidence: 99%