Green Chemistry Considerations in Entropic Control of Materials and Processes

Trakhtenberg, Sofia; Warner, John C.

doi:10.1021/cr0509455

Cited by 18 publications

(10 citation statements)

References 57 publications

(89 reference statements)

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“…46 More recently, the potential of 'entropic control' with respect to the imperatives of Green Chemistry has been emphasized. 55 Through studies of an ytterbium(III) triflate/amino acid catalyzed Michael addition under aqueous biphasic conditions, we have discovered that the enantioselectivity of the reaction can be significantly altered, and even reversed, simply by modifying the reaction temperature. Although the microscopic details behind the effects observed are still unclear, the body of data we have presented herein point to the importance of an unusually large entropy factor, which leads to a delicate balance between enthalpy and entropy contributions to the Gibbs energies of equilibrating activated complexes in the enantiodifferentiating step.…”

Section: Discussionmentioning

confidence: 99%

Entropy-Controlled and Enantiodivergent Lewis Acid Catalysis in Water

Aplander¹,

Lindström²,

Wennerberg³

2012

Synthesis

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Developing new and useful methods in asymmetric catalysis is of continuous importance. A current challenge is to address the imperatives of green chemistry, such that processes maximize resource-efficiency and minimize the generation of waste. To this end, this article discloses the potential of a-amino acids in the development of entropy-controlled and enantiodivergent Lewis acid catalysis. In an ytterbium-catalyzed aqueous Michael addition reaction, natural a-amino acids induced not only a large rate acceleration, but also an unusual and remarkable reversed temperature effect on enantioselectivity. As demonstrated with 17 aamino acids, the enantioselectivity of the reaction can be significantly altered, and even reversed, simply by modifying the reaction temperature. After determining differential thermodynamic activation parameters, it was revealed that an unusually large entropy contribution was responsible for the observed effects. By further correlation to the influence of the aqueous medium, we put forward the concept of stereospecific aqueous solvation (SAS), which describes the bearing of aqueous solvation on the equilibrium of diastereomeric transition states, and thus on the R/S ratio of the product.

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Section: Discussionmentioning

confidence: 99%

Entropy-Controlled and Enantiodivergent Lewis Acid Catalysis in Water

Aplander¹,

Lindström²,

Wennerberg³

2012

Synthesis

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“…There is excellent potential for eliminating pollution associated with the solvents, purification steps, and energy inputs needed for covalent chemistry. The use of supramolecular aggregates in Polaroid Instant Photography is an example of the viability of non-covalent chemistry on the industrial scale (63,64). Carbon dioxide (CO 2 ), an abundant and cheap waste material, has been extensively studied as a replacement for conventional solvents.…”

Section: Alternative Solventsmentioning

confidence: 99%

Green chemistry: the emergence of a transformative framework

Anastas

Beach

2007

Green Chemistry Letters and Reviews

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Since the Twelve Principles of Green Chemistry were formulated in the 1990s, there have been tremendous successes in developing new products and processes to be more compatible with human health, the environment, and sustainability goals. This review gives a sampling of research successes from the last 20 years, including advances in synthetic efficiency, application of alternative synthetic methods, use of less hazardous solvents and reagents, and development of renewable resources for chemical feedstocks. The future of green chemistry will depend on innovations that consolidate and integrate these achievements that have been made, using all Twelve Principles as a framework for intentional design. Designing for sustainability and reduced hazard should not be viewed as constraining, but rather as providing the freedom to explore and invent, bridging continents and scientific disciplines to create new solutions.

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“…For this, the synthesis of robust, readily available, and active catalysts is necessary and it has become a very imperative topic for scientists working across all disciplines. 1–3 Moreover, it is extremely favorable that the catalytic protocols involve suitable synthetic routes based on naturally sourced catalysts. Learning from nature, employing biomolecules is highly desirable in chemical transformations.…”

Section: Introductionmentioning

confidence: 99%