The E factor 25 years on: the rise of green chemistry and sustainability

Traditional organic synthesis relies heavily on organic solvents for a multitude of tasks, including dissolving the components and facilitating chemical reactions, because many reagents and reactive species are incompatible or immiscible with water. Given that they are used in vast quantities as compared to reactants, solvents have been the focus of environmental concerns. Along with reducing the environmental impact of organic synthesis, the use of water as a reaction medium also benefits chemical processes by simplifying operations, allowing mild reaction conditions, and sometimes delivering unforeseen reactivities and selectivities. After the “watershed” in organic synthesis revealed the importance of water, the development of water-compatible catalysts has flourished, triggering a quantum leap in water-centered organic synthesis. Given that organic compounds are typically practically insoluble in water, simple extractive workup can readily separate a water-soluble homogeneous catalyst as an aqueous so...

Catalytic Organic Reactions in Water toward Sustainable Society

The metal-catalysed successive activation and functionalisation of sp2 C–H bonds is the at heart of synthetic innovations for the development of C–C bond cross-coupling processes. Against expectation catalytic C–H bond transformations can be performed in water as an available, renewable, safe solvent but most importantly as a partner improving the catalyst activity. The objective of the review is to present the catalytic successes for C–H bond transformations in water, discovered mainly during the last six years and involving mostly palladium and ruthenium catalysts, often with the help of a carboxylate partner for the initial key C–H bond deprotonation. Water is beneficial for the direct catalytic arylation with (hetero)aryl halides of functional arene ortho C–H bonds with pyridine, pyrazole, oxazoline, imine, urea, amide… directing groups leading to functional biaryl derivatives, polyheterocycles and polydentate ligands. Metal-catalysed activation of the sp2 C–H bond in water also allows the cross-coupling reaction of two different C–H bonds in the presence of an oxidant and regioselective alkenylations of arenes, heterocycles and functional alkenes are now controlled. Annulation reactions via insertion of alkynes into both activated C–H and heteroatom–hydrogen bonds in water constitute new routes to heterocycles.

sp2 C–H bond activation in water and catalytic cross-coupling reactions

Recent advances in catalysis in micellar media

Mimicking the Cell: Bio-Inspired Functions of Supramolecular Assemblies

An environmentally benign surfactant (TPGS-750-M), a diester composed of racemic α-tocopherol, MPEG-750, and succinic acid, has been designed and readily prepared as an effective nanomicelle-forming species for general use in metal-catalyzed cross-coupling reactions in water. Several “name” reactions, including Heck, Suzuki−Miyaura, Sonogashira, and Negishi-like couplings, have been studied using this technology, as have aminations, C−H activations, and olefin metathesis reactions. Physical data in the form of DLS and cryo-TEM measurements suggest that particle size and shape are key elements in achieving high levels of conversion and, hence, good isolated yields of products. This new amphiphile will soon be commercially available.

/pdf/tpgs-750-m-a-second-generation-amphiphile-for-metal-3c201c50bs.pdf

TPGS-750-M: a second-generation amphiphile for metal-catalyzed cross-couplings in water at room temperature.

The remarkable effects of added salts on the properties of aqueous micelles derived from the amphiphile PTS are described. Most notably, Heck reactions run in the presence of NaCl lead to couplings on aryl bromides in water at room temperature. Olefin cross- and ring-closing metathesis reactions run in the presence of small amounts of pH-lowering KHSO4 are also accelerated, another phenomenon that does not apply to typical processes in organic media. These salt effects allow, in general, for synthetically valuable C–C bond-forming processes to be conducted under environmentally benign conditions. Recycling of the surfactant is also demonstrated.

/pdf/manipulating-micellar-environments-for-enhancing-transition-4b6yhb237f.pdf

Manipulating Micellar Environments for Enhancing Transition Metal-Catalyzed Cross-Couplings in Water at Room Temperature

Organocatalysis in water at room temperature with in-flask catalyst recycling.

Described herein are newly developed, straightforward entries to polyethyleneglycol ubiquinol succinate (PQS, n = 2), a designer surfactant that serves as precursor to micelle-forming, covalently bound catalysts for a variety of transformations in water with in-flask catalyst recycling.

Subir Ghorai

Papers

TPGS-750-M: a second-generation amphiphile for metal-catalyzed cross-couplings in water at room temperature.

Manipulating Micellar Environments for Enhancing Transition Metal-Catalyzed Cross-Couplings in Water at Room Temperature

Organocatalysis in water at room temperature with in-flask catalyst recycling.

Modified routes to the "designer" surfactant PQS.

Tandem olefin metathesis–elimination reactions. A new route to doubly unsaturated carbonyl derivatives