Catalytic Organic Reactions in Water toward Sustainable Society

Abstract

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 solution from a product that is soluble in organic solvents. In contrast, the use of heterogeneous catalysts facilitates catalyst recycling by allowing simple centrifugation and filtration methods to be used. This Review addresses advances over the past decade in catalytic reactions using water as a reaction medium.

Dehydrative Synthesis of Functionalized Skipped Dienes from Stabilized Phosphonium Ylides and Allylic Alcohols in Water

“…Based on these control experiments and the literature reports, [8][9][22][23][24] a possible reaction mechanism was depicted in Scheme 2.…”

Solid-Supported Palladium Catalysts in Sonogashira Reactions: Recent Developments

“…The recycled catalyst was reused for five runs observing almost no loss of effectivity. The use of water as solvent adds an "environmentally-friendly" tag when a catalytic methodology is developed [23], and its combination with recoverable catalysts from polystyrene results particularly interesting for economic and industrial purposes. Thus, polystyrene-anchored Pd(II) pyridine complex 8 ( Figure 3) has been used as catalyst in the copper-free coupling of aryl iodides, bromides and chlorides with some terminal alkynes, in water and at room temperature, the chloride derivatives affording just moderate yields.…”

A New Mn-Salen Micellar Nanoreactor for Enantioselective Epoxidation of Alkenes in Water

“…However, the use of water as solvent for organic synthesis is limited by the low solubility of organic compounds and the facile decomposition of many active species in water. This drawback was recently resolved by the use of nanocapsular systems [2] and micelles [3], which dissolved and stabilized organic substrates in water and, in some examples, act as molecular reactors for organic synthesis [4].…”

“…In this context, many efforts have been addressed to leave the "poor ecofriendly conditions" (e.g. the use of organic solvent and reaction with strong conditions), moving towards more efficient and eco compatible reactions, by using efficient heterogeneous catalysts [7] and/or reactions in aqueous media [3]. However, few examples of enantioselective epoxidation in water are reported in Literature [8].…”