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Steines, Stephan; Wasserscheid, Peter; Drießen‐Hölscher, Birgit

doi:10.1002/(sici)1521-3897(200004)342:4<348::aid-prac348>3.3.co;2-y

Cited by 17 publications

(28 citation statements)

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“…Based on investigations in the biphasic system water/n-heptane, [71] the ruthenium-catalyzed hydrogenation of sorbic acid to cis-3-hexenoic acid according to Equation (10) in the system [BMIM]PF 6 /MTBE (MTBE methyl tert-butyl ether) was REVIEWS P. Wasserscheid and W. Keim studied. [72] In comparison to other polar solvents (e.g. glycol) a more than threefold increase in activity with comparable selectivity to cis-3-hexenoic acid was observed in the ionic liquid.…”

Section: Hydrogenationsmentioning

confidence: 95%

Ionic Liquids—New “Solutions” for Transition Metal Catalysis

Wasserscheid

Keim

2000

Angew. Chem. Int. Ed.

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5,629

3,133

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Ionic liquids are salts that are liquid at low temperature (<100 °C) which represent a new class of solvents with nonmolecular, ionic character. Even though the first representative has been known since 1914, ionic liquids have only been investigated as solvents for transition metal catalysis in the past ten years. Publications to date show that replacing an organic solvent by an ionic liquid can lead to remarkable improvements in well‐known processes. Ionic liquids form biphasic systems with many organic product mixtures. This gives rise to the possibility of a multiphase reaction procedure with easy isolation and recovery of homogeneous catalysts. In addition, ionic liquids have practically no vapor pressure which facilitates product separation by distillation. There are also indications that switching from a normal organic solvent to an ionic liquid can lead to novel and unusual chemical reactivity. This opens up a wide field for future investigations into this new class of solvents in catalytic applications.

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Section: Hydrogenationsmentioning

confidence: 95%

Ionic Liquids—New “Solutions” for Transition Metal Catalysis

Wasserscheid

Keim

2000

Angew. Chem. Int. Ed.

Self Cite

5,629

3,133

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“…28 More recently, the ruthenium-catalysed hydrogenation of sorbic acid to cis-hex-3-enoic acid (Reaction 1) was achieved in a biphasic bmimPF 6 -methyl tert-butyl ether system. 29 (1)…”

Section: Hydrogenationmentioning

confidence: 99%

Untitled

2001

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The chemical industry is under considerable pressure to replace many of the volatile organic compounds (VOCs) that are currently used as solvents in organic synthesis. The toxic and/or hazardous properties of many solvents, notably chlorinated hydrocarbons, combined with serious environmental issues, such as atmospheric emissions and contamination of aqueous effluents is making their use prohibitive. This is an important driving force in the quest for novel reaction media. Curzons and coworkers, for example, recently noted that rigorous management of solvent use is likely to result in the greatest improvement towards greener processes for the manufacture of pharmaceutical intermediates. The current emphasis on novel reaction media is also motivated by the need for efficient methods for recycling homogeneous catalysts. The key to waste minimisation in chemicals manufacture is the widespread substitution of classical 'stoichiometric' syntheses by atom efficient, catalytic alternatives. In the context of homogeneous catalysis, efficient recycling of the catalyst is a conditio sine qua non for economically and environmentally attractive processes. Motivated by one or both of the above issues much attention has been devoted to homogeneous catalysis in aqueous biphasic and fluorous biphasic systems as well as in supercritical carbon dioxide. Similarly, the use of ionic liquids as novel reaction media may offer a convenient solution to both the solvent emission and the catalyst recycling problem.

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“…The highest rate and stereoselectivity have been obtained with the "naked" [Cp*Ru] -that is, a monocyclopentadiene-ruthenium complex without any additional, inhibiting ligands and [Cp*Ru(g 4 -sorbic acid)] + X -(52) (sorbic acid = (2E,4E)-MeCH=CHCH=CHCO 2 H and X = CF 3 SO 3 -or BARF -) displays the best results. These ionic ruthenium catalysts have been used successfully in a single phase as well as liquid two-phase systems (such as liquid-liquid, ionic liquid-liquid solvent systems) [66,67]. The activity of these catalysts depends strongly on the solvent or solvent mixtures used, with the rate of hydrogenation of sorbic acid (in TOF) ranging from 92 to 1057 mol mol -1 h -1 .…”

Section: Ruthenium Catalystsmentioning

confidence: 99%