Green Chemistry Blog

A continuous flow Barbier reaction was employed for the production of a key pharmaceutical intermediate (1) in the synthesis of edivoxetine·HCl (a highly selective norepinephrine re-uptake inhibitor).

US scientists from Eli Lilly and Company and D&M Continuous Solutions, led by Michael Kopach, report the development of a continuous Barbier reaction which preserves chirality and the product obtained in >99% ee.  The team ran the process in a series of continuous stirred tank reactors, where residence time, solvent composition, stoichiometry and operations temperature were optimised to produce 12 g per hour of the ketone precursor to 1 with 98% ee and 88% in situ yield for 47 hours total flow time.  Continuous salt formation and isolation of 1 could then be achieved from the ketone solution with >99% purity.

This process offers up several significant advantages over a traditional Grignard batch process.  This continuous flow method gave greater than 30% reduced process mass intensity and magnesium usage relative to the batch method.  Equally, the flow process resulted in >100 x less excess magnesium to quench and >100 x less diisobutylaluminum hydride to initiate giving significant safety benefits.  The authors expect that the maximum long-term scale of the process is 50 L which would replace 4000-6000 L batch reactors.

This article is free to access until the 11th May 2012! Click on the link below to find out more…

The continuous flow Barbier reaction: an improved environmental alternative to the Grignard reaction?, Michael E. Kopach, Dilwyn J. Roberts, Martin D. Johnson, Jennifer McClary Groh, Jonathan J. Adler, John P. Schafer, Michael E. Kobierski and William G. Trankle, Green Chem., 2012, DOI: 10.1039/C2GC35050E

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Development of safe and scalable continuous-flow methods for palladium-catalyzed aerobic oxidation reactions, Xuan Ye, Martin D. Johnson, Tianning Diao, Matthew H. Yates and Shannon S. Stahl, Green Chem., 2010, 12, 1180-1186

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French scientists have investigated the mechanisms involved in producing mixed bio/fossil fuels and the fate of the bio-carbon during the process.

In order to meet the regulation constraints for transportation fuels set by the European Commission, a promising solution is to produce mixed bio/fossil fuels by co-processing biomass pyrolysis oil with crude oil fractions (obtained from distillation in a standard oil refinery).  In previous work, Yves Schuurman and colleagues from the University of Lyon, France, showed that gasoline could be produced by co-processing hydrodeoxygenated pyrolysis oil with conventional vacuum gas oil in a lab-scale fluid catalytic cracking (FCC) unit.  However, up till now, accurate determination of the proportion of renewable molecules in the target product to be commercialised, i.e. gasoline, has not be preformed, but is very important for technical and marketing reasons. 

In this work, the Carbon-14 (¹⁴C) method was used to determine bio-carbon content in FCC products.  While fossil fuel is virtually ¹⁴C-free, biofuels contain the present-day ‘natural’ levels of ¹⁴C.  The results from this study have given valuable information on the co-processing mechanism, and the authors show that co-processing bio-oil with fossil fuel resources leads to bio-carbon impoverished gasoline but bio-carbon enriched liquefied petroleum gas.

This article is free to access until 3rd May 2012!  Click on the link below to find out more…

The fate of bio-carbon in FCC co-processing products, Gabriella Fogassy, Nicolas Thegarid, Yves Schuurman and Claude Mirodatos, Green Chem., 2012, DOI: 10.1039/C2GC35152H

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Scientists from Singapore have employed an ionic liquid to fabricate polybenzimidazole (PBI) membranes for protein separation and water reuse.

PBI has been extensively investigated in the field of membrane separation technologies due to its high glass transition temperature, stable thermal properties and excellent chemical resistance in harsh environments.   One major drawback of PBI though is its low solubility.  Only a few highly polar and aprotic organic solvents are able to dissolve PMI (such as DMSO, DMF and N,N-dimethylacetamide), but these are relatively toxic and volatile.

Here, the team from the National University of Singapore led by Tai-Shung Chung found that 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) was able to dissolve PBI under much lower temperatures and pressures compared to traditional solvents.  The acetate anion of the ionic liquid could form hydrogen bonds with the PBI chains, effectively breaking the interchain bonding in PBI. Ultrafiltration membranes could then be made from the PBI-[EMIM]OAc solution by a non-solvent induced phase separation method, with the resulting membranes achieving a high separation factor. 

This article is free to access until the 27th April 2012!  Click on the link below to find out more…

Molecular interactions between polybenzimidazole and [EMIM]OAc, and derived ultrafiltration membranes for protein separation, Ding Yu Xing ,  Sui Yung Chan and Tai-Shung Chung, Green Chem., 2012, DOI: 10.1039/C2GC35134J  

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Scientists have developed an efficient peroxophosphotungstate-based polymer-immobilised ionic liquid phase catalyst for the epoxidation of allylic alcohols and alkenes.

Polyoxometalates (POMs) have been shown to be efficient Bronsted acid catalysts and selective oxidation catalysts in various important transformations.  Research in recent years has been focused on surface immobilisation of POMs in order to develop continuous flow process and improve the robustness and recyclability of the catalysts and to avoid or reduce catalyst leaching.

In this work, scientists from Newcastle University and Queen’s University, Belfast led by Simon Doherty, Julian Knight and Christopher Hardacre prepared a linear cation-decorated polymeric support with tuneable surface properties and microstructure by ring-opening metathesis polymerisation of a norbornene-based monomer with cyclooctene.  The resulting peroxophosphotungstate-based polymer-supported ionic liquid phase catalyst presented an efficient system for the epoxiadation of allylic alcohols and alkenes.  Importantly, the catalysts could be easily recovered and reused with only a slight reduction in performance. 

This article is free to access until the 19th April 2012!  Click on the link below to find out more…

An efficient recyclable peroxometalate-based polymer-immobilised ionic liquid phase (PIILP) catalyst for hydrogen peroxide-mediated oxidation, Simon Doherty, Julian G. Knight, Jack R. Ellison, David Weekes, Ross W. Harrington, Christopher Hardacre and Haresh Manyar, Green Chem., 2012, DOI: 10.1039/C2GC16679H