Green Chemistry Blog

UK scientists have developed a continuous photo-oxidation procedure of an allylic alcohol in supercritical carbon dioxide.

Malaria is one of the most infectious diseases in the world.  Some strains of malaria are becoming resistant to the traditionally used quinine based antimalarials, and so there is a need to develop new antimalarial drugs.  A common feature of some newly developed antimalarial compounds is the trioxane moiety, and a convenient way to introduce this group is via photochemically generated singlet oxygen species (¹O₂).  However the highlight reactive nature of this species can introduce problems when trying to scale-up the synthesis of these groups for industrial production, particularly in terms of identifying acceptable solvents (non-flammable and in-efficient ¹O₂ quenchers).

In this work, Martyn Poliakoff, Michael George and colleagues from the University of Nottingham, UK, have developed a continuous process for the sustainable synthesis of trioxones with  ¹O₂in supercritical CO₂.  The team also examined the remaining two steps in the synthesis of antimalarial trioxanes from readily available starting materials, and hope that this approach could lead to the exploration of libraries of different trioxanes as potential antimalarial agents.

Read the full article for free until the 9th January 2013!

Synthesis of antimalarial trioxanes via continuous photo-oxidation with ¹O₂ in supercritical CO₂, Jessica F. B. Hall, Richard A. Bourne, Xue Han, James H. Earley, Martyn Poliakoff and Michael W. George, Green Chem., 2013, DOI: 10.1039/C2GC36711D

You may also be interested in this article which is also free to access for a limited time:

Could the energy cost of using supercritical fluids be mitigated by using CO2 from carbon capture and storage (CCS)? James G. Stevens, Pilar Gómez, Richard A. Bourne, Trevor C. Drage, Michael W. George and Martyn Poliakoff, Green Chem., 2011, 13, 2727-2733

Stay up-to-date with the latest news and content in Green Chemistry by registering for our free table of contents alerts.

Biocatalysis is becoming an increasingly attractive method to achieve enantiopure chemicals, in a cleaner and more environmentally sustainable way.  This is in part due to the fact that in most of these reactions, water is used as the solvent primarily because the enzyme catalysts are most stable in this medium.  However, some substrates are insoluble or only sparingly soluble in water which can limit the use of these enzymes.

In this work, Lasse Greiner and colleagues from Germany have developed a procedure whereby sparingly water-soluble long-chain ketones can be reduced in a continuous process.  The authors used an ionic liquid as a detergent to increase the solubility of these substrates and products, and ultrafiltration in an enzyme membrane reactor was employed to increase the enzyme utilization.  A cascade of two enzyme membrane reactors was configured which could run for more than 1000 hours with high turnover numbers and 99.9% enantioselectivity.

Finally, downstream adsorption of the resulting alcohols allowed 90% recycling of the aqueous buffer solution, reducing the E-factor of the process to 13.

This article is currently free to access until the 3rd January 2013!

Enantioselective reduction of sparingly water-soluble ketones: continuous process and recycle of the aqueous buffer system, Susanne Leuchs, Shukrallah Na’amnieh and Lasse Greiner, Green Chem., 2013, DOI: 10.1039/C2GC36558H

You may also be interested in these articles as well – free to access for 2 weeks:

Utilising hardly-water soluble substrates as a second phase enables the straightforward synthesis of chiral alcohols, Christina Kohlmann, Nora Robertz, Susanne Leuchs, Lasse Greiner and Shukralla Na’amnieh, Green Chem., 2011, 13, 3093-3095

Continuous biocatalytic synthesis of (R)-2-octanol with integrated product separation, Christina Kohlmann, Susanne Leuchs, Lasse Greiner and Walter Leitner, Green Chem., 2011, 13, 1430-1436

Stay up-to-date with the latest news and content in Green Chemistry by registering for our free table of contents alerts.

Scientists from Germany employed a mechanochemical approach to cleave β-O-4-linkages in lignin.

In recent years, plant biomass has come to the fore due to it’s potential to replace fossil-fuel derived chemicals.  Lignin is one of the three main constituents of biomass, but it’s use is hampered by its poor solubility and structural complexity. The β-O-4-linkage is the most abundant linkage found in lignin, and attempts to cleave them currently employ harsh reaction conditions.

Here, Carsten Bolm and colleagues have developed a base-assisted ball milling process for the degradation of lignin and wood.  The process is transition metal- and solvent-free and is tolerant of standard reagent impurities and water.  The authors hope that further work into optimising this reaction can reduce the current quantities of base required.

Read this article for free until the 3rd January!

Mechanochemical degradation of lignin and wood by solvent-free grinding in a reactive medium, Tillmann Kleine, Julien Buendia and Carsten Bolm, Green Chem., 2013, DOI: 10.1039/C2GC36456E

You may also be interested in this article too – free to access for 2 weeks:

Mechanocatalysis for biomass-derived chemicals and fuels, Sandra M. Hick, Carolin Griebel, David T. Restrepo, Joshua H. Truitt, Eric J. Buker, Caroline Bylda and Richard G. Blair, Green Chem., 2010, 12, 468-474

Stay up-to-date with the latest news and content in Green Chemistry by registering for our free table of contents alerts.