Green Chemistry Blog

Scientists from Germany have developed an efficient diastereoselective synthesis of 2,5-disubstituted tetrahydrofurans in three steps.

Magnus Rueping and Vilas Phapale used [IrCl(cod)]2 to catalyze the α-alkylation of substituted acetophenones with solketal (obtained from the protection of glycerol by actenone) as the hydrogen donor.  This route avoids the use of electrophilic alkylating agents like alkyl halides and as a result does not suffer from drawbacks such as salt or by-product formation.  The resulting products could then undergo reduction with NaBH4 to give the corresponding secondary alcohols, before subsequent acetyl deprotection and cyclisation by FeCl3 to give 2,5-disubstituted tetrahydrofurans. 

Furthermore, a one-pot, three-step version of this procedure could be performed which does not require chomatographic purification of any of the intermediates.

This article is free to access until the 22nd November 2011!  To read more, please click the link below…

Effective synthesis of 2,5-disubstituted tetrahydrofurans from glycerol by catalytic alkylation of ketones, Magnus Rueping and Vilas B. Phapale, Green Chem., 2011, DOI: 10.1039/C1GC15764G

Lipases immobilized onto biogenous iron oxide via an organic bridging group were applied to the kinetic resolution of secondary alcohols and could be used up to 5 times.

Immobilization of enzymes helps to achieve cost-effective, clean biocatalysis.  However, the method of immobilization employed can have a big impact on the catalytic activity, selectivity, thermostability and recyclability of enzymes. 

Scientists from Japan have used biogenous iron oxide (BIO) from iron-oxidising bacteria as a support for enzymes.  BIO was chemically modified with silane coupling agents to allow immobilization of the enzyme.  The supported catalyst was then applied to the resolution of secondary alcohols and could achieve a turnover frequency of 33 000 h^-1.  Heat treatment of BIO before chemical modification generated magnetic-BIO which was also employed as a support, and the immobilized enzymes could be recovered easily by using a magnet.

This article is free to access until 22nd November!  Click the link below to read more…

Highly active lipase immobilized on biogenous iron oxide via an organic bridging group: the dramatic effect of the immobilization support on enzymatic function, Tadashi Ema, Yuki Miyazaki, Izumi Kozuki, Takashi Sakai, Hideki Hashimoto and Jun Takada, Green Chem., 2011, DOI: 10.1039/C1GC15877E

An new and innovative method of free enzyme recycling from a reaction mixture has been developed which relies only on the physical properties of the reaction medium.

Biotechnology is gaining an increasing role in industrial processes, but various factors including poor industrial availability of free enzymes and efficient recycling procedures limit utilization.  Common methods for enzyme recycling include immobilization of the enzyme onto a suitable support material or by encapsulation in aqueous gels.  However, disadvantages of these methods include leeching of enzymes and loss of activity.

Arno Behr and his team from the Technical University of Dortmund, Germany, have provided a new solution to the problem of enzyme recycling.  They used a mixture of three solvents (water, methanol and hexanol) which are immiscible at room temperature.  When heated to the reaction temperature, the solvents form one phase which allows the reaction to proceed with no mass-transfer limitations.  Cooling the mixture to below the critical solution temperature leads to a biphasic system, resulting in the product phase being simply separated from the phase containing the catalyst, which can then be reused.  The catalyst could be used again over 5 sequential runs with only a 2% loss in maximum yield.

This article is free to access until the 17th November 2011!  Click the link below to read more…

A liquid immobilisation concept for enzymes by thermomorphic solvent systems, Arno Behr, Leif Johnen and Bastian Daniel, Green Chem., 2011, DOI: 10.1039/C1GC15802C

Scientists from New Zealand have used food additive-derived ionic liquids for extracting wood lignin.

Wood cellulose, the most abundant biopolymer on earth, has great potential as a renewable feedstock, but in order to ‘unlock’ this potential, the various components of wood cellulose need to separated and processes individually.  The three main components are cellulose, hemicellulose and lignin.  However, current methods used to separate these components, for example Kraft pulping, have many draw backs such as high operating temperatures and pressures and many sequential steps. 

In this work, André Pinkert and his team used food additive-derived ionic liquids for seperating wood lignin and looked at the influence of selected parameters on the process.  In one gentle step, an extraction efficiency of e= 0.43 of wood lignin was achieved which increased to e= 0.60 in the presence of a co-solvent.  The gentle conditions employed here did not decrease the crystallinity of the wood sample, and resulted in lignin with both a larger molar mass and a more uniform molar mass distribution compared to commercially available Kraft lignin.

Click the links below to read more.  This article is free to access until the 18th November 2011!

Extracting wood lignin without dissolving or degrading cellulose: investigations on the use of food additive-derived ionic liquids, André Pinkert, Dagmar F. Goeke, Kenneth N. Marsh and Shusheng Pang, Green Chem., 2011, DOI: 10.1039/C1GC15671C

A strategy to utilize corncobs to generate porous carbonaceous materials has been reported by scientists from Spain and the Philippines, which were then used to generate biodiesel from waste oils.

There has been increased focus on reducing organic wastes in industry and for providing and utilizing renewable chemicals and fuels.  Waste valorisation is attracting considerable attention, providing an alternative to the disposal of a range of waste materials in landfill sites.  In particular, the valorisation of food wastes is considered to be very promising. 

In this work, researchers led by Rick Arneil Arancon and Rafael Luque utilized corncobs, which are a common food waste, and generated microporous carbonaceous material.  The material was then subsequently sulfonated to give a solid acid catalyst which exhibited excellent activity in the simultaneous esterification/transesterification of waste oils. 

This article is free to access until 1st November 2011!  To read more, please click on the link below:

Valorisation of corncob residues to functionalised porous carbonaceous materials for the simultaneous esterification/transesterification of waste oils, Rick Arneil Arancon, Higinio R. Barros Jr, Alina M. Balu, Carolina Vargas and Rafael Luque, Green Chem., 2011, DOI: 10.1039/C1GC15908A