Green Chemistry Blog

 Polyamides have been decomposed to ω-hydroxyalkanoic acid derivatives – important intermediates in the chemical industry – using supercritical methanol.  This is one of the first methods for economical upgrading of polymers through the depolymerisation process.

Akio Kamimura and colleagues from Yamaguchi University and UIbe Industries Ltd., Japan, have developed a method to convert polyamides to valuable chemicals.  Currently, recycling of plastics commonly involves converting the polymers back to their monomers. However, these methods are not always economically viable because they are often more expensive than other ways of treating waste plastics.  By converting polymers to valuable chemicals, this would make polymer recycling a more attractive route and solve some of the economic problems. 

In this study, by using supercritical methanol, Kamimura converted nylon-6 selectively to two valuable compounds – methyl 6-hydroxycapronate and methyl 5-hexenoate. Given that the average price for these ω-hydroxyalkanoic acid derivatives is about 6-7 times higher (per kg, based on 2008 figures) than the monomer (caprolactam), Kamimura believes that this method will open up new avenues in the development of plastics recycling.

To read more, please click the link below!  Full text Free until 20th July.

Direct conversion of polyamides to ω-hydroxyalkanoic acid derivatives by using supercritical MeOH, Akio Kamimura, Kouji Kaiso, Shuzo Suzuki, Yusuke Oishi, Yuki Ohara, Tsunemi Sugimoto, Kohichi Kashiwagi and Makoto Yoshimoto, Green Chem., 2011, DOI: 10.1039/C1GC15172J

A new method has been developed to synthesis spiro-substituted benzo[b]furo[3,4-e][1,4]diazepene derivatives in one step, forming two spiro rings and five σ bonds in the process.

This chemo- and regioselective [4+2+1] domino cyclization reaction was discovered by scientists from Xuzhou Normal University, China and Texas Tech University, USA.  The synthesis of  heterocyclic compounds with quaternary carbon centres is important as these compounds are useful intermediates in organic synthesis and are often biologically active. 

The procedure developed here is performed in water with microwave irradiation and uses easily available and cheap starting materials.  This one-pot reaction can be performed in 10-18 minutes with reduced waste production and without the use of any strong acids or metal promoters.  In addition, recrystallization and chromatography purification procedures can be avoided as the pure products can be obtained by simply washing the crude product with 95% ethanol.

The authors feel this will serve as a nice addition to Group-Assistant Purification chemistry.

Click the link below to read more! Full text free until 18th July.

[4+2+1] Domino cyclization in water for chemo- and regioselective synthesis of spiro-substituted benzo[b]furo[3,4-e][1,4]diazepine derivatives, Chuang Cheng, Bo Jiang, Shu-Jiang Tu and Guigen Li, Green Chem., 2011, DOI: 10.1039/C1GC15183E

An efficient method for the NMR analysis of chiral alcohols and amines has been developed with an improved detection limit. Valentine Ananikov and Nikolay Orlov, Zelinsky Institute of Organic Chemistry, Russia, prepared samples for analysis directly in the NMR tubes; this has big advantages over existing methods to analyse these compounds. 

NMR analysis of chiral compounds normally involves derivatisation with a suitable chiral agent to allow you to tell apart diastereoisomers in NMR spectra. The major limitation of this has been the fact that the derivatisation has to be done as a seperate reaction. This adds further work-up and purification procedures (generating waste), is time-consuming and means a relatively large sample is required for analysis.

However, Ananikov derivatised samples within the NMR tube, avoiding waste generation and providing samples for analysis in less than 5 min (including preparation time).  All analysis could be performed on a routine NMR instrument, and could give accurate measurements for samples less than 0.01 mg. This underlines the environmentally benign and superior nature of the procedure developed by this group.

To read more, please see:

NMR analysis of chiral alcohols and amines: development of an environmentally benign “in tube” procedure with high efficiency and improved detection limit, Nikolay V. Orlov and Valentine P. Ananikov, Green Chem., 2011, DOI: 10.1039/C1GC15191F

A polyoxometalate (POM)-ionic liquid hybrid has been shown to be an efficient hereogeneous catalyst for the epoxidation of alkenes with hydrogen peroxide.

Scientists from China led by Jun Wang from Nanjing University of Technology, synthesied a hybrid material by anion-exchanging a amino-functionalised ionic liquid cation with Keggin POM-anions.  These hybrid nanospheres were then applied to the epoxidation of alkenes with hydrogen peroxide.  Previous methods using POM catalysts in this reaction have often suffered from slow reaction rates, complex catalyst preparation and leaching of the active species into solution. 

 However, the POM-based ionic hybrid reported by Wang and co-workers, as well as being simple to produce, is an efficient heterogeneous catalyst exhibiting high conversion and selectivity.  In addition it can by recycled several times (after simple filtration) without any observable loss in conversion or selectivity.  Wang hopes that this new strategy may be extended to more versatile POM-based ionic hybrid catalysts for hydrogen peroxide, heterogeneous-based reactions.

To find out more, please see the full article, free until June 30th:

Polyoxometalate-based amino-functionalized ionic solid catalysts lead to highly efficient heterogeneous epoxidation of alkenes with H₂O₂, Yan Leng, Jun Wang, Dunru Zhu, Mingjue Zhang, Pingping Zhao, Zhouyang Long and Jun Huang, Green Chem., 2011, DOI: 10.1039/C1GC15302A