Green Chemistry Blog

Chinese scientists have developed a new method for synthesising 2-arylsubstituted thiazolo[5,4-d]pyrimidine derivatives under mild conditions.

2-Arylsubstituted thiazolo[5,4-d]pyrimidine derivatives are the main motif in many pharmacologically relevant compounds including Tie-2 inhibitors and immunosuppressive agents.  Given the interest in these compounds, finding a mild and effective route to synthesis them is important.  Existing methods involve the use of toxic reagents and harsh conditions which limit their applications.  In this work, Tu-Yan Li, Li-Ping Sun and colleagues from China Pharmaceutical University, Nanjing, China, have developed a procedure for the direct arylation of thiazolo[5,4-d]pyrimidine derivatives with aryl iodides.  They employ a combination of Pd(Ph3)4 and Ag2CO3 used exclusively in water at 60 °C, giving the products in good to excellent yields.

This article is free to access until the 6th July 2012!  Click on the link below to find out more…

“On water” direct Pd-catalysed C–H arylation of thiazolo[5,4-d]pyrimidine derivatives, Ye-Xiang Su, Ya-Hui Deng, Ting-Ting Ma, Yu-Yan Li and Li-Ping Sun, Green Chem., 2012, DOI: 10.1039/C2GC35399G

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Efficient and convenient C-3 functionalization of indoles through Ce(OAc)₃/TBHP-mediated oxidative C–H bond activation in the presence of β-cyclodextrin, Yu Lin Hu, Hui Jiang and Ming Lu, Green Chem., 2011, 13, 3079-3087

Greener solvents for ruthenium and palladium-catalysed aromatic C–H bond functionalisation, Cedric Fischmeister and Henri Doucet, Green Chem., 2011, 13, 741-753

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Encaging the complex PdCl₂(py)₂ gave a highly efficient and reusable catalyst for the Suzuki-Miyaura cross-coupling reaction.

Tao Li and colleagues from Huazhong University of Science and Technology, China, successfully encaged the PdCl₂(py)₂ complex in the interior space of hollow silicate-1 spheres.  This new material was then applied to the Suzuki-Miyaura cross-coupling reaction of various aryl halides and arylboronic acids in aqueous media.  Even at Pd loadings of 0.0188 mol%, the catalyst gave fast conversions to the desired products under mild conditions.  Notably, due to the ‘anti-leaching’ effect of the zeolitic shell surrounding the Pd species, the catalyst showed excellent stability and reusability and could be reused 10 times without any appreciable loss of activity. 

This article is free to access until the 29th June 2012!  Click on the link below to find out more…

PdCl₂(py)₂encaged in monodispersed zeolitic hollow spheres: a highly efficient and reusable catalyst for Suzuki–Miyaura cross-coupling reaction in aqueous media, Zhenhong Guan, Jianglin Hu, Yanlong Gu, Haojun Zhang, Guangxing Li and Tao Li, Green Chem., 2012, DOI: 10.1039/C2GC35302D

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Heterogeneous catalytic synthesis using microreactor technology, Christopher G. Frost and Lynsey Mutton, Green Chem., 2010, 12, 1687-1703

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Several mesoporous substituted silicates were applied to the acetalization of acetone with glycerol to yield solketal.

The team of scientists led by Pablo Pescarmona from KU Leuven, Belgium, illustrate for the first time that mesoporous Lewis acid catalysts can be active for this reaction to produce solketal.  Solketal is a very valuable compound with direct applications as a fuel additive, surfactant and flavouring agent.  Of the catalysts tested, the catalyst which showed the highest conversion and turnover numbers was the novel Hf-TUD-1 material.  Along with two other materials, these catalysts gave superior results compared to a reference solid acid catalyst such as Ultrastable zeolite Y.  The active materials do not suffer from leaching and could be efficiently reused in consecutive catalytic cycles.

This article is free to access until the 12th June 2012!  Click on this link below to find out more…

Highly-efficient conversion of glycerol to solketal over heterogeneous Lewis acid catalysts, Li Li, Tamás I. Korányi, Bert F. Sels and Paolo P. Pescarmona, Green Chem., 2012, DOI: 10.1039/C2GC16619D

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Selective conversion of trioses to lactates over Lewis acid heterogeneous catalysts, Li Li,  Christophe Stroobants, Kaifeng LinPierre A. Jacobs, Bert F. Sels and Paolo P. Pescarmona, Green Chem., 2011, 13, 1175-1181

Zeolite-catalysed conversion of C₃ sugars to alkyl lactates, Paolo P. Pescarmona, Kris P. F. Janssen, Chloë Delaet, Christophe Stroobants, Kristof Houthoofd, An Philippaerts, Chantal De Jonghe, Johan S. Paul, Pierre A. Jacobs and Bert F. Sels, Green Chem., 2010, 12, 1083-1089

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Scientists from Belgium have developed an environmentally friendly route to separate cobalt from nickel, magnesium and calcium in chloride medium.

Koen Binnemans and colleagues from KU Leuven and Umicore, Belgium used undiluted phosphonium-based ionic liquids as the extractants with tri(hexyl)tetradecylphosphonium chloride (Cyphos IL 101) as the best ionic liquid tested in terms of commercial availability, separation characteristics and ease of handling.  The main advantage of their method is the fact that no organic diluents are required and thus volatile organic solvents can be avoided. The process enabled separation factors greater than 50 000 to be observed for cobalt/nickel separation.  In addition, the ionic liquid can easily be recovered and reused as extractant so there is potential for a continuous extraction process to be developed.

This article is free to access until the 6th June 2012!  Click on the link below to find out more…

An environmentally friendlier approach to hydrometallurgy: highly selective separation of cobalt from nickel by solvent extraction with undiluted phosphonium ionic liquids, Sil Wellens, Ben Thijs and Koen Binnemans, Green Chem., 2012, DOI: 10.1039/C2GC35246J

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Processing of metals and metal oxides using ionic liquids, Andrew P. Abbott, Gero Frisch, Jennifer Hartley and Karl S. Ryder, Green Chem., 2011, 13, 471-481

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A supported organaocatalyst has been developed for direct asymmetric Aldol reaction in water with higher enantioselectivity than the original homogeneous catalyst.

Asymmetric organocatalyst is considered to be a very powerful tool for stereoselective synthesis on enantiomerically enriched compounds.  However, organocatalytic reactions, whilst avoiding many of the problems associated with metal catalysts, often require high catalyst loadings and tedious purification of the products. 

In this work, Roser Pleixats and colleagues from the Autonomous University of Barcelona, the University of Alicante (Spain) and the Institute Charles Gerhardt Montpellier (France), have developed a recyclable silica-supported prolinamide organocatalyst.  The catalyst was applied to the direct asymmetric Aldol reaction, and allowed reactions to be conducted exclusively in water without the need of a co-catalyst.  This also resulted in easier isolation of the product and good recycling (at least three times) of the catalyst without the need for regeneration. 

This article is free to access until the 24th May 2012!  Click on the link below to find out more…

Recyclable silica-supported prolinamide organocatalysts for direct asymmetric Aldol reaction in water, Amàlia Monge-Marcet, Xavier Cattoën, Diego A. Alonso, Carmen Nájera, Michel Wong Chi Man and Roser Pleixats, Green Chem., 2012, DOI: 10.1039/C2GC35227C

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Advances in catalytic metal-free reductions: from bio-inspired concepts to applications in the organocatalytic synthesis of pharmaceuticals and natural products, Magnus Rueping, Jeremy Dufour and Fenja R. Schoepke, Green Chem., 2011, 13, 1084-1105

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