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Showing posts with label REACTIONS. Show all posts
Showing posts with label REACTIONS. Show all posts

Saturday 4 June 2016

Heterogeneous catalytic approaches in C-H activation reactions

Green Chem., 2016, Advance Article
DOI: 10.1039/C6GC00385K, Critical Review
Stefano Santoro, Sergei I. Kozhushkov, Lutz Ackermann, Luigi Vaccaro
This review summarizes the development of user-friendly, recyclable and easily separable heterogeneous catalysts for C-H activation during the last decade until December 2015.

http://pubs.rsc.org/en/Content/ArticleLanding/2016/GC/C6GC00385K?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FGC+%28RSC+-+Green+Chem.+latest+articles%29#!divAbstract

Despite the undisputed advances and progress in metal-catalyzed C–H functionalizations, this atom-economical approach had thus far largely been developed with the aid of various metal catalysts that were operative in a homogeneous fashion. 

While thereby major progress was accomplished, these catalytic systems featured notable disadvantages, such as low catalyst recyclability. This review summarizes the development of user-friendly, recyclable and easily separable heterogeneous catalysts for C–H activation.

This strategy was characterized by a remarkably broad substrate scope, considerable levels of chemo- and site-selectivities and proved applicable to C–C as well as C–heteroatom formation processes. 

Thus, recyclable catalysts were established for arylations, hydroarylations, alkenylations, acylations, nitrogenations, oxygenations, or halogenations, among others. The rapid recent progress in selective heterogeneous C–H functionalizations during the last decade until December 2015 is reviewed.


Heterogeneous catalytic approaches in C–H activation reactions

*
Corresponding authors
a
Laboratory of Green Synthetic Organic Chemistry, Dipartimento di Chimica Biologia e Biotecnologie, Università di Perugia, Via Elce di Sotto, 8 – 06123 Perugia, Italy 
E-mail: luigi.vaccaro@unipg.it
Web: http://www.dcbb.unipg.it/greensoc
b
Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstrasse 2, 37077 Göttingen, Germany 
E-mail: Lutz.Ackermann@chemie.uni-goettingen.de
Web: http://www.ackermann.chemie.uni-goettingen.de
Green Chem., 2016, Advance Article

DOI: 10.1039/C6GC00385K     




















Laboratory of Green Synthetic Organic Chemistry, Dipartimento di Chimica Biologia e Biotecnologie, Università di Perugia, Via Elce di Sotto, 8 – 06123 Perugia, Italy 
E-mail: luigi.vaccaro@unipg.it
Web: http://www.dcbb.unipg.it/greensoc

Extra clips
 C-H Activation :: Wiley-VCH Hot Topics






 
 The Yu Lab
www.scripps.edu
"Ligand-Enabled Triple C-H Activation Reactions: One-Pot Synthesis of Diverse 4-Aryl-2-quinolinones from Propionamides" Angew. Chem. Int. Ed. 2014, 53, ...

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Friday 20 September 2013

Molecular Storage Provides Chlorine and Phosgene Safely

Molecular Storage Provides Chlorine and Phosgene Safely

Photodecomposition of tetrachloroethylene provides a safer source of small chlorinated building blocks for organic synthesis

Wednesday 21 August 2013

Direct synthesis of hydrogen peroxide in water in a continuous trickle bed reactor optimized to maximize productivity



Hydrogen peroxide direct synthesis was studied in continuous mode over a 5% wt Pd/C commercial catalyst in a Trickle Bed Reactor. The target of the study was to maximize the hydrogen peroxide production. The catalyst was uniformly diluted in quartz sand at different concentrations to investigate their effects on the direct synthesis.
The amount of catalyst and the distribution of the catalyst along the bed were optimized to obtain the highest possible yield. The distribution of the catalyst along the bed gave the possibility to significantly improve the selectivity and production of hydrogen peroxide (up to 0.5% under selected conditions). Higher production rate and selectivity were found when the catalyst concentration was decreased along the bed from the top to the bottom as compared to the uniformly dispersed catalyst.
The H2/Pd ratio was found to be an important parameter that has to be investigated in the hydrogen peroxide direct synthesis. The effect of a pretreatment of the catalyst with a solution of sodium bromide and phosphoric acid was studied; the results showed how a catalyst pretreatment can lead to a real green hydrogen peroxide synthesis in water. Some optimization guidelines are also provided.
Green Chem., 2013, 15,2502-2513
DOI: 10.1039/C3GC40811F, Paper


*
Corresponding authors
a
Department of Chemical Engineering, Åbo Akademi University, Turku/Åbo, Finland
E-mail: bpierdom@abo.fi ;
Fax: +358 2 215 4479 ;
Tel: +358 2 215 4555
b
Department of Chemical Engineering and Environmental Technology, University of Valladolid, Valladolid, Spain
E-mail: jgserna@iq.uva.es
Hydrogen peroxide direct synthesis was studied in continuous mode over a 5% wt Pd/C commercial catalyst in a Trickle Bed Reactor.

Iodine-mediated arylation of benzoxazoles with aldehydes



A simple and efficient methodology for the arylation of benzoxazoles with aldehydes using iodine as the mediator has been developed. The reaction proceeded smoothly with a range of substrates to give the corresponding arylated products in moderate to good yields
Green Chem., 2013, 15,2365-2368
DOI: 10.1039/C3GC41027G, Communication


*
Corresponding authors
a
Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, The Nanos, Singapore 138669, Singapore
E-mail: ygzhang@ibn.a-star.edu.sg ;
Fax: (+65) 6478-9020
A simple and efficient methodology for the arylation of benzoxazoles with aldehydes using iodine as the mediator has been developed

Tuesday 23 July 2013

Nano-Technoloogy Makes Medicine Greener


The ultra small nanoreactors have walls made of lipids. During their fusion events volumes of one billionth of a billionth of a liter were transferred between nanoreactors allowing their cargos to mix and react chemically. We typically carried out a million of individual chemical reactions per cm2 in not more than a few minutes. (Credit: Image courtesy of University of Copenhagen)http://www.sciencedaily.com/releases/2011/11/111103132357.htm
 Researchers at the University of Copenhagen are behind the development of a new method that will make it possible to develop drugs faster and greener. Their work promises cheaper medicine for consumers.
Over the last 5 years the Bionano Group at the Nano-Science Center and the Department of Neuroscience and Pharmacology at the University of Copenhagen has been working hard to characterise and test how molecules react, combine together and form larger molecules, which can be used in the development of new medicine.http://www.sciencedaily.com/releases/2011/11/111103132357.htm



Tuesday 16 July 2013

A new labdane diterpene from Rauvolfia tetraphylla Linn. (Apocynaceae)

A new labdane diterpene from Rauvolfia tetraphylla Linn. (Apocynaceae)
A new labdane diterpene from Rauvolfia tetraphylla Linn. (Apocynaceae)

Rauvolfia tetraphylla Linn. (syn. R. canescens L., family: Apocynaceae) holds an important position in the Indian traditional system of medicine, and has other immense applications. This particular plant is regarded as a rich source of a wide variety of important alkaloid constituents such as reserpine, reserpiline, raujemidine, isoreserpiline, deserpidine, aricine, ajmaline, ajmalicine, yohimbines, serpentine, sarpagine, vellosimine and tetrphylline. However, there is no report on the terpenoid constituent from this plant, and we report the isolation from the air-dried stems and branches of R. tetraphylla and structural elucidation of a new labdane diterpene, 3-hydroxy-labda-8(17),13(14)-dien-12(15)-olide (1; Fig. 1) bearing  an unusual -lactone moiety.
Structure of labdane diterpene
Fig. 1 Structure of labdane diterpene
Goutam Brahmachari*, Lalan Ch. Mandal, Dilip Gorai, Avijit Mondal, Sajal Sarkar and Sasadhar Majhi
Doi: 10.3184/174751911X13220462651507

read all at

Thursday 4 July 2013

Catalyst duo exerts powerful stereocontrol

diastereomer
The dual catalyst enables selective access to the required stereoisomer © Science/AAAS

Chemists from the Swiss Federal Institute of Technology, ETH Zurich, have teamed chiral catalysts in pairs to selectively drive a reaction towards desired stereoisomeric products with high selectivity. Each catalyst activates one reagent and controls its substituent arrangement as it bonds to the other to form two neighbouring chiral centres. ‘We have shown that it is possible to develop fully stereodivergent reaction processes,’ says Erick Carreira, who led the work. ‘We expect that additional reactions displaying full stereodivergency will be identified.’

read all at
http://www.rsc.org/chemistryworld/2013/05/catalyst-duo-powerful-stereocontrol-diastereomer

References

S Krautwald et alScience, 2013, DOI: 10.1126/science.1237068

Monday 24 June 2013

Lab Reproduction of Marine Compound with Antibiotic Properties




 
Baringolin is a marine product with antibiotic properties. Image: IRB Barcelona
 

Barcelona, Spain (Scicasts) – Bacterial resistance to drugs leads pharmaceutical labs to be in constant search for new antibiotics to treat the same diseases. For the last thirty years, the sea bottom has yielded a wealth of substances with properties of interest to the pharmaceutical industry.
 
Isolated from a marine microorganism off the coast of Alicante by the company BioMar, baringolin shows promising antibiotic activity at a very low concentration. The Combinatorial Lab headed by Fernando Albericio at the Institute for Research in Biomedicine (IRB Barcelona), which collaborates with BioMar, has now synthesized this molecule and revealed its structure. Today's results open up the possibility to better understand how this substance works and to design derivatives to turn into a viable drug in the next 10 years. These findings are published in todays' online edition of the journal Angewandte Chemie.

read all at

http://scicasts.com/bioit/1858-drug-development/6186-lab-reproduction-of-marine-compound-with-antibiotic-properties

From left to right, this image shows researchers Mercedes Alvárez, Xavier Just-Baringo and Fernando Albericio from the IRB Barcelona.
(Photo Credit: IRB Barcelona)


/files/Image/XavierJust.jpg

Xavier Just, PhD student at IRB Barcelona, has reproduced the natural structure in the lab

 Reference article:
Total Synthesis and Stereochemical Assignment of Baringolin
Xavier Just-Baringo, Paolo Bruno, Lars K. Ottesen, Librada M. Cañedo, Fernando Albericio and Mercedes Álvarez.
Angewandte Chemie (2013) http://dx.doi.org/10.1002/ange.201302372 (German Edition) http://dx.doi.org/10.1002/anie.201302372 (International Edition)