The Structure Makes the Poison

The orientation of the tert-butyl group determines the toxicity of the potent antillatoxin

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Deep Fried Fish and Furan

The toxic accumulation of furan in breaded fish products can be reduced by adjusting the cooking conditions

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From the Wings of Butterflies: The Discovery and Synthesis of Alimta

Vol. 33 No. 5
September-October 2011

From the Wings of Butterflies: The Discovery and Synthesis of Alimta

http://www.iupac.org/publications/ci/2011/3305/1_taylor.html

by Edward C. Taylor

The following essay describes in broad terms the history of the discovery of Alimta. It was written as a part of a brochure celebrating the dedication of Princeton’s magnificent new chemistry building, completed by the end of 2010. The building, recognized as perhaps the finest, best-equipped, and designed facility for academic chemistry research in the country, was financed by royalties to Princeton from sales of Alimta by Eli Lilly & Co., to whom Princeton had given an exclusive license. The article was addressed to a general audience; my lecture in Glasgow1 filled in the organic and heterocyclic chemistry involved in the extensive explorations that finally led to the discovery and synthesis of Alimta.

http://www.iupac.org/publications/ci/2011/3305/1_taylor.html





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DNA: From Structure to Synthesis

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Vol. 35 No. 2
March-April 2013

DNA: From Structure to Synthesis

by Krishna N. Ganesh
 http://www.iupac.org/publications/ci/2013/3502/2_caruthers.html

The DNA double helix made up of two antiparallel strands complementary to each other through specific base pairing of A with T and G with C codes the key information necessary for synthesis and regulation of all proteins and enzymes required of functioning of a cell from cell division to cell differentiation and cell development. The discovery also gave birth to the fields of molecular and structural biology, which have been key to the genetic revolution that has resulted in the development of vital products, ranging from hormones and enzymes to therapeutic molecules and vaccines. The penultimate achievement stemming from the discovery of DNA’s structure was the unraveling of the entire human genome in 2001 and work continues unabated on the genomes of other organisms. These discoveries have implications for our understanding of diseases at the molecular level and, thereby, the development of cures. Some of the most spectacular applications take advantage of the self-assembling properties of the genetic molecule DNA to make nonbiological novel generic materials.http://www.iupac.org/publications/ci/2013/3502/2_caruthers.html

Novel Aromatic Compounds

Novel Aromatic Compounds

by Shih-Yuan Liu and Michael Haley
The 14th International Symposium on Novel Aromatic Compounds (ISNA-14) was held 24–29 July 2011 in Eugene, Oregon, USA, on the campus of the University of Oregon. Over 250 participants from 21 countries were present, making this gathering the largest ISNA conference on North American soil. The scientific program consisted of the 2011 Nozoe Lecture presented by Peter Bäuerle (University of Ulm, Germany), 11 plenary lectures, 20 invited lectures, 29 contributed lectures, and 160 posters presented in two sessions. This IUPAC-sponsored symposium was organized by Michael M. Haley (University of Oregon) and Benjamin T. King (University of Nevada, Reno, USA).

http://www.iupac.org/publications/ci/2011/3306/cc1_240711.html



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Andrew Holmes to Give Nozoe Lecture

Andrew Holmes, University of Melbourne, Australia, will be the Nozoe Lecturer in Taipei next year
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Hybrid Nanoscale Ligand

A new salen–C₆₀ dyad forms complexes with transition metals, thereby tuning the optical, redox, and catalytic properties
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sp3-Carbon-Based Liquid Crystals

The liquid-crystalline phase of poly(ethylidene acetate) is described and explained by the formation of triple-helix aggregates
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Bond-Length Alternation in Overcrowded Borazines

X-ray crystallography and state-of-the art computations were applied to the question of bond-length alternation in overcrowded borazines
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Co-Catalyzed Radical Cycloaddition of [60]Fullerene with Active Dibromides: Selective Synthesis of Carbocycle-Fused Fullerene Monoadducts

Co-Catalyzed Radical Cycloaddition of [60]Fullerene with Active Dibromides: Selective Synthesis of Carbocycle-Fused Fullerene Monoadducts

Shirong Lu, Weili Si, Ming Bao, Yoshinori Yamamoto, and Tienan Jin

WPI-Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577, Japan, and State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China

Org. Lett., Article ASAP

Publication Date (Web): July 23, 2013 (Letter)

DOI: 10.1021/ol401876n

http://pubs.acs.org/doi/abs/10.1021/ol401876n

An efficient and highly selective Co-catalyzed radical cycloaddition of [60]fullerene with active dibromides for the synthesis of three-, five-, six-, and seven-membered carbocycle-fused fullerene monoadducts has been reported. The controlled experiments unambiguously disclosed that the reaction proceeds through the formation of a fullerene monoradical as a key intermediate.

Co-Catalyzed Radical Cycloaddition of [60]Fullerene with Active Dibromides: Selective Synthesis of Carbocycle-Fused Fullerene Monoadducts

Co-Catalyzed Radical Cycloaddition of [60]Fullerene with Active Dibromides: Selective Synthesis of Carbocycle-Fused Fullerene Monoadducts

Shirong Lu, Weili Si, Ming Bao, Yoshinori Yamamoto, and Tienan Jin

WPI-Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577, Japan, and State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China

Org. Lett., Article ASAP

Publication Date (Web): July 23, 2013 (Letter)

DOI: 10.1021/ol401876n

http://pubs.acs.org/doi/abs/10.1021/ol401876n

An efficient and highly selective Co-catalyzed radical cycloaddition of [60]fullerene with active dibromides for the synthesis of three-, five-, six-, and seven-membered carbocycle-fused fullerene monoadducts has been reported. The controlled experiments unambiguously disclosed that the reaction proceeds through the formation of a fullerene monoradical as a key intermediate.

Anthony crasto presents ladderanes

WAIT FOR SLIDESHARE TO LOAD.............

Anthony crasto ladderanes from ANTHONY MELVIN CRASTO Ph.D

Redox-Switchable Catalyst for Ring-Closing Metathesis

 

Homogeneous, redox-switchable, N-heterocyclic carbene/ferrocenyl-based catalysts for ring-closing metathesis reactions
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Migration of Nanoparticles from Textiles

 

More realistic exposure scenario for wearing Ag- and TiO₂-engineered nanoparticle-containing textiles
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Self-Assembled Wheels

Self-Assembled Wheels

Two different terpyridine ligands self-assemble when mixed with zinc(II) ions to form 2D or 3D spoked wheels
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Titanium Dioxide for Sensitive Immunosensors

 

Titanium dioxide nanolayers as electrodes and titanium dioxide nanoparticles for enhanced immunosensing using electrochemiluminescence
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Fries Rearrangement Mechanism

The Fries rearrangement proceeds through ionic intermediates. The reaction depends on the structure of the substrates and the reaction conditions. 

The scheme depicts the formation of an ortho-acylated phenol from a substituted phenolic ester in the presence of aluminium trihalide catalyst. The photo Fries rearrangement mechanism proceeds through Radical intermediates.




The Fries rearrangement, named for the German chemist Karl Theophil Fries, is a rearrangement reaction of a phenyl ester to a hydroxy aryl ketone by catalysis of Lewis acids.^[1][2][3][4]
It involves migration of an acyl group of phenyl ester to benzene ring. The reaction is ortho and para selective and one of the two products can be favoured by changing reaction conditions, such as temperature and solvent.

Mechanism

Despite many efforts a definitive reaction mechanism for the Fries rearrangement is not available. Evidence for inter- and intramolecular mechanisms have been obtained by so-called cross-experiments with mixed reactants. Reaction progress is not dependent on solvent or substrate. A widely accepted mechanism involves a carbocation intermediate.

In the first reaction step a Lewis acid for instance aluminium chloride AlCl
3 co-ordinates to the carbonyl oxygen atom of the acyl group. This oxygen atom is more electron rich than the phenolic oxygen atom and is the preferred Lewis base. This interaction polarizes the bond between the acyl residue and the phenolic oxygen atom and the aluminium chloride group rearranges to the phenolic oxygen atom. This generates a free acylium carbocation which reacts in a classical electrophilic aromatic substitution with the aromatic ring. The abstracted proton is released as hydrochloric acid where the chlorine is derived from aluminium chloride. The orientation of the substitution reaction is temperature dependent. A low reaction temperature favors para substitution and with high temperatures the ortho product prevails. Formation of the ortho product is also favoured in non-polar solvents; as the solvent polarity increases, the ratio of the para product also increases.^[5]

Scope

Phenols react to esters but do not react to hydroxyarylketones with acylhalogen compounds under Friedel-Crafts acylation reaction conditions and therefore this reaction is of industrial importance for the synthesis of hydroxyarylketones which are important intermediates for several pharmaceutics such as paracetamol and salbutamol. As an alternative to aluminium chloride, other Lewis acids such as boron trifluoride and bismuth triflate or strong protic acids such as hydrogen fluoride and methanesulfonic acid can also be used. In order to avoid the use of these corrosive and environmentally unfriendly catalysts altogether research into alternative heterogeneous catalysts is actively pursued.

Limits

In all instances only esters can be used with stable acyl components that can withstand the harsh conditions of the Fries rearrangement. If the aromatic or the acyl component is heavily substituted then the chemical yield will drop due to steric constraints. Deactivating meta-directing groups on the benzene group will also have an adverse effect as can be expected for a Friedel–Crafts acylation.

Photo-Fries rearrangement

In addition to the ordinary thermal phenyl ester reaction a so-called photochemical Photo-Fries rearrangement exists^[6] that involves a radical reaction mechanism. This reaction is also possible with deactivating substituents on the aromatic group. Because the yields are low this procedure is not used in commercial production. However, photo-Fries rearrangement may occur naturally, for example when a plastic bottle made of polyethylene terephthalate (PET) is exposed to the sun, particular to UV light at a wavelength of about 310 nm, if the plastic has been heated to 40 degrees Celsius or above (as might occur in a car with windows closed on a hot summer day). In this case, photolysis of the ester groups would lead to leaching of phthalate from the plastic.^[7]

Anionic Fries rearrangment

In addition to Lewis acid and photo-catalysed Fries rearrangements, there also exists an anionic Fries rearrangement. In this reaction, the aryl ester undergoes ortho-metallation with a strong base, which then rearranges in a nucleophilic attack mechanism.

1.  Fries, K. ; Finck, G. (1908). "Über Homologe des Cumaranons und ihre Abkömmlinge". Chemische Berichte 41 (3): 4271–4284. doi:10.1002/cber.190804103146.
2.  Fries, K.; Pfaffendorf, W. (1910). "Über ein Kondensationsprodukt des Cumaranons und seine Umwandlung in Oxindirubin". Chemische Berichte 43 (1): 212–219. doi:10.1002/cber.19100430131.
3.  March, J. Advanced Organic Chemistry, 3rd Ed.; John Wiley & Sons: Chichester, 1985; S. 499ff.
4.  Blatt, A. H. Org. React. 1942, 1.
5.  Kürti, László; Czakó, Barbara (2005). Strategic Applications of Named Reactions in Organic Synthesis: Background and Detailed Mechanisms. Elsevier Academic Press. p. 181. ISBN 0123694833.
6.  Bellus, D. Advances in Photochemistry; John Wiley & Sons: Chichester, 1971; Vol. 8, 109–159.
7.  Norma Searle, "Environmental effects on polymeric materials," pp. 313–358, in Plastics and the Environment, edited by Anthony Andrade, Wiley, 2003.