Wednesday, 21 August 2013

Organocatalytic 1,3-dipolar cycloaddition reactions of ketones and azides with water as a solvent


Green Chem., 2013, 15,2384-2388
DOI: 10.1039/C3GC41126E, Communication

Corresponding authors
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore
E-mail: ;
Fax: (+)65-6516-1691
HuBei Collaborative Innovation Center of Non-power Nuclear Technology, Hubei University of Science and Technology, Hubei Province, China

Received 12 Jun 2013, Accepted 19 Jul 2013
First published online 22 Jul 2013
We reported an enamine catalyzed strategy to fully promote a 1,3-dipolar cycloaddition to access a vast pool of substituted 1,2,3-triazoles in water.

Graphene oxide as a facile acid catalyst for the one-pot conversion of carbohydrates into 5-ethoxymethylfurfural

Graphene oxide obtained by the Hummers method was discovered to be an efficient and recyclable acid catalyst for the conversion of fructose-based biopolymers into 5-ethoxymethylfurfural (EMF). EMF yields of 92%, 71%, 34% and 66% were achieved when 5-hydroxymethylfurfural (HMF), fructose, sucrose and inulin were used as starting materials, respectively.

Green Chem., 2013, 15,2379-2383
DOI: 10.1039/C3GC41109E, Communication

Corresponding authors
Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, PR China
E-mail: ;
Fax: (+86) 351-4041153
University of Chinese Academy of Sciences, Beijing, PR China
State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, PR China
Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, P. R. China
Graphene oxide was used as a facile carbon catalyst for converting renewable carbon sources into the potential biofuel 5-ethoxymethylfurfural.

Monday, 19 August 2013


The Prins reaction is an organic reaction consisting of an electrophilic addition of an aldehyde or ketone to an alkene or alkyne followed by capture of a nucleophile.[1][2][3] The outcome of the reaction depends on reaction conditions (scheme 1). With water and a protic acid such as sulfuric acid as the reaction medium and formaldehyde the reaction product is a 1,3-diol. When water is absent, the cationic intermediate loses a proton to give an allylic alcohol. With an excess of formaldehyde and a low reaction temperature the reaction product is a dioxane. When water is replaced by acetic acid the corresponding esters are formed.


The original reactants employed by Dutch chemist Hendrik Jacobus Prins in his 1919 publication were styrene (scheme 2), pinene, camphene, eugenol, isosafrole and anethole.
Scheme 2. The Prins reaction with styrene
In 1937 the reaction was investigated as part of a quest for di-olefins to be used in synthetic rubber.
Scheme 3. Isoprene Prins reaction

Reaction mechanism

The reaction mechanism for this reaction is depicted in scheme 5. The carbonyl reactant (2) is protonated by a protic acid and for the resulting oxonium ion 3 two resonance structures can be drawn. This electrophile engages in an electrophilic addition with the alkene to the carbocationic intermediate 4. Exactly how much positive charge is present on the secondary carbon atom in this intermediate should be determined for each reaction set. Evidence exists for neighbouring group participation of the hydroxyl oxygen or its neighboring carbon atom. When the overall reaction has a high degree of concertedness, the charge built-up will be modest.
Scheme 5. Prins reaction mechanism
The three reaction modes open to this oxo-carbenium intermediate are:
  • in blue: capture of the carbocation by water or any suitable nucleophile through 5 to the 1,3-adduct 6.
  • in black: proton abstraction in an elimination reaction to unsaturated compound 7. When the alkene carries a methylene group, elimination and addition can be concerted with transfer of an allyl proton to the carbonyl group which in effect is an ene reaction in scheme 6.
Scheme 6. Carbonyl-ene reaction versus Prins reaction
  • in green: capture of the carbocation by additional carbonyl reactant. In this mode the positive charge is dispersed over oxygen and carbon in the resonance structures 8a and 8b. Ring closure leads through intermediate 9 to the dioxane 10. An example is the conversion of styrene to 4-phenyl-m-dioxane.[4]
  • in gray: only in specific reactions and when the carbocation is very stable the reaction takes a shortcut to the oxetane 12. The photochemical Paternò–Büchi reaction between alkenes and aldehydes to oxetanes is more straightforward.


Many variations of the Prins reaction exist because it lends itself easily to cyclization reactions and because it is possible to capture the oxo-carbenium ion with a large array of nucleophiles. The halo-Prins reaction is one such modification with replacement of protic acids and water by lewis acids such as stannic chloride and boron tribromide. The halogen is now the nucleophile recombining with the carbocation. The cyclization of certain allyl pulegones in scheme 7 with titanium tetrachloride in dichloromethane at −78 °C gives access to the decalin skeleton with the hydroxyl group and chlorine group predominantly in cis configuration (91% cis).[5] This observed cis diastereoselectivity is due to the intermediate formation of a trichlorotitanium alkoxide making possible an easy delivery of chlorine to the carbocation ion from the same face. The trans isomer is preferred (98% cis) when the switch is made to a tin tetrachloride reaction at room temperature.
Scheme 7. Halo-Prins reaction
The Prins-pinacol reaction is a cascade reaction of a Prins reaction and a pinacol rearrangement. The carbonyl group in the reactant in scheme 8[6] is masked as a dimethyl acetal and the hydroxyl group is masked as a triisopropylsilyl ether (TIPS). With lewis acid stannic chloride the oxonium ion is activated and the pinacol rearrangement of the resulting Prins intermediate results in ring contraction and referral of the positive charge to the TIPS ether which eventually forms an aldehyde group in the final product as a mixture of cis and trans isomers with modest diastereoselectivity.

Scheme 8. Halo-Prins reaction


The Prins reaction is used in total synthesis of complex natural products, for example, in a key step of that of the synthesis of exiguolide:[7]

Prins reaction Kwon 2008

External links


  1. ^ Condensation of formaldehyde with some unsaturated compounds H. J. Prins, Chemisch Weekblad, 16, 64, 1072, 1510 1919
  2. ^ Chemical Abstracts 13, 3155 1919
  3. ^ The Olefin-Aldehyde Condensation. The Prins Reaction. E. Arundale, L. A. Mikeska Chem. Rev.; 1952; 51(3); 505–555. Link
  4. ^ 4-Phenyl-m-dioxane R. L. Shriner and Philip R. Ruby Organic Syntheses, Coll. Vol. 4, p.786 (1963); Vol. 33, p.72 (1953). Article
  5. ^ Syn- and Anti-Selective Prins Cyclizations of ,-Unsaturated Ketones to 1,3-Halohydrins with Lewis Acids R. Brandon Miles, Chad E. Davis, and Robert M. Coates J. Org. Chem.; 2006; 71(4) pp 1493 – 1501; Abstract
  6. ^ Scope and Facial Selectivity of the Prins-Pinacol Synthesis of Attached Rings Larry E. Overman and Emile J. Velthuisen J. Org. Chem.; 2006; 71(4) pp 1581 – 1587; Abstract
  7. ^ Total Synthesis of (+)-Exiguolide Min Sang Kwon, Sang Kook Woo, Seong Wook Na, and Eun Lee Angew. Chem. Int. Ed. 2008, 47, 1733–1735 doi:10.1002/anie.200705018

واکنش پرینز

واکنش پرینز
واکنش پرینز (prins) یک واکنش آلی شامل افزایش الکتروفیلی یک آلدهید یا کتون به یک آلکن یا آلکین با گرفتن نوکلئوفیل است. نتیجه واکنش بستگی به شرایط واکنش دارد (طرح 1).در حضور آب و اسید پروتیک مانند سولفوریک اسید به صورت واسطه واکنش و فرمالدهید محصول واکنش یک 3و1- دی ال 3 است.زمانی که آب حضور ندارد آب زدایی برای تشکیل یک الکل آلیلی 4 اتفاق می افتد. با مقدار اضافی از فرمالدهید و دمای کم واکنش محصول واکنش یک دی اکسان 5 است. زمانی که 

آب به وسیله استیک اسید جایگزین می شود استرهای مربوطه تشکیل می شود.

Friday, 2 August 2013

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

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.


DNA: From Structure to Synthesis


Vol. 35 No. 2
March-April 2013

DNA: From Structure to Synthesis
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.

Novel Aromatic Compounds

Novel Aromatic Compounds

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).


Andrew Holmes to Give Nozoe Lecture

Andrew Holmes, University of Melbourne, Australia, will be the Nozoe Lecturer in Taipei next year
Read more

Hybrid Nanoscale Ligand

A new salen–C60 dyad forms complexes with transition metals, thereby tuning the optical, redox, and catalytic properties
Read more

sp3-Carbon-Based Liquid Crystals

The liquid-crystalline phase of poly(ethylidene acetate) is described and explained by the formation of triple-helix aggregates
Read more

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
Read more