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Khand-Type Reaction (khand-type + reaction)

Distribution by Scientific Domains
Chemistry100%
Distribution within Chemistry
General & Introductory Chemistry44%

Selected Abstracts

Kinetic Resolutions by Enantioselective Pauson,Khand-Type Reaction

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009
Dong Eun Kim
Abstract A kinetic resolution of 1-arylallyl propargyl ethers by enantioselective Pauson,Khand-type reaction catalysts was successfully carried out. While cationic rhodium(I) with a BINAP-based ligand having an electron-deficient phosphine is the choice for the slow reacting substrates, neutral iridium(I) with a BINAP-based ligand possessing an electron-rich phosphine provided excellent results for the more reactive substrates. [source]

Rhodium-Catalyzed Pauson,Khand-Type Reaction Using Alcohol as a Source of Carbon Monoxide,

ANGEWANDTE CHEMIE, Issue 30 2010
Hoon Park
Drei mechanistisch unterschiedliche Reaktionen werden bei der neuartigen katalytischen intramolekularen Auto-Tandem-Synthese bicyclischer Cyclopentenone aus Eninen in Alkohol in Gegenwart eines Rhodiumkatalysators kombiniert: eine Alkoholoxidation, eine Aldehyddecarbonylierung und eine carbonylierende [2+2+1]-Cycloaddition (siehe Schema; dppp=Propan-l,3-diylbis(diphenylphosphan)). [source]

Rhodium-Catalyzed Intramolecular Alkyne-carbodiimide Pauson,Khand-Type Reaction.

CHEMINFORM, Issue 33 2007
Takao Saito
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

Catalytic Pauson,Khand-Type Reaction Using Aldehydes as a CO Source.

CHEMINFORM, Issue 38 2002
Takanori Shibata
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Rhodium-Catalyzed Asymmetric Aqueous Pauson,Khand-Type Reaction

CHEMISTRY - A EUROPEAN JOURNAL, Issue 13 2005
Fuk Yee Kwong Dr.
Abstract An interesting rhodium-catalyzed asymmetric aqueous Pauson,Khand-type reaction was developed. A chiral atropisomeric dipyridyldiphosphane ligand was found to be highly effective in this system. This operationally simple protocol allows both catalyst and reactants to be handled under air without precautions. Various enynes were transformed to the corresponding bicyclic cyclopentenones in good yield and enantiomeric excess (up to 95,% ee). A study of the electronic effects of the enyne substrates revealed a correlation between the electronic properties of the substrates and the ee value obtained in the product of the Pauson,Khand-type reaction. A linear free-energy relationship was observed from a Hammett study. [source]

2,2,-Bis[bis(3,5-di- tert -butyl-4-methoxyphenyl)phosphino]-6,6,-dimethoxy-1,1,-biphenyl in Intramolecular Rhodium(I)-Catalyzed Asymmetric Pauson,Khand-Type Reactions

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010
Dong Eun Kim
Abstract A cationic rhodium(I)/2,2,-bis[bis(3,5-di- tert -butyl-4-methoxyphenyl)phosphino]-6,6,-dimethoxy-1,1,-biphenyl (DTBM-MeO-BIPHEP) catalyst was highly efficient for the asymmetric catalytic Pauson,Khand reaction, especially for those substrates containing aryl group-substituted alkynes. The formation of the products that were derived from a ,-hydride eliminated intermediate 5 was completely suppressed over a wide range of substrates. This reaction was a serious process competing reaction with the migratory CO insertion that led to the Pauson,Khand reaction product and often substantially ruined the chemical yield of the Pauson,Khand reaction. The advantages of this system were clearly demonstrated for previously troublesome substrates, N -tosyl- (1b) and malonate-tethered 1,6-enynes (1c), that exhibited a higher enantioselectivity without a loss in the chemical yields. The obvious beneficial effects were attributed to the synergic effect of various factors, such as the electron density of the phosphorus of the ligand, the dihedral angles of the atropisomeric ligand, and the substitution on the phosphine aryl rings which play a crucial role in the stereochemical outcome of Rh-catalyzed Pauson,Khand reaction. [source]

Ruthenium-catalyzed carbonylative cycloaddition reactions involving carbonyl and imino groups as assembling units

THE CHEMICAL RECORD, Issue 4 2008
Naoto Chatani
Abstract This paper describes carbonylative cycloaddition reactions catalyzed by Ru3(CO)12. Ru3(CO)12 was found to catalyze an intramolecular Pauson,Khand-type reaction. Carbonylative cycloaddition reactions involving a carbonyl group in aldehydes, ketones, and esters as a two-atom assembling unit were also achieved in the presence of Ru3(CO)12 as the catalyst. The reaction of 5-hexyn-1-al and 6-heptyn-1-al derivatives with CO in the presence of Ru3(CO)12 resulted in cyclocarbonylation from which bicyclic ,, ,-unsaturated lactones were obtained. Intermolecular [2,+,2,+,1] carbonylative cycloaddition of alkenes, ketones, and CO was also catalyzed by Ru3(CO)12 as the catalyst to give saturated ,-lactone derivatives. Simple ketones were not applicable, but ketones having a CO or CN group at the ,-position served as a good substrate. These reactions could be extended to carbonylative cycloaddition of the corresponding imines leading to ,-butyrolactam derivatives. The [4,+,1] carbonylative addition of ,,,-unsaturated imines leading to unsaturated ,-lactams was achieved with Ru3(CO)12. © 2008 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 8: 201,212; 2008: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20149 [source]

Rhodium-Catalyzed Asymmetric Aqueous Pauson,Khand-Type Reaction

CHEMISTRY - A EUROPEAN JOURNAL, Issue 13 2005
Fuk Yee Kwong Dr.
Abstract An interesting rhodium-catalyzed asymmetric aqueous Pauson,Khand-type reaction was developed. A chiral atropisomeric dipyridyldiphosphane ligand was found to be highly effective in this system. This operationally simple protocol allows both catalyst and reactants to be handled under air without precautions. Various enynes were transformed to the corresponding bicyclic cyclopentenones in good yield and enantiomeric excess (up to 95,% ee). A study of the electronic effects of the enyne substrates revealed a correlation between the electronic properties of the substrates and the ee value obtained in the product of the Pauson,Khand-type reaction. A linear free-energy relationship was observed from a Hammett study. [source]

Characteristic reactions of group 9 transition metal compounds in organic synthesis

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 3 2009
Iwao Omae
Abstract Group 9 metal compounds in organic synthesis have two characteristic reactions. The first occurs because the group 9 metals have a high affinity to carbon,carbon or carbon,nitrogen ,-bonds. The first type of characteristic reactions in these group 9 metal compounds includes Pauson,Khand reactions, the Pauson,Khand-type reactions ([2 + 2 + 1] cyclization), the other cyclizations and coupling reactions. The second occurs because the group 9 metals have a high affinity to carbonyl groups. The second type of characteristic reactions includes carbonylations such as hydroformylations, the carbonylations of methanol, amidocarbonylations and other carbonylations. The first characteristic reactions are applied for the synthesis of fine chemicals such as pharmaceuticals and agrochemicals. However, the second characteristic reactions are utilized not only for fine chemicals but also for important bulk commodity chemicals such as aldehydes, carboxylic acids and alcohols. Copyright © 2009 John Wiley & Sons, Ltd. [source]