Gold(I)-Catalyzed Intermolecular Addition of Carbon Nucleophiles to 1,5- and 1,6-Enynes
作者:Catelijne H. M. Amijs、Verónica López-Carrillo、Mihai Raducan、Patricia Pérez-Galán、Catalina Ferrer、Antonio M. Echavarren
DOI:10.1021/jo8014769
日期:2008.10.3
Gold(I)-catalyzed addition of carbon nucleophiles to 1,6-enynes gives two different type of products by reaction at the cyclopropane or at the carbene carbons of the intermediate cyclopropyl gold carbenes. The 5-exo-dig cyclization is followed by most 1,6-enynes, although those bearing internal alkynes and alkenes react by the 6-endo-dig pathway. The cyclopropane versus carbene site-selectivity can
Bicyclic Cyclopentenones via the Combination of an Iridium- Catalyzed Allylic Substitution with a Diastereoselective Intramolecular Pauson-Khand Reaction
作者:Andreas Farwick、Jens U. Engelhart、Olena Tverskoy、Carolin Welter、Quendolin A. Umlauf née Stang、Frank Rominger、William J. Kerr、Günter Helmchen
DOI:10.1002/adsc.201000706
日期:2011.2.11
Enantioselectivesyntheses of bicyclic cyclopentenones are described. Key steps are an iridium-catalyzedallylicsubstitution and an intramolecular diastereoselective Pauson–Khand reaction. The diastereoselectivity of the Pauson–Khand reaction was found to be crucially dependent on the unit connecting the propargylic and the olefinic parts of the precursor. Very high degrees of diastereoselection were
Exchange of one PCy3 unit of the classical Grubbs catalyst 1 by N-heterocycliccarbene (NHC) ligands leads to "second-generation" metathesis catalysts of superior reactivity and increased stability. Several complexes of this type have been prepared and fully characterized, six of them by X-ray crystallography. These include the unique chelate complexes 13 and 14 in which the NHC- and the Ru-CR entities
Platinum-Catalyzed Cycloisomerization Reactions of Enynes
作者:Alois Fürstner、Frank Stelzer、Hauke Szillat
DOI:10.1021/ja0109343
日期:2001.12.1
PtCl(2) constitutes an efficient and practical catalyst for a set of different atom economical rearrangement reactions of enynes. This includes (i) a formal enyne metathesis reaction delivering 1,3-dienes, (ii) the formation of polycyclic vinylcyclopropane derivatives, and (iii) an unprecedented O-->C allyl shift reaction if unsaturated ethers are employed. Although these transformations produce significantly
(Pentamethylcyclopentadienyl)Iridium Dichloride Dimer {[IrCp*Cl2]2}: A Novel Efficient Catalyst for the Cycloisomerizations of Homopropargylic Diols and N-Tethered Enynes
iridium dichloride dimer [IrCp*Cl2]2}-catalyzed hydroalkoxylation of bis-homopropargylicalcohols provides an efficient access to dioxabicyclo[2.2.1]ketals. The cycloisomerizations proceed under mild conditions, with low catalytic loadings and short reaction times. This new protocol involving an Ir(III) catalyst also promoted the cycloisomerization of nitrogen-tethered 1,6-enynes to give azabicyclo[4