Rhodium(I)-Catalyzed Carbonyl Allenylation versus Propargylation via Redox Transmetalation Across Tetragonal Tin(II) Oxide
作者:Moloy Banerjee、Sujit Roy
DOI:10.1021/ol0493352
日期:2004.6.1
[reaction: see text] A reagent combination of beta-SnO and catalytic [Rh(COD)Cl](2) in THF-H(2)O promotes the reaction of propargyl bromides and aldehydes and directs the regioselectivity toward the formation of either allenicalcohols or homopropargylicalcohols. This highly regioselective either/or transformation proceeds via a transmetalation from rhodium to tin, in which metallotropic rearrangement
Ligand-Controlled Copper-Catalyzed Highly Regioselective Difluoromethylation of Allylic Chlorides/Bromides and Propargyl Bromides
作者:Yang Gu、Changhui Lu、Yucheng Gu、Qilong Shen
DOI:10.1002/cjoc.201700594
日期:2018.1
Highly regiodivergent copper‐catalyzed allylic/propargylic difluoromethylation reactions by employing different ligands are described. When 5,6‐dimethyl‐1,10‐phenanthroline was used as the ligand, exclusively α‐difluoromethylated products were obtained, while γ‐selective difluoromethylated products were generated when N‐heterocyclic carbene‐SIPr was used as the ligand. Likewise, high α‐ vs. γ‐selectivities
has been developed from the cyclization of 2‐propynyl‐1,3‐dicarbonyl compoundscatalyzed by potassium tert‐butoxide, copper(II) trifluoromethanesulfonate and triphenylphosphine using methanol/dichloromethane as the solvent under very mild conditions. Moreover, dihydrofurans could be easily transformed into the corresponding furans in the presence of trifluoroacetic acid.
Nature of the Intermediates in Gold(I)-Catalyzed Cyclizations of 1,5-Enynes
作者:Verónica López-Carrillo、Núria Huguet、Ángeles Mosquera、Antonio M. Echavarren
DOI:10.1002/chem.201101749
日期:2011.9.19
The carbene or carbocationic nature of the intermediates in the gold-catalyzedcycloisomerization of 1,5-enynes can be revealed, depending on the ligands on the gold catalysts. Gold complexes with highly electron-donating ligands promote reactions that proceed via intermediates with carbene-like character, leading to products with a bicyclo[3.1.0]hexene skeleton. The intermediate cyclopropyl endo-gold