Enantioselective Folding of Enynes by Gold(I) Catalysts with a Remote <i>C</i><sub>2</sub>-Chiral Element
作者:Giuseppe Zuccarello、Joan G. Mayans、Imma Escofet、Dagmar Scharnagel、Mariia S. Kirillova、Alba H. Pérez-Jimeno、Pilar Calleja、Jordan R. Boothe、Antonio M. Echavarren
DOI:10.1021/jacs.9b06326
日期:2019.7.31
Chiral gold(I) catalysts have been designed based on a modified JohnPhos ligand with a distal C2-2,5-diarylpyrrolidine that creates a tight binding cavity. The C2-chiral element is close to where the C-C bond formation takes place in cyclizations of 1,6-enynes. These chiral mononuclear catalysts have been applied for the enantioselective 5-exo-dig and 6-endo-dig cyclization of different 1,6-enynes
Asymmetric Au-catalyzed cycloisomerization of 1,6-enynes: An entry to bicyclo[4.1.0]heptene
作者:Alexandre Pradal、Chung-Meng Chao、Patrick Y Toullec、Véronique Michelet
DOI:10.3762/bjoc.7.116
日期:——
A comprehensive study on the asymmetric gold-catalyzedcycloisomerizationreaction of heteroatom tethered 1,6-enynes is described. The cycloisomerizationreactions were conducted in the presence of the chiral cationic Au(I) catalyst consisting of (R)-4-MeO-3,5-(t-Bu)(2)-MeOBIPHEP-(AuCl)(2) complex and silver salts (AgOTf or AgNTf(2)) in toluene under mild conditions to afford functionalized bicyclo[4
Benzimidazolium‐ and Benzimidazolilydene‐Capped Cyclodextrins: New Perspectives in Anion Encapsulation and Gold‐Catalyzed Cycloisomerization of 1,6‐Enynes
introducing a N‐heterocycliccarbene cap onto cyclodextrins has been devised. The benzimidazolium intermediates were found to behave as receptors towards cavity matching anions. The corresponding C1‐ and C2‐symmetrical regioisomeric carbenegold(I) complexes have been tested in a benchmark asymmetric cycloisomerization of 1,6‐enynes. Up to 50 % ee was achieved for the enantioselective cycloisomerization of
α‐ and β‐cyclodextrinderivatives equipped with one or two PIII‐containing handles behave as enantiodiscriminating ligands in the gold‐catalyzed cycloisomerization of prochiral N‐tethered 1,6‐enynes. Enantioselectivity was found to be dependent on the ability of the ligand to position the metal‐coordinated substrate inside the cavity.