Transfer of Chirality by the Use of an All Carbon Tether
摘要:
Methylketone side chains can be used to direct the creation atone or more chiral centers, including quaternary centers, by exploiting the ability of the radical xanthate transfer process to mediate six-membered ring formation.
A novel chiral BINOL–silica hybrid has been successfully prepared by the reaction of (S)-BINOL and SiCl4 following by gel polymerization under atmosphere condition. The synthesized catalyst was characterized by elemental analysis, Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Catalytic activity of the chiral BINOL–silica
Ruthenium<i>Lewis</i>Acid-Catalyzed Asymmetric<i>Diels-Alder</i>Reactions: Reverse-Face Selectivity for<i>α</i>,<i>β</i>-Unsaturated Aldehydes and Ketones
作者:Sirinporn Thamapipol、Bettina Ludwig、Céline Besnard、Christophe Saudan、E. Peter Kündig
DOI:10.1002/hlca.201600139
日期:2016.10
Acrolein, methacrolein, methylvinylketone, ethyl vinylketone, 3‐methyl‐3‐en‐2‐one, and divinyl ketone were coordinated to a cationic cyclopentadienyl ruthenium(II) Lewis acid incorporating the electron‐poor bidentate BIPHOP–F ligand. Analysis by NOESY and ROESY NMR techniques allowed the determination of conformations of enals and enones present in solution in CD2Cl2. The results were compared to
Enantioselective Catalytic Diels–Alder Reactions with Enones As Dienophiles
作者:Daniel Carmona、Fernando Viguri、Ainara Asenjo、Fernando J. Lahoz、Pilar García-Orduña、Luis A. Oro
DOI:10.1021/om300346s
日期:2012.6.25
The aqua complexes (SM,RC)-[(η5-C5Me5)M(PROPHOS)(H2O)][SbF6]2 [PROPHOS = (R)-propane-1,2-diylbis(diphenylphosphane); M = Rh (1), Ir (2)] are active catalysts for the asymmetric Diels–Alder reaction between ketones and dienes. At low temperatures, enantioselectivities of up to 89% ee are achieved. The intermediate Lewis acid–dienophile complexes (SM,RC)-[(η5-C5Me5)M(PROPHOS)(MVK)][SbF6]2 (MVK = methyl
Enantioselective Diels-Alder Reaction of Acyclic Enones Catalyzed byallo-Threonine-Derived Chiral Oxazaborolidinone
作者:Ram Shanker Singh、Toshiro Harada
DOI:10.1002/ejoc.200500356
日期:2005.8
An allo-threonine-derived O-(p-biphenylcarbonyloxy)-B-phenyl-oxazaborolidinone is demonstrated to be a powerful and highly enantioselective Lewis acid catalyst for the enantioselective Diels–Alder reaction of simple acyclicenone dienophiles, expanding the scope of ketone dienophiles and dienes. With 10–20 mol % of the catalyst, the Diels–Alder adducts are obtained with up to 94 % ee and high endo
Asymmetric Lewis Acid-Catalyzed Diels−Alder Reactions of α,β-Unsaturated Ketones and α,β-Unsaturated Acid Chlorides
作者:Joel M. Hawkins、Mitch Nambu、Stefan Loren
DOI:10.1021/ol035524t
日期:2003.11.1
[reaction: see text] Conformational analysis, van der Waals attractions, and transition structure calculations are combined to design an asymmetric Lewis acid-catalyzed Diels-Alder reaction for simple acyclic alpha,beta-unsaturated ketones and alpha,beta-unsaturated acid chlorides, giving up to 83 and 92% ee, respectively. The two-point-binding chiral recognition mechanism, Lewis acid-Lewis base coordination