Silylium Ion-Catalyzed Challenging Diels–Alder Reactions: The Danger of Hidden Proton Catalysis with Strong Lewis Acids
作者:Ruth K. Schmidt、Kristine Müther、Christian Mück-Lichtenfeld、Stefan Grimme、Martin Oestreich
DOI:10.1021/ja211856m
日期:2012.3.7
Proton-catalyzed Diels-Alderreactions are not well-documented in the literature, and a representative survey employing TfOH is included here. The outcome of these catalyses is compared with our silylium ion-catalyzed Diels-Alderreactions, thereby clearly corroborating that hidden Brønsted acid catalysis is not operating with our Lewis acid. Several simple-looking but challenging Diels-Alderreactions with exceptionally
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
[GRAPHICS]allo-Threonine-derived O-acyl-B-phenyl-oxazaborolidinones are demonstrated to be powerful and highly enantioselective Lewis acid catalysts for the Diels-Alder reaction of simple acyclic enone dienophiles, expanding the scope of ketone dienophiles and dienes. With 10 to 20 mol % of catalyst, the Diels-Alder adducts are obtained in 76-98% ee with high endo-selectivity. The catalyst exhibits high activity for the reaction with the less reactive beta-substituted dienophiles and the less reactive 1,3-cycohexadiene and 1,3-butadiene derivatives. The application of the catalysts to the Diels-Alder reaction of furan is also described.
Homogeneous catalysis. [Ti(Cp*)2(H2O)2]2+: an air-stable, water-tolerant Diels-Alder catalyst
作者:T. Keith Hollis、N. P. Robinson、B. Bosnich
DOI:10.1021/ja00039a090
日期:1992.6
Homogeneous catalysis. transition metal based lewis acid catalysts.
作者:T. Keith Hollis、William Odenkirk、N.P. Robinson、John Whelan、B. Bosnich
DOI:10.1016/s0040-4020(01)87259-8
日期:1993.1
Transition metal basedLewisacids provide catalysts for the Diels-Alder and Mukaiyama reactions. These catalysts must possess an electron deficient axophilic metal center and a labile coordination position. Unlike traditional Lewisacids, those derived from transition metals can function in the presence of water and have welldefined structures. It is shown how a normally electron rich ruthenium atom