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
Second Generation CaSH (Camphor Sulfonyl Hydrazine) Organocatalysis. Asymmetric Diels-Alder Reactions and Isolation of the Catalytic Intermediate
作者:Qinghua Li、Wai-Yeung Wong、Wing-Hong Chan、Albert W. M. Lee
DOI:10.1002/adsc.201000438
日期:2010.9.10
chiral auxiliary, Oppolzer’s camphor sultam, is turned into the new generation camphor sulfonyl hydrazine (CaSH II) organocatalyst. With the primary hydrazine functionality external to the tricyclic structure, CaSH II is active towards ketone substrates in asymmetric Diels–Alder reactions. The iminium intermediate of the catalytic cycle was isolated. When it was put back into the solution reaction system
A crucial role in the chemoselective synthesis of primary, secondary, and homoallylic alcohols and of Diels-Alder adducts is played by Lewis acids (LA) in the addition of nucleophiles (Nu) to carbonyl compounds (see scheme; EWG = electron-withdrawing group, EDG = electron-donating group).
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
Recyclable iron(<scp>ii</scp>) caffeine-derived ionic salt catalyst in the Diels–Alder reaction of cyclopentadiene and α,β-unsaturated <i>N</i>-acyl-oxazolidinones in dimethyl carbonate
作者:Di Meng、Dazhi Li、Thierry Ollevier
DOI:10.1039/c9ra04098f
日期:——
Iron(II) triflate was used in combination with caffeine-derived salts as recyclable catalysts for the Diels–Alderreaction run in dimethyl carbonate (DMC) as a green solvent. The catalyst was prepared as an ionic salt from a xanthinium salt and Fe(OTf)2. Various substrates including α,β-unsaturated carbonyl and N-acyloxazolidinone derivatives were reacted with cyclopentadiene using this recyclable
三氟甲磺酸亚铁 ( II ) 与咖啡因衍生盐结合使用,作为可回收催化剂,在碳酸二甲酯 (DMC) 作为绿色溶剂中进行狄尔斯-阿尔德反应。该催化剂由xanthinium盐和Fe(OTf) 2制备为离子盐。使用这种可回收催化剂,包括α,β-不饱和羰基和N-酰基恶唑烷酮衍生物在内的各种底物与环戊二烯反应。使用低催化剂负载量(1 mol%)可提供高产率(高达 99%)的相应环加合物。多次运行证明了催化剂的回收和效率。