By Daniela Kampen, Corinna M. Reisinger, Benjamin List (auth.), Benjamin List (eds.)
Kerstin Etzenbach-Effers, Albrecht Berkessel: Non-Covalent Organocatalysis in keeping with Hydrogen Bonding: Elucidation of response Paths by means of Computational Methods.- Petri M. Pihko, Inkeri Majander, and Anniina Erkkilä: Enamine Catalysis.- Jennifer L. Moore, Tomislav Rovis: Lewis Base Catalysts 6: Carbene Catalysts.- Amal Ting, Jennifer M. Goss, Nolan T. McDougal, and Scott E. Schaus: Brønsted Base Catalysts.- O. Andrea Wong, Yian Shi: Chiral Ketone and Iminium Catalysts for Olefin Epoxidation.- Alan C. Spivey, Stellios Arseniyadis: Amine, Alcohol and Phosphine Catalysts for Acyl move Reactions.- John B. Brazier, Nicholas C.O. Tomkinson: Lewis Base Catalysts 2 Secondary and first Amine Catalysts for Iminium Catalysis.- Oksana Sereda, Sobia Tabassum, and René Wilhelm: Lewis Acid Organocatalysts.- Daniela Kampen , Corinna M. Reisinger , and Benjamin record: Chiral Bronsted Acids for C Organocatalysis.-
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Additional info for Asymmetric Organocatalysis
However, syn selective aldol reactions are still rare, especially with cyclic ketones. Enamine Catalysis45 4545 6 56: R = solid supports 57: R = TBDPS RO O N SO2Ph H 54 N H N H N 55·HX CO2H N H O R N H N H N H 44 N N N N H R 48,49,51 HO O OH Y anti -aldol, 59 Y X = H, Me, aliphatic Y = Me, aliphatic, aromatic, CO2Et Z = H, CO2R, PO(OR)2 R = H, aliphatic, aromatic, CCl3, 2: isatin X donor, 52 O Z R X O R NH2 acceptor, 53 n -Pr N n -Pr 58 O OH Y R X syn-aldol, 60 O O O O H Selected donors 61 62 23 H O 9 H O O 41 63 O 64 CO2H Ph H 65 O O Selected H 66 acceptors NO2 NBn2 O CN O H 67 2 N H O Scheme 17 Asymmetric aldol reactions with ketone donors Ketone donors bearing a-heteroatoms are particularly useful donors for the enamine-catalyzed aldol reactions (Scheme 18).
In stoichiometric enamine chemistry, the Stork group developed a range of highly useful transformations in the 1950s and 1960s . The first really useful enantioselective enamine-catalyzed process, however, was the intramolecular aldol reaction known as the Hajos–Parrish–Eder–Sauer–Wiechert process [30, 33, 34]. Perhaps surprisingly, although the enamine-based mechanisms had been fully accepted for Nature’s aldolase enzymes, the simple enamine mechanism for this reaction only became universally accepted in the 2000s.
Nevertheless, the anti process is remarkably useful because a variety of highly substituted aldehydes can be accessed in a single operation using only very inexpensive catalysts, such as proline 6 or the phenylalanine-derived imidazolidinone 46 (Scheme 21) [114, 116, 117, 119–121, 188]. 3 Substrate Scope and Current Limitations A particularly acute problem in expanding the substrate scope of the reaction is the scope of the acceptors. The catalyst must somehow differentiate between the donor (to be activated via an enamine) and the acceptor (to be activated only by hydrogen bonding).
Asymmetric Organocatalysis by Daniela Kampen, Corinna M. Reisinger, Benjamin List (auth.), Benjamin List (eds.)