Mukaiyama–Michael Reactions with Acrolein and Methacrolein: A Catalytic Enantioselective Synthesis of the C17–C28 Fragment of Pectenotoxins
摘要:
Enantioselective iminium-catalyzed reactions with acrolein and methacrolein are rare. A catalytic enantioselective Mukaiyama-Michael reaction that readily accepts acrolein or methacrolein as substrates, affording the products in good yields and 91-97% ee, is presented. As an application of the methodology, an enantioselective route to the key C17-C28 segment of the pectenotoxin using the Mukaiyama-Michael reaction as the key step is described.
Tetrakis(trifluoromethanesulfonyl)propane: highly effective Brønsted acid catalyst for vinylogous Mukaiyama–Michael reaction of α,β-enones with silyloxyfurans
Reported herein is a visible‐light‐mediated radical approach to the α‐alkylation of ketones. This method exploits the ability of a nucleophilic organocatalyst to generate radicals upon SN2‐based activation of alkyl halides and blue light irradiation. The resulting open‐shell intermediates are then intercepted by weakly nucleophilic silyl enol ethers, which would be unable to directly attack the alkyl
An enantioselective, protecting-group-free, totalsynthesis of (+)-Greek tobacco lactone has been achieved by using an organocatalytic Mukaiyama–Michael reaction and a stereospecific oxa-Michael reaction as key steps.
Mukaiyama-Michael Reactions with<i>trans</i>-2,5-Diarylpyrrolidine Catalysts: Enantioselectivity Arises from Attractive Noncovalent Interactions, Not from Steric Hindrance
作者:Eeva K. Kemppainen、Gokarneswar Sahoo、Antti Piisola、Andrea Hamza、Bianka Kótai、Imre Pápai、Petri M. Pihko
DOI:10.1002/chem.201304240
日期:2014.5.12
the predicted and observed stereoselectivities. The analysis of intermolecular forces reveals that the enantioselectivity is mostly due to stabilizing noncovalentinteractions between the reacting partners, not due to sterichindrance. The role of attractivenoncovalentinteractions in enantioselective catalysis may be underappreciated.
Highly Diastereoselective Three-Component Vinylogous Mannich Reaction between Isoquinolines, Acyl/Sulfonyl Chlorides, and Silyloxyfurans
作者:Philippe Hermange、Marie Elise Tran Huu Dau、Pascal Retailleau、Robert H. Dodd
DOI:10.1021/ol901452d
日期:2009.9.17
Reaction of an isoquinoline, a silyloxyfuran, and an acyl or sulfonylchloride provides easy access to a wide variety of isoquinolinobutyrolactones with excellent yields and diastereoselectivites (R*,R* isomer), even in the case of formation of quaternary centers (i.e., R3 or R4 = Me). Moreover, the use of a chiral auxiliary allowed formation of a single stereoisomer in 96% yield. This represents the
Asymmetric Catalytic [4 + 2] Cycloaddition via Cu–Allenylidene Intermediate: Stereoselective Synthesis of Tetrahydroquinolines Fused with a γ-Lactone Moiety
A decarboxylative formal [4 + 2] cycloaddition reaction between ethynyl benzoxazinanones and 5-substituted 2-silyloxyfurans catalyzed by chiral Cu–Pybox complex is described. This method allows the formation of intriguing tetrahydroquinolines fused with a butyrolactone moiety featuring three contiguous chiral centers in high yields with excellent diastereo- and enantioselectivities in most cases. The