Neodymium(III)-Mediated Reformatsky-Type Reactions of α-Halo Ketones with Carbonyl Compounds
作者:Stefan F. Kirsch、Clémence Liébert
DOI:10.1002/ejoc.200700240
日期:2007.8
In a neodymium(III) iodide induced process, α-bromo ketones 1 and aldehydes 2 are effectively converted into aldol products 3. This Reformatsky-type reaction proceeds through the formation of a neodymium enolate at room temperature in CH2Cl2. The analogous reaction in the presence of NdBr3/NaI at 50 °C in THF favors the formation of corresponding aldol–Tishchenko products 5 in good yields. Studies
Development of N,N-bis(perfluoroalkanesulfonyl)squaramides as new strong Brønsted acids and their application to organic reactions
作者:Cheol Hong Cheon、Hisashi Yamamoto
DOI:10.1016/j.tet.2010.03.120
日期:2010.6
l groups have been developed and applied to several organic reactions. These squaramides are bench-stable and exhibit much higher reactivities in several organic reactions than squaric acid itself. N,N-Bis(trifluoromethanesulfonyl)squaramide 2a was applied to the Mukaiyama aldol reaction and Mukaiyama Michael reaction. Mechanistic studies revealed that the Brønsted acid might be the predominant catalyst
A new Brønsted acid derived from squaric acid and its application to Mukaiyama aldol and Michael reactions
作者:Cheol Hong Cheon、Hisashi Yamamoto
DOI:10.1016/j.tetlet.2009.03.060
日期:2009.7
of silyl enol ether. The Brønsted acid was further applied to Mukaiyama Michael reaction of α,β-unsaturated ketones. It is noted that catalyst loading of all Mukaiyamareactions was only 1 mol % or less, which demonstrated the high reactivity of this acid. Mechanistic studies implied that the Mukaiyamaaldolreaction might proceed through Brønsted acid catalysis, rather than through Lewisacid catalysis
Kinetic Resolution of β-Hydroxy Carbonyl Compounds via Enantioselective Dehydration Using a Cation-Binding Catalyst: Facile Access to Enantiopure Chiral Aldols
作者:Sushovan Paladhi、In-Soo Hwang、Eun Jeong Yoo、Do Hyun Ryu、Choong Eui Song
DOI:10.1021/acs.orglett.8b00547
日期:2018.4.6
β-hydroxy carbonyl (aldol) compounds through enantioselective dehydration process was developed using a cation-binding Song’s oligoethylene glycol (oligoEG) catalyst with potassium fluoride (KF) as base. A wide range of racemic aldols was resolved with extremely high selectivity factors (s = up to 2393) under mild reaction conditions. This protocol is easily scalable. It provides an alternative approach for
The aldol reaction of trimethylsilyl enol ethers (1-3) with various aldehydes in the presence of a catalytic amount of trimethylsilyl trifluoromethanesulfonate was investigated. With benzaldehyde (4) the β-hydroxycarbonyl compounds were obtained in good yields. The effect of a substituent on the benzene ring was also examined. Aliphatic aldehydes (11, 13, and 14) were found not to be suitable substrates for this catalytic aldol reaction. On treatment with tert-butyldimethylsilyl enol ethers (30 and 31) under the same conditions, benzaldehydes (4, 5, 7, 8) yielded the corresponding aldol products with good threo-selectivity.