24740-29-2Relevant articles and documents
Ytterbium triflate catalyzed Michael additions of β-ketoesters in water
Keller, Erik,Feringa, Ben L.
, p. 1879 - 1882 (1996)
Michael addition of various β-ketoesters towards enones and α,β-unsaturated aldehydes resulted in quantitative conversion to the corresponding 1,4-adducts by performing the reactions in water in the presence of ytterbium triflate as a water-tolerant Lewis
Development of solvent-driven iron-catalyzed reactions
Itoh, Toshiyuki
, p. 1373 - 1395 (2016/08/06)
The possibility of solvent-driven iron-catalyzed reactions has been investigated using ionic liquids and acetonitrile as key solvents. Three iron-catalyzed reactions, the intramolecular cyclization of cyclopropane dithioacetals, the [2+2]-cycloaddition of (trans)-anethole, and the [2+3]-type cycloaddition of styrene derivatives with 1,4-benzoquinone, were first developed using acetonitrile as solvent in the presence of 3～5 mol% of Fe(ClO4 )3 ?Al2 O3 or Fe(BF4 )2 ?6H2 O under air conditions. In particular, we found the rapid cycloaddition of iron-catalyzed [2+3]-type cycloaddition of styrene derivatives with 1,4-benzoquinone when the reaction was carried out in an ionic liquid which contained [PF6 ] or [Tf2N] anion. Homo-coupling reaction of aryl or alkynyl Grignard reagent was next discovered using 1 mol% of FeCl3 as catalyst and the reaction also proceeded very rapidly in an ionic liquid. We also found that 3～5 mol% of Fe(ClO4 )2 ?Al2 O3 or Fe(BF4 )2 ?6H2 O-successfully catalyzed Friedel-Crafts type alkylation of indoles or pyrroles with vinyl ketones or α-aryl-β-silylalcohol. In particular, the reaction of chiral α-aryl-β-silylalcohol with indole using Fe(ClO4 )3 ?nH2 O as catalyst proceeded with retention of the configuration of stereochemistry of the hydroxyl group. Then, we discovered the first example of iron-catalyzed enantioselective C-S bond formation via Michael addition of thiols to (E)-3-crotonoyloxazolidin-2-one using 10 mol% of Fe(BF4 )2 /Pybox. We further demonstrated that Fe(ClO4 )3 ?Al2 O3 -catalyzed the Nazarov type cyclizations of thiophene, pyrrole, indole, benzofuran, and benzo[b]thiophene derivatives using ionic liquids as solvent. Solvents have been recognized as a by-player in chemical reactions in the process of "optimization of reaction conditions". However, further investigation of the solvent-driven iron-catalyzed reaction will allow discovery of useful reactions for organic syntheses.
