- Aldol Synthesis with an Aqueous Solution of Formalin
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With an aqueous solution of formalin, aldol reaction of trimethylsilyl enol ether proceeds moderately using tetrabutylammonium fluoride (TBAF). Furthermore, catalytic asymmetric hydroxymethylation with trimethoxysilyl enol ether using water tolerant (R)-B
- Ozasa, Nobuko,Wadamoto, Manabu,Ishihara, Kazuaki,Yamamoto, Hisashi
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p. 2219 - 2221
(2007/10/03)
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- Rare Earth Metal Complexes as Water-Tolerant Lewis Acid Catalysts in Organic Synthesis
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Rare earth metal triflates are stable in aqueous media and can act as Lewis acid catalysts in several carbon-carbon bond forming reactions. This article describes some of these reactions; aldol and Mannich-type reactions in aqueous solution, and Friedel-Crafts acylations and Fries rearrangement in organic solvents. The reactions proceeded smoothly in the presence of a catalytic amount of the triflate under mild conditions. Moreover, the catalysts could be recovered after the reactions were completed and could be reused.
- Kobayashi,Hashiya,Ishitani,Moriwaki,Nagayama
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p. 193 - 202
(2007/10/03)
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- Lanthanide Triflates as Water-Tolerant Lewis Acids. Activation of Commercial Formaldehyde Solution and Use in the Aldol Reaction of Silyl Enol Ethers with Aldehydes in Aqueous Media
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Lanthanide trifluoromethanesulfonates (triflates), especially ytterbium triflate (Yb(OTf)3), were found to be stable Lewis acids in water.In the presence of a catalytic amount of lanthanide triflate, formaldehyde in water solution (commercial formaldehyde
- Kobayashi, Shu,Hachiya, Iwao
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p. 3590 - 3596
(2007/10/02)
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- Stabilization of reactive aldehydes by complexation with methylaluminum bis(2,6-diphenylphenoxide) and their synthetic application
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Reactive aldehydes such as formaldehyde and α-chloro aldehydes can be successfully generated by treatment of readily available trioxane and α-chloro aldehyde trimers, respectively, with methylaluminum bis(2,6-diphenylphenoxide) (MAPH), and stabilized as their 1:1 coordination complexes with MAPH. The resulting CH2=O·MAPH complex reacts with a variety of olefins to furnish ene-reaction products with excellent regio- and stereoselectivities. In addition, this complex as well as α-chloro aldehyde-M APH complexes can be utilized as a stable source of gaseous formaldehyde and reactive α-chloro aldehydes, respectively, for the nucleophilic addition of various carbanions (organometallics, enolates, etc.). Formation of reactive aldehyde-MAPH complexes is firmly confirmed by 1H NMR spectroscopy. A space-filling model of aldehyde-M APH complexes implies that formaldehyde and α-chloro aldehydes coordinated with MAPH may be electronically stabilized by two parallel phenyl groups of aluminum ligands.
- Maruoka, Keiji,Concepcion, Arnel B.,Murase, Noriaki,Oishi, Masataka,Hirayama, Naoki,Yamamoto, Hisashi
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p. 3943 - 3949
(2007/10/02)
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- Lanthanide Trifluoromethanesulfonates as Stable Lewis Acids in Aqueous Media. Yb(OTf)3 Catalyzed Hydroxymethylation Reaction of Silyl Enol Ethers with Commercial Formaldehyde Solution
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Silyl enol ethers smoothly react with commercial formaldehyde solution to give the corresponding hydroxymethylated adducts in high yields by the promotion of a catalytic amount of ytterbium(III) triflate (Yb(OTf)3), which is a stable Lewis acid in aqueous
- Kobayashi, Shu
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p. 2187 - 2190
(2007/10/02)
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