- Bifunctional heterogeneous catalysis of silica-alumina-supported tertiary amines with controlled acid-base interactions for efficient 1,4-addition reactions
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We report the first tunable bifunctional surface of silica-aluminasupported tertiary amines (SA-NEt2) active for catalytic 1,4-addition reactions of nitroalkanes and thiols to electron-deficient alkenes. The 1,4-addition reaction of nitroalkanes to electron-deficient alkenes is one of the most useful carbon-carbon bond-forming reactions and applicable toward a wide range of organic syntheses. The reaction between nitroethane and methyl vinyl ketone scarcely proceeded with either SA or homogeneous amines, and a mixture of SA and amines showed very low catalytic activity. In addition, undesirable side reactions occurred in the case of a strong base like sodium ethoxide employed as a catalytic reagent. Only the present SA-supported amine (SA-NEt2) catalyst enabled selective formation of a double-alkylated product without promotions of side reactions such as an intramolecular cyclization reaction. The heterogeneous SA-NEt2 catalyst was easily recovered from the reaction mixture by simple filtration and reusable with retention of its catalytic activity and selectivity. Fur-thermore, the SA-NEt2 catalyst system was applicable to the addition reaction of other nitroalkanes and thiols to various electron-deficient alkenes. The solid-state magic-angle spinning (MAS) NMR spectroscopic analyses, including variable-contact-time 13C cross-polarization (CP)/MAS NMR spectroscopy, revealed that acid-base interactions between surface acid sites and immobilized amines can be controlled by pretreatment of SA at different temperatures. The catalytic activities for these addition reactions were strongly affected by the surface acid-base interactions. 2009 Wiley-VCH Verlag GmbH & Co. KGaA.
- Motokura, Ken,Tanaka, Satoka,Tada, Mizuki,Iwasawa, Yasuhiro
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- The Michael reaction of nitroalkanes with conjugated enones in aqueous media
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The Michael reaction of various nitroalkanes with conjugated enones can be performed in NaOH 0.025 M and in the presence of cetyltrimethylammonium chloride (CTACl) as cationic surfactant, without any organic solvent. Good yields of the products are obtained even with hindered starting materials.
- Ballini, Roberto,Bosica, Giovanna
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- Synthesis, crystal structure, and magnetic properties of 4-(2-methyl-1-azaspiro[4.5]deca-1-oxyl-2-yl)phenol
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The two polymorphic forms (α and β) of the racemate of the title chiral nitroxide radical were separately obtained by changing the composition ratio of the recrystallization solvent (hexane/Et2O). Both polymorphs existed as a racemic compound;
- Uchida, Yoshiaki,Matsuoka, Nagahisa,Takahashi, Hiroki,Shimono, Satoshi,Ikuma, Naohiko,Tamura, Rui
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p. 607 - 616
(2008/09/18)
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- P(RNCH2CH2)3N: Efficient 1,4-addition catalysts
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The 1,4-addition of primary alcohols, higher nitroalkanes, and a Schiff's base of an α-amino ester to α,β-unsaturated substrates produces the corresponding products in moderate to excellent yields when carried out at -63 to 70°C in the presence of catalytic amounts of the nonionic strong bases P(RNCH2CH2)3N (R = Me, i-Pr, i-Bu) in isobutyronitrile. Diastereoselectivity for the anti form of the product is high in the case of the Schiff's base in the absence of lithium ion. These catalysts are easily removed from the product by either column filtration through silica gel or via aqueous workup.
- Kisanga, Philip B.,Ilankumaran, Palanichamy,Fetterly, Brandon M.,Verkade, John G.
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p. 3555 - 3560
(2007/10/03)
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