Oxidation of Amines and Sulfides Catalyzed by an Assembled Complex of Phosphotungstate and Non-Cross-Linked Amphiphilic Polymer
作者:Shiro Ikegami、Yoichi M. Yamada、Hidetsugu Tabata、Hideyo Takahashi
DOI:10.1055/s-2002-35596
日期:——
Oxidation of sulfides and amines was performed with an assembled catalyst of phosphotungstate and non-cross-linked amphiphilic polymer. The reactions proceeded with hydrogen peroxide under organic solvent-free conditions. This insoluble catalyst was reused five times with the turnover number up to 500.
Electronic effects in 1,3-dipolar cycloaddition reactions of N-alkyl and N-benzyl nitrones with dipolarophiles
作者:Andrei Bădoiu、E. Peter Kündig
DOI:10.1039/c1ob06144e
日期:——
1,3-Dipolar cycloadditions afforded fast access to isoxazolidines bearing N-alkyl or N-benzyl substituents. The electronic properties of the substituents in the nitrones define the activity of the dipoles and modulate diastereoselectivity in the non-catalyzed reactions. Using a chiral one-point binding ruthenium Lewis acid catalyst, products were obtained in good yields and with excellent regio-, diastereo-
isoxazolidines were synthesized in good to excellent yields by 1,3-dipolar cycloaddition of N-vinylamide dipolarophiles and nitrones. Strikingly, solvent-free conditions gave high conversion and yields, shortened reaction time, and minimized degradation products. N-Vinyloxazolidin-2-one and its analogues used in these cycloaddition reactions were conveniently prepared in excellent yields by a modified
Oxidation of allylic alcohols, amines, and sulfides mediated by assembled triphase catalyst of phosphotungstate and non-cross-linked amphiphilic copolymer
A novel catalyst PWAA, an assembled complex of phosphotungstic acid (H3PW12O40) and a non-cross-linked copolymer of N-isopropylacrylamide with an ammonium, was developed. It is an amphiphilic, cross-linked, and supramolecular insoluble complex and showed catalytic activity on oxidation with aqueous hydrogen peroxide. PWAA, used in 2.7 x 10(-5) -2.0 x 10(-3) mol equiv., catalyzed oxidation of allylic alcohols, amines, and sulfides efficiently. The turnover number (TON) of PWAA reached up to 35,000. PWAA showed a good stability in organic/aqueous media and was reused three to five times. (C) 2004 Elsevier Ltd. All rights reserved.