Hemiaminal generated by hydration of ketone-based nitrone as an N,O-centered nucleophile in organic synthesis
摘要:
Isoxazolidines that are useful precursors for beta-amino acids have been prepared relying on intermolecular amino Michael addition-intramolecular S(N)2 displacement employing hydroxylamine or hydrate of ketone-based nitrone as an N- and O-centered binucleophile. (C) 1998 Elsevier Science Ltd. All rights reserved.
Regiochemistry of mercury(II) oxide oxidation of unsymmetrical N,N-disubstituted hydroxylamines
作者:Sk.Asrof Ali、S.M. Azhar Hashmi、Mohammad N. Siddiqui、Mohammed I.M. Wazeer
DOI:10.1016/0040-4020(96)00904-0
日期:1996.11
Mercury(II) oxideoxidation of N,N-disubstituted hydroxylamines with the α and α′ carbon atoms containing one and two hydrogen atoms, respectively, gave aldonitrones in a highly regioselective manner. Removal of the α proton is involved in the rate determining step as shown by primary kinetic isotope effect.
Methyltrioxorhenium-Catalyzed Oxidation of Secondary and Primary Amines with Hydrogen Peroxide
作者:Shigekazu Yamazaki
DOI:10.1246/bcsj.70.877
日期:1997.4
The methyltrioxorhenium-catalyzed oxidation of secondaryamines and primaryamines with hydrogen peroxide has been carried out. The oxidation of secondaryamines afforded nitrones in good-to-excellent yield. Benzylamines were selectively oxidized to oximes, while general primary alkylamines possessing the α-C–H bond gave mixtures of oximes, nitroso dimers, and azoxy compounds.
The oxidation of various N-(o-, m-, p-substituted benzyl)-N-alkylhydroxylamines and their dideuteriobenzyl (PhCD2) counterparts was carried out using mercury(II) oxide and p-benzoquinone (p-BQ) as oxidants. An overwhelming preference for the formation of conjugated nitrones is observed in the oxidation of N-benzyl-N-isopropylhydroxylamines. Considerable intra- and intermolecular kinetic isotope effects and negative rho values in the Hammet plots point towards a mechanistic pathway that involves electron transfer from nitrogen to the oxidant followed by hydrogen abstraction. The conformation of unstable (E)-nitrones, which readily isomerize to the more stable (Z)-nitrones, is deduced from H-1 NMR data. The E = Z isomerization was found to be a bimolecular process. Copyright (C) 2000 John Wiley & Sons, Ltd.
Tungstate-Catalyzed Decarboxylative Oxidation of N-Alkyl-.alpha.-amino Acids: An Efficient Method for Regioselective Synthesis of Nitrones
The tungstate-catalyzed oxidation of N-alkyl-alpha-amino acids with hydrogen peroxide under phase-transfer conditions gives the corresponding nitrones in satisfactory yield.