作者:Evelina Colacino、Pierrick Nun、Francesco Maria Colacino、Jean Martinez、Frédéric Lamaty
DOI:10.1016/j.tet.2008.03.091
日期:2008.6
13C MAS nuclear magnetic resonance experiments. We have also studied the temperature profile during the reaction. A comparative study with the corresponding solvent-free microwave activated reaction showed the superiority of the ball-milling method; 31 examples are described, including the synthesis of the anti-aging agent C-phenyl-N-tert-butyl nitrone (PBN) and one of its analogues C-2-pyridyl-N-tert-butylnitrone
Enantioselective 1,3-Dipolar Cycloaddition Reaction of Nitrones with α-(Acyloxy)acroleins Catalyzed by Dipeptide-Derived Chiral Tri- or Diammonium Salts
Organoammonium salts of dipeptide-derived chiral triamines or diamines with TfOH catalyzed the enantioselective 1,3-dipolar cycloaddition reactions of α-acyloxyacroleins with nitrones to give the corresponding adducts in good yields (up to 96%) and with high diastereo- and enantioselectivities (up to 89% ee). Although α-(p-methoxybenzoyloxy)acrolein is rather unstable under the reaction conditions,
(3 + 3) Cycloaddition of Oxyallyl Cations with Nitrones: Diastereoselective Access to 1,2-Oxazinanes
作者:Marie Cordier、Alexis Archambeau
DOI:10.1021/acs.orglett.8b00617
日期:2018.4.20
Oxyallylcations are prepared in situ from readily available α-tosyloxy ketones and act as transient electrophilic partners in (3 + 3) cycloaddition with nitrones. Under mild conditions, this method provides a chemoselective and diastereoselective route to polysubstituted 1,2-oxazinanes. A stepwise process is proposed to rationalize the diastereoselectivity of this transformation.
Chemoselective Electrophilic Oxidation of Heteroatoms by Hydroperoxy Sultams
作者:Feyissa Gadissa Gelalcha、Bärbel Schulze
DOI:10.1021/jo0202841
日期:2002.11.1
of the latter with acidified H2O2. Kinetic studies of the reaction of 1c with 1,4-thioxane 12f suggest that the reaction follows the second-order kinetics, first order in substrate and first order in oxidant with the second-order rate constant several orders of magnitude larger than that of the corresponding reaction with hydrogen peroxide and tert-butyl hydroperoxide without the need for any acid
描述了新型氢过氧阿马酸1b-d的合成及其作为非水介质中广泛的氮,硫和磷杂原子的可再生化学选择性亲电子氧化剂的潜力。1b,c与仲胺10f,g的反应产生羟基磺酰胺2b,c和硝酮11f或自由基11g,这取决于底物和化学计量,而叔胺10a-d给出氧化胺11a-d。化合物1c,d将各种硫醚12a-g平滑地氧化为亚砜13a-g,其通过色谱法以接近定量的产率分离。通过用酸化的H 2 O 2处理2c,从1c再生出1c。1c与1,4-噻吨12f反应的动力学研究表明,该反应遵循二级动力学,底物上的第一级和氧化剂中的第一级,其第二级速率常数比与过氧化氢和叔丁基氢过氧化物的相应反应的速率大几个数量级,而无需任何酸或重金属催化剂。膦14a,b也被1c容易地以定量收率氧化成各自的膦氧化物15a,b。反应可以在环境温度或更低的温度下进行,并且似乎是通过非自由基机理进行的。反应对空间和电子因素均敏感。b容易获得定量产量。
Dynamics in Catalytic Asymmetric Diastereoconvergent (3 + 2) Cycloadditions with Isomerizable Nitrones and α-Keto Ester Enolates
Reaction design in asymmetric catalysis has traditionally been predicated on a structurally robust scaffold in both substrates and catalysts, to reduce the number of possible diastereomeric transition states. Herein, we present the stereochemical dynamics in the Ni(II)-catalyzed diastereoconvergent (3 + 2) cycloadditions of isomerizable nitrile-conjugated nitrones with α-ketoesterenolates. Even in