Exploiting microwave-assisted neat procedures: synthesis of N-aryl and N-alkylnitrones and their cycloaddition en route for isoxazolidines
摘要:
Microwave irradiation allows increasing the speed of several reactions and also offers the possibility of eliminating poisoning organic solvents. In this work we report the microwave-assisted neat synthesis of alpha-phenyl-tert-butylnitrone (PBN) and other alkyl and aryl nitrones and also the rapid synthesis of isoxazolidines resulting from 1,3-dipolar cycloaddition of nitrones to ethyl trans-crotonate. (c) 2008 Elsevier Ltd. All rights reserved.
Magnesium Iodide Promoted Reactions of Nitrones with Cyclopropanes: A Synthesis of Tetrahydro-1,2-oxazines
摘要:
Anhydrous magnesium iodide (MgI2) is shown to be an effective promoter of the "homo 3+2" dipolar cycloaddition of nitrones with 1,1-cyclopropane diesters. In almost all cases the products tetrahydro-1,2-oxazines are formed in excellent yields. The reactions are highly diastereoselective for a cis relationship between the substitutents at the 3- and 6-positions on the tetrahydrooxazine ring. As an alternative to using a preformed nitrone, the reaction may be performed in a 3-component sense by combining an aldehyde, an hydroxylamine, and the cyclopropane in the presence of catalytic MgI2.
Efficient Synthesis of Isoxazolidine-Tethered Monolayer-Protected Gold Nanoparticles (MPGNs) via 1,3-Dipolar Cycloadditions under High-Pressure Conditions
作者:Jun Zhu、Brandon M. Lines、Michael D. Ganton、Michael A. Kerr、Mark S. Workentin
DOI:10.1021/jo702398r
日期:2008.2.1
3-dipolar cycloaddition. At atmospheric pressures, the reaction proceeds slowly (if at all) and makes this reaction impractical for the synthetic modification of the nanoparticles. However, by performing the reaction under the high-pressure conditions, the reaction proceeds efficiently and quantitatively. TEM shows that the use of high pressure does not affect the size of the goldnanoparticle core. The
制备了包含约30%马来酰亚胺封端的十二烷硫醇盐/十二烷硫醇盐配体的马来酰亚胺改性的2.5±0.5nm混合单层保护的金纳米颗粒(2- C 12 MPGN)。的2 -C 12 MPGN用一系列硝酮(的反应一-我)在常压和高压(11 000个大气压)的条件下,形成相应的异恶唑烷改性的纳米粒子(3 -C 12MPGN)通过界面上的1,3-偶极环加成反应。在大气压下,反应进行得很慢(如果有的话),使该反应对于纳米粒子的合成改性不切实际。然而,通过在高压条件下进行反应,反应有效且定量地进行。TEM显示高压的使用不影响金纳米颗粒核的尺寸。通过1 H NMR光谱对3 -C 12 MPGN进行表征,方法是将与使用N-十二烷基马来酰亚胺(4)和相同的硝酮(a - i)形成5的模型反应得到的光谱进行比较。。另外,与具有所有硝酮的2- C 12 MPGN相比,用4进行环加成反应也更容易发生,这表明后者的环境会影响环加成反应。
methodology for the synthesis of nitrones via palladium-catalyzed redox cross-coupling of nitro compounds and alcohols is established. The protocol is a mild, convenient, ligand-free, and scalable synthesis method that can be compatible with various nitro compounds and alcohols. Nitrone is a significant multifunctional platform synthon which can be synthesized directly and efficiently via this tactic from
Exploiting microwave-assisted neat procedures: synthesis of N-aryl and N-alkylnitrones and their cycloaddition en route for isoxazolidines
作者:Marta M. Andrade、Maria Teresa Barros、Rui C. Pinto
DOI:10.1016/j.tet.2008.08.101
日期:2008.11
Microwave irradiation allows increasing the speed of several reactions and also offers the possibility of eliminating poisoning organic solvents. In this work we report the microwave-assisted neat synthesis of alpha-phenyl-tert-butylnitrone (PBN) and other alkyl and aryl nitrones and also the rapid synthesis of isoxazolidines resulting from 1,3-dipolar cycloaddition of nitrones to ethyl trans-crotonate. (c) 2008 Elsevier Ltd. All rights reserved.
Magnesium Iodide Promoted Reactions of Nitrones with Cyclopropanes: A Synthesis of Tetrahydro-1,2-oxazines
作者:Michael D. Ganton、Michael A. Kerr
DOI:10.1021/jo048768f
日期:2004.11.1
Anhydrous magnesium iodide (MgI2) is shown to be an effective promoter of the "homo 3+2" dipolar cycloaddition of nitrones with 1,1-cyclopropane diesters. In almost all cases the products tetrahydro-1,2-oxazines are formed in excellent yields. The reactions are highly diastereoselective for a cis relationship between the substitutents at the 3- and 6-positions on the tetrahydrooxazine ring. As an alternative to using a preformed nitrone, the reaction may be performed in a 3-component sense by combining an aldehyde, an hydroxylamine, and the cyclopropane in the presence of catalytic MgI2.