(4-N,N-二甲氨基)-苯基-N-苯基硝酮在高聚物薄膜中光化学反应特性的研究

本工作测定了(4-N,N-二甲氨基)-苯基-N-苯基硝酮(DMAPN)在不同介质中光照后折射率的变化,发现其折射卒随光照时间的增长而明显降低。工作研究了DMAPN在高分子薄膜内的光化学反应与高聚物分子量的关系,在分子量较低的区域,高分子介质对小分子反应的影响是不规则的,而在高分子量区,则随着分子量的增大,反应速率下降,对所得的结果进行了初步讨论。     

N-4-戊烯基硝酮分子内环加成反应区域选择性的理论研究

N-烯基硝酮分子内环加成反应具有区域选择性,如图1.当n=2,R~1=R~2=R~3=H时,即N-4-戊烯基硝酮分子内环加成反应.实验表明,P_a的产率为23％,P_b为47％.我们曾用MINDO/3方法对此反应进行IRC计算,确证P_a、P_b是经由反应物两种不同构象(R_a、R_b)分别得到的产物,并讨论了二反应活化势垒的差别对区域选择性的影响.Tufariello等人认为,P_b的较高产率主要由于2个产物的过渡态的熵差别.为此,本文从理论上考察活化熵和活化焓对区域选择性的影响.     

Synthesis and 1,3-dipolar cycloadditions of a new enantiopure cyclic nitrone

A new enantiopure cyclic nitrone has been efficiently synthesized from a d-glyceraldehyde derivative. Its 1,3-dipolar cycloaddition to different classes of dipolarophiles show complete antifacial selectivity, furnishing highly functionalized enantiopure bicyclic isoxazolidines.     

Solvent‐Free Nucleophilic Addition of N‐Alkylhydroxylamines to Substituted Nitroolefins: Formation of Nitrones by a Tandem process

Nucleophilic addition of 1‐methyl‐2‐arylethylhydroxylamine to substituted β‐nitrostyrene under solvent‐free conditions has led to unexpected nitrones via a tandem process involving 1,4‐addition and elimination.     

Conformational analysis and inversion process in some perhydrodipyrido[1,2‐b;1′2′‐e]‐1,4,2,5‐ dioxadiazines

The stereoselectivity in the cyclodimerization of several six‐membered cyclic nitrones has been investigated. The configurational/conformational analysis of the dimers (i.e. perhydrodipyrido[1,2‐b;1′2′‐e]‐1,4,2,5‐dioxadiazines) has been carried out by NMR spectroscopy. The NMR spectra of the dimers at lower temperatures indicated the presence of either a single or two invertomer(s). The nitrogen inversion barriers are determined using complete line–shape analysis. The invertomer ratios have been used to estimate the relative energies associated with the cis and trans ring fusion in these tricycles. A mechanistic rationale for the observed stereochemistry of the dimerization process has been presented. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis of a novel C-branched polyhydroxylated cyclic nitrone

A novel C-branched polyhydroxylated cyclic nitrone 25,which could be a valuable intermediate for the synthesis of C-branched pyrrolidine iminosugars,was synthesized starting from the commercially available L-arabinose in 29.0% total yield.     

Asymmetric Synthesis of α-Amino Phosphonic Acids Employing the Condensation of Nitrones with Phosphite Derivatives

Abstract

Chiral α-amino phosphonic acid derivatives were synthesized by condensing an enantiomerically homogeneous diazasilyl phosphite with a series of prochiral nitrones. The reactions proceed under mild conditions with moderate to high enantioselectivities and good yields.     

15N chemical shifts of a series of isatin oxime ethers and their corresponding nitrone isomers

In this article, we describe the characteristic ¹⁵N chemical shifts of isatin oxime ethers and their isomer nitrone. These oxime ethers and nitrones are the alkylation reaction products of isatin oximes. In our study, the ¹⁵N chemical shifts observed in these oxime ethers were in the 402–408 (or 22–28) ppm range, although those for their corresponding nitrone series were in the 280–320 (or ?100 to ?60) ppm range. This remarkable difference in ¹⁵N NMR chemical shift values could potentially be used to determine the O‐ versus N‐alkylation of oximes, even when only one isomer is available. In this paper, the differences in ¹⁵N NMR chemical shifts serve as the basis for a discussion about how to distinguish both regioisomers derived from the oximes alkylation. Copyright © 2010 John Wiley & Sons, Ltd.     

氨甲酰基硅烷与硝酮的反应及产物的互变异构

氨甲酰基硅烷可以与硝酮反应, 合成α-(N′-甲基-Ｎ′-三甲基硅氧基)氨基-N,N-二甲基苯乙酰胺(5). 经研究发现, 该产物具有互变异构现象, 提出了这一互变异构体的结构, 并通过1H NMR谱在不同温度(55～－30 ℃)下的数据, 证实了指定结构的存在: 在55 ℃时, 呈现结构(5)的形式; 而在－30 ℃时, 呈现结构(8)的形式, 它们互变的中间体结构则在55～－30 ℃之间随温度的变化而变化.