Manganese(III) acetate mediated synthesis of 3-trifluoroacetyl-4,5-dihydrofurans and 3-(dihydrofuran-2(3H)-ylidene)-1,1,1-trifluoroacetones by free radical cyclization. Part 1

2-Trifluoroacetyl-4,5-dihydrofurans were obtained by manganese(III) acetate mediated radical cyclization of trifluoromethyl-1,3-dicarbonyl compounds (1a-c) with conjugated alkenes (2a-h). The reaction of 1,1,1-trifluoropentane-2,4-dione (1a) with propenylbenzene and 1,1-diphenyl-1-butene surprisingly yielded 3-(dihydrofuran-2(3H)-ylidene)-1,1,1-trifluoroacetones besides 3-trifluoroacetyl-4,5-dihydrofurans.     

Synthesis of large generation poly(propyl ether imine) (PETIM) dendrimers

Large generation poly(propyl ether imine) (PETIM) dendrimers are synthesized in iterative synthetic cycles of two reductions and two Michael addition reactions. Dendrimers up to sixth generation, containing up to 128 peripheral functionalities, are synthesized. Growth of the PETIM dendrimers, possessing a tertiary amine as the branch juncture and an ether as the linker component, is assessed systematically by routine spectroscopic methods. The peripheries of these dendrimers possess either alcohols, amines, carboxylic acids, esters, or nitriles, thereby opening up possibilities for varied studies involving PETIM dendrimers.     

基于方向信息测度的最小模糊度准则边缘检测

将像素点的方向信息测度作为判别边缘点的特性指标,借用Huang等构造的自适应确定分割阈值的思想,本文提出了一种基于方向信息测度的最小模糊度准则边缘检测方法。文中提出的方法,一方面由于采用了方向信息测度,可以很好地将边缘点和非边缘点区分开来;另一方面通过最小化模糊度,自适应地将给定图像的所有像素点按照方向信息测度分成两类,从而达到提取边缘的目的。实验结果证明,我们提出的方法能够很好地判别边缘点,有效地提取图像的边缘。     

Unusual Reactivities of ortho-Hydroxy-β-nitrostyrene

Nitrostyrene derivatives are widely used in organic syntheses as a substrate for Michael addition, photoisomerization and cycloaddition. In contrast, ortho-hydroxy derivatives exhibit unusual behaviors in these reactions. Conjugate addition proceeded upon treatment of the ortho-hydroxy-β-nitrostyrene with an amine; however, subsequent C–C bond cleavage readily occurred to afford the corresponding imine. Moreover, conversion of the trans-isomer to a cis-isomer did not occur efficiently, even when UV light was irradiated. We studied these unusual behaviors of β-nitrostyrene, focusing on the role of the ortho-hydroxy group.     

微波-同时蒸馏萃取分离肉桂挥发性成分分析

经粉碎的肉桂干燥树皮置于去离子水中微波加热处理后,用自制的同时蒸馏-萃取装置,以重蒸乙醚为溶剂将试样中的挥发组分萃取分离。用旋转蒸发器除去乙醚后即得到含有试样中挥发组分的透明的黄色液体,收得率为6.5%,应用GC/MS法对黄色液体的组分进行定性和定量分析。借助于联机的计算机和相关软件并用峰面积-归一化计算测得其中共有27个化合物,其中含量最高的是肉桂醛,达94.36%。另取部分上述挥发油(即黄色液体),用加成分解法将其中肉桂醛转化为一种加成产物以沉淀形式析出,即将黄色液体与NaHSO3共置于微波炉中,在不超过10℃的条件下处理直至加成物完全析出。将此加成物分出,并用0.1 mol.L-1盐酸进行水解处理,使加成物恢复成纯度较高的肉桂醛,用IR及MS对其组成及结构作进一步确认。     

Regioselective nucleophilic ring-opening reaction of chiral epoxyallyl alcohols: a ready access to the pyran core of macrolactin 3

Herein we report the synthetic strategy towards the pyran core of macrolactin 3 via Sharpless epoxidation, titanium(IV) mediated regioselective ring-opening reaction of epoxyallyl alcohol/epoxy alcohol and oxa-Michael addition as the key steps.     

Nucleophilic imidoesterification of dicarbonyl compounds with cyanatobenzenes through C-C bond formation

Under neat conditions,an efficient method for synthesis of imidoesters has been developed using cyanatobenzenes and dicarbonyl compounds.Nucleophilic addition spontaneously occurred between the two kinds of materials at room temperature with yields of up to 90%.A mechanism directed towards to the imidoester formation has been proposed.