脱质子化1,3环加成石墨烯外在固定位上的贵金属纳米线(英文)

为研究纳米线的形成机理,通过密度泛函理论(DFT)研究了贵金属(铂)在脱质子化1,3-环加成石墨烯上的吸附.研究发现:(1)吸附在1,3-环加成石墨烯上的铂原子引起该结构的脱质子化过程并形成脱质子化1,3-环加成石墨烯;(2)贵金属在脱质子化1,3-环加成石墨烯上的锚定位是氮原子邻位的碳原子,这在邻位碳原子的平均巴德电荷分析(高达1.0e)中得到进一步的证实;(3)铂原子在相邻的脱质子化吡啶炔单元上形成金属纳米线,并且该纳米线比相应的铂团簇稳定得多;(4)电子结构分析表明,铂的吸附并没有从根本上改变脱质子化1,3-环加成石墨烯的电子性质.铂金属的掺杂使得Pt6团簇吸附形成的复合物呈现金属性,而Pt6纳米线形成的复合物则为半金属性.     

1,3-偶极环加成反应修饰卟啉化合物

利用1,3-偶极环加成反应对卟啉大环进行修饰是近年来卟啉研究的一个新热点。环加成产物因在可见光谱长波段范围的特征吸收,在构筑人工光反应体系和用作光动力疗法中的光敏剂等领域有重要应用价值。本文综述了1,3-偶极环加成反应在修饰卟啉化合物方面的研究进展,包括：卟啉作为亲偶极体能与甲亚胺叶立德、硝酮、重氮烷、羰基叶立德、腈氧化物等1,3-偶极子反应生成各种新型杂环稠合卟吩类化合物;卟啉化合物作为1,3-偶极子能与C₆₀等亲偶极体反应,生成β位取代的各种新型卟啉化合物;以及扩展卟啉也可以作为亲偶极体与甲亚胺偶极子发生1,3-偶极环加成反应等。     

1,3-偶极环加成反应与控制自由基聚合结合制备嵌段共聚物的研究进展

炔基与叠氮基的1,3-偶极环加成反应作为点击化学的精髓,反应高效,条件温和.通过它与控制自由基聚合结合,为制备多种拓扑结构嵌段共聚物提供了新途径,所得嵌段共聚物纯度高,分子量分布较窄.本文就1,3-偶极环加成点击反应与3种控制自由基聚合方法相结合在制备线型及非线型嵌段共聚物方面所取得的成就加以综述,并对今后的发展方向做...     

吡啶叶立德与查尔酮1,3-偶极环加成反应制备2-苯基-3-乙酰基中氮茚

报道在氧化剂存在下吡啶叶立德与查尔酮进行1,3-偶极环加成反应, 一锅法合成2-苯基-3-乙酰基中氮茚化合物的方法, 收率37%. 用类似的方法由α-溴代异喹啉季铵盐、查尔酮、碱和氧化剂进行反应, 可一锅法得到1-苯甲酰基-2-苯基-3-乙酰基吡咯并[2,1-a]异喹啉, 收率58%.     

Catalytic enantioselective 1,3-dipolar cycloadditions of nitrones with propioloylpyrazoles and acryloylpyrazoles induced by chiral π-cation catalysts

A chiral copper(II) complex of 3-(2-naphthyl)-l-alanine amide successfully catalyzes the enantioselective 1,3-dipolar cycloaddition reaction of nitrones with propioloylpyrazole and acryloylpyrazole derivatives. The asymmetric environment created by intramolecular π-cation interaction gives the corresponding adducts in high yields with excellent enantioselectivity. This is the first successful method for the catalytic enantioselective 1,3-dipolar cycloaddition of nitrones with acetylene derivatives. The 1,3-dipolar cycloadducts can be stereoselectively converted to β-lactams via reductive cleavage of the N-O bond using SmI(2).     

Substrate-controlled and site-selective [3+2] cycloadditions of N-heterocyclic carbene derived ambident dipoles

2-aryl thiocarbamoyl benzimidazolium and imidazolinium inner salts derived from benzimidazole and imidazoline carbenes are unique ambident C-C-S and C-C-N 1,3-dipolar systems, which undergo highly efficient and site-selective cycloaddition reactions with dimethyl acetylenedicarboxylate or dibenzoylacetylene to furnish spiro(imidazole-2,3'-thiophene) derivatives in excellent yields. When treated with ethyl propiolate, methyl acrylate or acrylonitrile, spiro(imidazole-2,3'-pyrrole) derivatives were formed in good yields. Theoretical studies revealed an asynchronous concerted mechanism for both the C-C-S and C-C-N 1,3-dipolar cycloaddition reactions. The site selectivity in the [3+2] cycloaddition reaction of ambident 1,3-dipoles was predictably regulated by both the electronic and steric effects of dipolarophiles.     

Synthesis of spiropyrrolidinyl-benzoisothiazoline derivatives by 1,3-dipolar cycloaddition of benzoisothiazole-2,2-dioxide-3-ylidenes and azomethine ylide

The new spirocyclic compounds, spiropyrrolidinyl-benzoisothiazoline derivatives were synthesized by the 1,3-dipolar cycloaddition of benzoisothiazole-2,2-dioxide-3-ylidenes and azomethine ylide. The stereochemistry of 1,3-dipolar cycloaddition as well as the stereochemistry of Knoevenagel condensation of benzoisothiazole-2,2-dioxide with aldehydes were studied.     

A library of 3-aryl-4,5-dihydroisoxazole-5-carboxamides

Parallel solution phase methods for the preparation of a 72-membered 3-aryl-4,5-dihydroisoxazole-5-carboxamide library is reported. The reaction order (nitrile oxide 1,3-dipolar cycloaddition followed by amide formation, or vice versa) was investigated both experimentally and computationally to determine which route would result in the highest yields, minimize purification efforts, and give higher 1,3-dipolar cycloaddition regioselectivity. Automated preparative HPLC was used to purify the final products to >or=90% purity on a 10+ mg scale.     

An expedient synthesis of pyrrolidinyl spirooxindole grafted 3-nitrochromanes through 1,3-dipolar cycloaddition reaction of azomethine ylides

A facile one-pot synthesis of pyrrolidinyl-spirooxindole grafted 3-nitrochromanes has been accomplished by 1,3-dipolar cycloaddition (1,3-DC) reaction of 3-nitrochromenes with azomethine ylides generated in situ from isatin and secondary amino acids. The regio- and stereochemical outcome of the cycloaddition reaction was ascertained by X-ray crystallographic analysis.     

On the synthesis of geminally functionalized heterocyclic aminocarboxylic acid esters

The title compounds 5 can be easily obtained by two alternative procedures: 1,3-dipolar cycloaddition to benzamidocinnamates 3 prepared by methanolysis of the corresponding oxazolones 1 or methanolysis of the spirooxazolones 4 synthesized by 1,3-dipolar cycloaddition to oxazolones 1 . Both reaction sequences show the same stereo and regioselectivity.     

Special features of 1,3-dipolar cycloaddition of n-methylazomethinylid to nitrobenzazoles

Synthetic approaches to 1,3-dipolar cycloaddition of N-methylazomethinylid to mononitrobenzazole are described. The geometric and electronic structures have been studied by quantum chemical methods (HF/STO-3 G and B3LYP/6-31 G*) and the reactivity indexes of compounds have been estimated. It was shown that 1,3-dipolar cycloaddition of N-methylazomethinylid to the dipolarophile has a polar character and proceeds in accordance with the normal (noninversion) electronic distribution.     

An easy access to novel steroidal dispiropyrrolidines through 1,3-dipolar cycloaddition of azomethine ylides

A facile one-pot synthesis of novel steroidal dispiropyrrolidines has been accomplished by 1,3-dipolar cycloaddition reaction of various azomethine ylides derived from isatin/acenaphthenequinone/ninhydrin and sarcosine with various estrone derivatives as dipolarophiles, in good yield. The effect of various solvents on the 1,3-dipolar cycloaddition reaction are also studied.     

Cycloaddition behavior of 3,4-diazacyclopentadienone dioxides toward bicyclo[2.2.1]heptadiene derivatives. X-ray analysis of the cycloadduct and reaction pathway

The cycloaddition behavior of 2,5-disubstituted 3,4-diazacyclopentadienone dioxide 1a-c toward epoxy-naphthalene ( 2a ) and norbornadiene ( 2b ) was investigated. The structures of the products were determined on the basis of the ¹H- and ¹³C-nmr spectral data and the X-ray analysis data. The stereospecific formation of the endo-exo 1,3-dipolar cycloadducts from 2a indicates that the cycloadduct resulted from the direct 1,3-dipolar cycloaddition. The cycloaddition behavior of 1 toward 2 is discussed on the basis of the PM3-calculated transition-state structures.     

A new chiral phosphine oxide ligand for enantioselective 1,3-dipolar cycloaddition reactions of azomethine ylides

A new set of phosphorus-containing chiral ligands has been synthesized and used with silver(I) for the catalytic asymmetric 1,3-dipolar cycloaddition reaction of azomethine ylides. One of these ligands (POFAM6) was found to produce an effective catalyst for the asymmetric 1,3-dipolar cycloaddition reaction of azomethine ylides with electron deficient dipolarophiles to form pyrrolidines in up to 97% yield and 89% ee.     

Novel quinone-fused corroles

Gallium(III)(pyridine) complex of 5,10,15-tris(pentafluorophenyl)corrole-3-carbaldehyde was used as a precursor of an azomethine ylide, which was trapped in 1,3-dipolar cycloaddition reactions with quinones. Besides the expected dehydrogenated 1,3-dipolar cycloadducts, novel quinone-fused corrole derivatives were also obtained in moderate yields.     

New thiopyran-4-spiro-2′-(1,3-dithiolane):Formation mechanism and crystal structure

Ethylene trithiocarbonate reacted with dimethyl acetylenedicarboxylate to furnish tetramethyl thiopyran-4-spiro-2'-(1,3- dithiolane)-2,3,5,6-tetracarboxylate,a new thiopyran-4-spiro-2'-(1,3-dithiolane) heterocyclic compound,as the minor product together with the major product dimethyl 2-thioxo-1,3-dithiole-4,5-dicarboxylate.The new heterocycle was probably formed through a[2 + 2]cycloaddition between ethylene trithiocarbonate and dimethyl acetylenedicarboxylate followed by a 1,3-dipolar cycloaddition or[...     

区域和立体选择性合成新型螺羟吲哚类化合物

2-芳亚甲基苯并[4,5]咪唑并[2,1-b]噻唑-3-酮与甲亚胺叶立德(经靛红与肌氨酸反应在线生成)进行l,3-偶极环加成反应, 合成了8个新的螺羟吲哚类化合物. 采用元素分析, NMR, IR, 质谱以及X射线单晶衍射等多种谱学技术对产物进行详细表征, 而产物的晶体结构表明了此类反应具有高度的立体选择性和区域选择性.     

Regioselective triphenylamine-tether-directed synthesis of [60]fullerene bis-adducts

The tether-directed regioselective synthesis of equatorial bis-adducts of [60]fullerene via the 1,3-dipolar cycloaddition reaction of azomethine ylides is reported. A mono-[60]fulleropyrrolidine adduct, derived via 1,3-dipolar cycloaddition of azomethine ylides generated in situ upon thermal condensation of triphenylamine bis-aldehyde and an α-amino acid, was isolated and further reacted to yield, exclusively and selectively, the equatorial bis-adduct, which is structurally characterized by appropriate spectroscopic means.     

1,3-Dipolar cycloaddition reactions of 3-acylimino-1-methylbenzimidazolium betaines

3-Acylimino-1-methylbenzimidazolium betaines undergo 1,3-dipolar cycloaddition reactions with activated alkenes (methyl acrylate, acrylonitrile, and fumaronitrile) and methyl propiolate to produce 2-substituted 1-methylbenzimidazoles. The transformation involves the initial formation of a 1,3-dipolar cycloadduct followed by the N? N bond cleavage. The primary adducts can be isolated from the reaction with methyl acrylate and acrylonitrile.