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...     

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。     

Novel 1,3-dipolar cycloaddition of diazocarbonyl compounds to alkynes catalyzed by InCl3 in water

The first intermolecular 1,3-dipolar cycloaddition of diazocarbonyl compounds with alkynes was developed by using an InCl(3) catalyzed cycloaddition in water. The reaction was found to proceed by a domino 1,3-dipolar cycloaddition-hydrogen (alkyl or aryl) migration.     

Oxidant Promoted 1,3-Dipolar Cycloaddition of Pyridinium Ylides to Chalcones for Preparation of 1-Benzoyl-2-arylindolizines

The derivatives of 1-benzoyl-2-arylindolizine were prepared in moderate yields of 41%-78% by CrO3/Et3N promoted 1,3-dipolar cycloaddition of pyridinium N-ylides and chalcones. Under the same conditions, CrO3/Et3N promoted 1,3-dipolar cycloaddition of isoquinolinium N-ylides and chalcones provided the corresponding 1-benzoyl-2-arylpyrrolo[2,1-a]isoquinolines in 45 %-61% yields.     

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.     

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%.     

Binaphthol-derived bisphosphoric acids serve as efficient organocatalysts for highly enantioselective 1,3-dipolar cycloaddition of azomethine ylides to electron-deficient olefins

A variety of chiral bisphosphoric acids derived from binaphthols have been evaluated for enantioselective 1,3-dipolar cycloaddition reactions, revealing that the feature of the linker in the catalysts exerted great impact on the stereoselectivity. Among them, the oxygen-linked bisphosphoric acid 1a provided the highest level of stereoselectivity for the 1,3-dipolar cycloaddition reaction tolerating a wide range of substrates including azomethine ylides, generated in situ from a broad scope of aldehydes and α-amino esters, and various electron-deficient dipolarophiles such as maleates, fumarates, vinyl ketones, and esters. This reaction actually represents one of the most enantioselective catalytic approaches to access structurally diverse pyrrolidines with excellent optical purity. Theoretical calculations with DFT method on the formation of azomethine ylides and on the transition states of the 1,3-dipolar cycloaddition step showed that the dipole and dipolarophile were simultaneously activated by the bifunctional chiral bisphosphoric acids through the formation of hydrogen bonds. The effect of the bisphosphoric acids on reactivity and stereochemistry of the three-component 1,3-dipolar cycloaddition reaction was also theoretically rationalized. The bisphosphoric acid catalyst 1a may take on a half-moon shape with the two phosphoric acid groups forming two intramolecular hydrogen bonds. In the case of maleates, one phosphate acts as a base to activate the 1,3-dipole, and simultaneously, the two hydroxyl groups in the catalyst 1a may respectively form two hydrogen bonds with the two ester groups of maleate to make it more electronically deficient as a much stronger dipolarophile to participate in a concerted 1,3-dipolar cycloaddition with azomethine ylide. However, in the cases involving acrylate and fumarate dipolarophiles, only one hydroxyl group forms a hydrogen bond with the ester functional group to lower the LUMO of the C-C double bond and another one is remained to adjust the acidity and basicity of two phosphoric acids to activate the dipole and dipolarophile more effectively.     

1-Azadienes in heterocyclic synthesis. Reaction of 1-N-alkyl-1-azapenta-1,3-dienes with mesoionic oxazolones

1-N-Alkyl-1-azapenta-1,3-dienes 2 smoothly reacted with various mesoionic oxazolones 1 to afford 3,4-di-hydro-2-pyridones 3 in excellent yields and there was no evidence for the formation of any products arising from the cycloaddition on the carbon? carbon double bond or on the azomethine function.     

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.     

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.     

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.     

Parallel Synthesis of Tetraaryl-4,5-dihydro-1,2,4-triazoles via 1,3-Dipolar Cycloaddition on Soluble Polymer Support

The polymer-supported liquid-phase synthesis of small organic molecules has been a subject of intense research activity. 1,2,4-Triazoles are well known for their antifungal[1] and antibacterial[2] activities. This moiety was also found in potent agonist or antagonist receptor lingands. The synthesis of substituted 1,2,4-triazoles via 1,3-dipolar cycloaddition of imines with nitrilimines is well documented.[3] Herein, we would like to report the first liquid-phase synthesis of 1,3,4,5-tetraaryl-4,5-dihydro-1,2,4-triazoles through a 1,3-dipolar cycloaddition of imines with nitrilimines on PEG support.     

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 C-carbamoyl-1,2,3-triazoles by microwave-induced 1,3-dipolar cycloaddition of organic azides to acetylenic amides

1,3-Dipolar cycloaddition of organic azides 1, 2, or 3 to acetylenic amides 4 or 5 under solvent-free microwave irradiation produced the corresponding N-substituted C-carbamoyl-1,2,3-triazoles 7a-12a in good to excellent yields. Under similar reaction conditions, 1,3-dipolar cycloaddition of diazide 6 and acetylenic amide 4 gave the azido-triazole 13a.     

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.     

Intramolecular 1,3-dipolar cycloaddition of cyclo-1,3-diene-tethered nitrile oxides

Intramolecular 1,3-dipolar cycloaddition of cyclo-1,3-diene- and -1,3,5-triene-tethered nitrile oxides gave tricyclic isoxazolines as a single stereoisomer in most cases. The relative stereochemistry of tricycle-fused isoxazolines resulting from 1,3-dipolar cycloaddition of cyclo-1,3-diene-tethered nitrile oxides is cis-cis, whereas from cyclohepta-1,3,5-triene-tethered nitrile oxides the cis-trans isomer predominates.     

1,3-dipolar cycloaddition on solid supports: nitrone approach towards isoxazolidines and isoxazolines and subsequent transformations

1,3-dipolar cycloaddition reactions of nitrones with alkenes and alkynes are well-studied reactions in solution-phase organic chemistry. However, the number of studies concerned with their application in solid-phase organic synthesis is rather low compared to other 1,3-dipoles, e.g. azides or nitrile oxides. This tutorial review aims to summarise the main approaches towards the application of nitrones in 1,3-dipolar cycloaddition reactions on solid supports in addition to subsequent transformations with polymer-bound isoxazolidines and reactions using polymer-bound catalysts.