[3+2] Cycloaddition of Dimethyl Acetylenedicarboxylate, Methyl Acrylate, and Ethyl Acrylate to 4,5-Dihydro-5-methyl-3H-spiro[benz-2-azepine-3,1'-cyclohexane] N-Oxide

The cycloaddition of methyl acrylate and ethyl acrylate to 4,5-dihydro-5-methyl-3H-spiro[benz-2-azepine-3,1'-cyclohexane] N-oxide proceeds without either regiospecificity or stereospecificity. Eight geometrical isomers of spiro[isoxazolidino[3,2-a]benz-2-azepine-5,1'-cyclohexane] were formed, of which several were isolated as pure samples. The cycloaddition of dimethyl acetylenedicarboxylate proceeds stereoselectively, leading to spiro[isoxazolino[3,2-a]benz-2-azepine-5,1'-cyclohexane] with cis arrangement of the protons at C₍₇₎ and C_(11b).     

Some Chemical Transformations of 4,5-Dihydro-5-methyl-3H-spiro[benz-2-azepine-3,1'-cyclohexane] N-Oxide

The oxidation and reduction of 4,5-dihydro-5-methyl-3H-spiro[benz-2-azepine-3,1'-cyclohexane] N-oxide, the reactions of this N-oxide with methylmagnesium iodide, the sodium salt of diethyl malonate, phenyl isocyanate, and its rearrangement by the action of acetic anhydride lead to N-hydroxy-1,2,3,4-tetrahydrobenz-2-azepines, benz-2-azepine-1-one, and its N-acetoxy derivative as well as isoxazolidino- and oxadiazolidino[3,2-a]benz-2-azepines spirofused with a cyclohexane ring.     

Reactions of 4,5-Dihydro-5-methyl-3H-spiro[benz-2-azepine-3-cyclohexane] N-Oxide with Some Nucleophilic Reagents

4,5-Dihydro-5-methyl-3H-spiro[benz-2-azepine-3-cyclohexane] N-oxide reacted with cyanide ion and isopropyl magnesium bromide to give the corresponding 1-cyano- and 1-isopropyl-4,5-dihydro-5-methyl-3H-spiro[benz-2-azepine-3-cyclohexane], but reaction with phenyl magnesium bromide, benzyl magnesium chloride, and nitromethane gave cyclic hydroxylamines: 1-substituted N-hydroxy-1,2,4,5-tetrahydro-5-methyl-3H-spiro[benz-2-azepine-3-cyclohexanes] which were oxidized to the corresponding nitrones.     

Synthesis and Conversions of Substituted 4,5-Dihydro-3H-spiro[benz-2-azepine-3,1'-cyclohexanes]

On oxidizing substituted 1,2,4,5-tetrahydro-3H-spiro[benz-2-azepine-3,1'-cyclohexanes] with potassium permanganate under phase-transfer catalysis conditions the corresponding 4,5-dihydro derivatives are formed in quantitative yield. By the action of allyl- and benzylmagnesium halides 5-methyl-4,5-dihydro-3H-spiro[benz-2-azepine-3,1'-cyclohexane] is converted into 5-methyl-1,2,4,5-tetrahydro-1-allyl(benzyl)-3H-spiro[benz-2-azepine-3,1'-cyclohexane], and by reaction with phenoxyketene and dichlorocarbene into the corresponding 2-oxoazetidino[4,1-a]- and 1,1-dichloroaziridino[3,1-a]benz-2-azepines.     

On the Question of Zwitterionic Intermediates in the [3 + 2] Cycloaddition Reactions between C-arylnitrones and Perfluoro 2-Methylpent-2-ene

The molecular mechanism of the [3 + 2] cycloaddition reaction between C-arylnitrones and perfluoro 2-methylpent-2-ene was explored on the basis of DFT calculations. It was found that despite the polar nature of the intermolecular interactions, as well as the presence of fluorine atoms near the reaction centers, all reactions considered cycloaddition proceed via a one-step mechanism. All attempts for the localization of zwitterionic intermediates on the reaction paths were not successful. Similar results were obtained regardless of the level of theory applied.     

Reactivity of allenoates toward aziridines: [3+2] and formal [3+2] cycloadditions

The reactivity of buta-2,3-dienoates toward aziridines is reported. Allenoates react as 2π-component in the [3+2] cycloaddition with the azomethine ylide generated from cis-1-benzyl-2-benzoyl-3-phenylaziridine affording 4-methylenepyrrolidines in a site-, regio-, and stereoselective fashion. Under conventional thermolysis, cis- and trans-2-benzoyl-1-cyclohexyl-3-phenylaziridines showed a different reactivity. These aziridines participate in formal [3+2] cycloadditions with allenes via C-N bond cleavage of the three-membered ring leading to functionalized pyrroles.     

Silver Catalyzed Decarbonylative [3 + 2] Cycloaddition of Cyclobutenediones and Formamides

As an important moiety in natural products, N,O-acetal has attracted wide attention in the past few years. An efficient method to construct N,O-acetal has been developed. Using silver catalyst, cyclobutenediones were smoothly converted to the corresponding γ-aminobutenolides in the presence of formamides, in which cyclobutenediones likely proceed with a key decarbonylative [3 + 2] cycloaddition process. In this way, a series of products with varied substituents were isolated in moderate yield and fully characterized.     

[60]富勒烯[2＋2]环加成反应的研究进展

[2＋2]环加成反应是对C₆₀进行化学修饰的重要反应之一, 重点从[2＋2]环加成的典型反应、主要试剂及反应机理等方面进行了综述.     

烯丙胺与C_(60)的热引发[3+2]环加成反应

烯丙胺类化合物与C_(60)在热引发下发生新型的[3+2]环加成反应。反应有较 好的立体选择性。该反应可能经过了热引发的烯丙胺的单电子转移过程，产生烯丙 基自由基，并进一步与C_(60)加成及环化。文中C_(60)衍生物的结构均经过谱学方 法确证。     

有机催化不对称[4+2]环加成反应*

有机催化不对称合成反应是目前国内外研究最为活跃的领域之一。不对称[4+2]环加成（Diels-Alder）反应是合成光学活性环状化合物的有效手段,目前报道的催化不对称Diels-Alder反应的有机催化剂主要有手性咪唑啉酮、手性Br?nsted酸、手性伯胺、金鸡纳碱衍生物等。本文对各类有机催化剂在有机催化不对称Diels-Alder反应中的应用研究进展,以及不对称诱导反应的机理进行了评述。     

新型他克林-吲哚杂二联体的微波促进Husigen[3+2]环加成反应合成及生物活性

以吲哚-3-丙酸和吲哚-3-丁酸为原料,分别与炔丙胺发生缩合反应得到3-(丙酰丙炔胺)吲哚(4a)和3-(丁酰丙炔胺)吲哚(4b),然后4a和4b分别与9-(叠氮基乙基氨基)-1,2,3,4-四氢吖啶类衍生物5a～5c在微波辐射下发生Husigen[3+2]环加成反应得到12个新型乙酰胆碱酯酶抑制剂——他克林-吲哚杂二联体,其结构经NMR,IR和HRMS表征.初步生物活性测试表明,目标化合物均具有较强的乙酰胆碱酯酶抑制能力,其中化合物2b和2d抑制鱼鳐乙酰胆碱酯酶的IC50值分别为1.6和2.0 nmol.L-1,是6T6BA(IC50=11.0 nmol.L-1,鱼鳐)的6.9和5.5倍.     

Metal Free Access to Polysubstituted Pyrimidines via Nitrile Activation and [2+2+2] Cycloaddition

Tf₂O mediated intermolecular / intramolecular [2+2+2] cycloaddition between alkynes and nitriles has been developed for efficient construction of polysubstituted pyrimidines and bicyclopyrimidines. In presence of Tf₂O, aza-allene species were generated in situ through nitrile activation and subsequently participated in the [2+2+2] cycloaddition, which was fully supported by deuteration experiments. The reaction had good substrate extensibility with moderate to excellent yield including trimethylsilylalkynes. The method was utilized as a synthetic tool in the preparation of a luminescent metal complex.     

Synthesis of Substituted and Condensed Tetrahydrospiro[benzo-2-azepinecyclohexanes] from 1-Cyano- and 1-Carbamoyl-5-methyl-4,5-dihydro-3H-spiro[benzo-2-azepine-3,1′-cyclohexanes]

Substitution of the nitrile group by hydroxylamine and hydrazine has been effected in 1-cyanodihydrospiro[benzo-2-azepine-3,1′-cyclohexane]. From the 1-cyano and 1-hydrazino derivatives tetrahydrospiro{1,2,3- and 1,2,4-triazolo[5,1-a]benzoazepine-5,1′-cyclohexanes} have been obtained. It was established that 1-carbamoyldihydrospiro[benzo-2-azepine-3,1′-cyclohexanes] are converted under the conditions of the Hoffmann reaction into spiro{diaziridino[3,1-a]benzo-2-azepine-3,1′-cyclohexane{, and is reduced by sodium borohydride to the tetrahydro derivative. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1033–1037, July, 2005.     

Asymmetric Total Syntheses of Kopsane Alkaloids via a PtCl2-Catalyzed Intramolecular [3+2] Cycloaddition

A concise and asymmetric total synthesis of five kopsane alkaloids that share a unique heptacyclic caged ring system was accomplished. The key transformation in the sequence involved a remarkable PtCl₂-catalyzed intramolecular [3+2] cycloaddition, which allowed for the rapid assembly of pentacyclic carbon skeletons bearing 2,3-quaternary functionalized indoline. Expeditious construction of diverse indoline scaffolds with excellent control of diastereoselectivity demonstrated the broad scope and versatility of this key transformation.     

Scope of the formal [3+2] cycloaddition for the synthesis of substituted 3-arylindanes and related compounds

We report the single step synthesis of several 3-arylindanes and related compounds via a formal [3+2] cycloaddition. A study of the influence of the aromatic ring substitution pattern on the reaction was carried out.     

Electrosynthesis of Dihydropyrano[4,3-b]indoles Based on a Double Oxidative [3+3] Cycloaddition

Oxidative [3+3] cycloadditions offer an efficient route for six-membered-ring formation. This approach has been realized based on an electrochemical oxidative coupling of indoles/enamines with active methylene compounds followed by tandem 6π-electrocyclization leading to the synthesis of dihydropyrano[4,3-b]indoles and 2,3-dihydrofurans. The radical–radical cross-coupling of the radical species generated by anodic oxidation combined with the cathodic generation of the base from O₂ allows for mild reaction conditions for the synthesis of structurally complex heterocycles.