含吡唑基查尔酮的[2+2]环加成反应研究

在氢氧化钾存在下,用4-甲酰基吡唑类化合物和取代苯乙酮发生反应得到含吡唑基查尔酮的[2+2]环加成产物,对其进行了波谱表征,并对其反应机理进行了讨论.     

Diastereo- and enantioselective palladium-catalyzed dearomative [4+2] cycloaddition of 3-nitroindoles

A Pd-catalyzed asymmetric decarboxylative [4+2] cycloaddition of 3-nitroindoles and vinyl benzoxazinanones is developed through a dearomatization approach. The reaction provides an efficient protocol for constructing a series of chiral tetrahydro-5H-indolo[2,3-b]quinolines in high yields and with excellent diastereo- and enantioselectivities.     

Concise approach to the core of englerin A via an organocatalytic [4+3] cycloaddition reaction

A concise enantioselective synthesis of diversely functionalized advanced intermediates comprising the tricyclic skeleton of englerin A and related oxygen-bridged guaianes has been successfully accomplished, which features a Harmata organocatalytic [4+3] cycloaddition reaction.     

Oligonucleotides containing arylacetylene residues: Synthesis and post-synthetic modification via [3+2] cycloaddition

The synthesis of a phosphoramidite reagent for 5′-modification of oligonucleotides by introducing an arylacetylene residue has been described. Using the reaction with 3-(perylen-3-yl)propyl azide as an example, it was shown that the acetylene derivatives of oligonucleotides synthesized using this reagent undergo Cu^I-catalyzed [3+2] dipolar cycloaddition. Fluorescent conjugates were obtained in high yields and characterized by mass spectra. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1220–1226, July, 2006.     

Synthesis and properties of azoles and azole derivatives 63. Quantum-chemical analysis of [2+3] cycloaddition of 3-nitro-1-propene with triphenylnitrone

Quantum-chemical calculations using the semiempirical AM1/COSMO method have shown that the regioselectivity of [2+3] cycloaddition of 3-nitro-1-propene to triphenylnitrone is a function of thermodynamic factors. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp.913–917, June, 2008.     

Diastereoselective synthesis of functionalized tetrahydro-γ-carbolines via a [3 + 3] cycloaddition of 2,2′-diester aziridines with β-(indol-2-yl)-α,β-unsaturated ketones

A Sc(OTf)₃-catalyzed [3 + 3] cycloaddition of 2,2′-diester aziridines with β-(indol-2-yl)-α,β-unsaturated ketones was developed, affording polysubstituted tetrahydro-γ-carbolines in single diastereoisomers in good to excellent yields.     

Thiourea-catalyzed asymmetric formal [3+2] cycloaddition of azomethine ylides with nitroolefins

A chiral thiourea catalyst possessing an amine function catalyzes an asymmetric [3+2] cycloaddition of azomethine ylides to nitroolefins to provide highly functionalized pyrrolidines with high diastereo- and enantioselectivities (up to 98:1:1 dr, 92% ee). The reaction proceeds in a stepwise manner consisting of Michael addition and subsequent intramolecular aza-Henry reaction. Both reactions are promoted by the thiourea catalyst, and the reaction rate of the latter step is efficiently enhanced by the addition of 2,2,2-trifluoroethanol.     

Lewis acid-mediated [3+2] cycloaddition between hydrazones and olefins

[3+2] Cycloaddition between hydrazones and olefins was accelerated in the presence of a stoichiometric amount of BF₃·OEt₂ or a catalytic amount of Zr(OTf)₄, Hf(OTf)₄, or Sc(OTf)₃ under mild conditions. The corresponding pyrazolidine derivatives were obtained in moderate to high yields using this novel [3+2] Lewis acid catalysis.     

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.     

Catalyst-Free [3+2] Cycloaddition of Isoquinolinium/Pyridinium Ylides and Electron-Deficient Alkenes

The development of simple-to-operate methods for the preparation of indolizidine derivatives are of great importance. A mild one-pot protocol for the [3+2] cycloaddition of isoquinolinium/pyridinium ylides and electron-deficient alkenes using NaBH₃CN as reductant has been developed. The protocol has a broad substrate scope (more than 40 examples) and provides various novel hexahydroindolizidine derivatives in high yields and excellent diastereoselectivities (up to >20/1).     

Stereospecific [2+2] cycloaddition reactions of diphosphorus with alkenes

[2+2] Cycloaddition reactions of P₂ with alkenes were predicted to have concerted paths, that is, pseudoexcitation, distorted 2π_s+2π_s, and 2π_s+2π_a processes without any interventions of intermediates. The pseudoexcitation and/or distorted 2π_s+2π_s paths with retention of configuration of alkenes are kinetically preferred to the 2π_s+2π_a path with inversion of configuration. The reactions were predicted from the appreciable difference in the calculated enthalpies of activation to be stereospecific.     

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.     

Synthesis of conformationally restricted nicotine analogues by intramolecular [3+2] cycloaddition

We describe the synthesis of a series of conformationally constrained nicotine analogues 2-5 from appropriate pyridine-containing enals, featuring an intramolecular azomethine ylide-alkene [3+2] cycloaddition. The objective of the current project is to develop new selective nAChRs-targeting ligands. Of the nicotine analogues that we have studied, the conformation-restricting ring B unit can be either a five-membered carbocycle, or a six-membered carbocycle or heterocycle. The present work constitutes a general method for rapid assembly of other related tricyclic nicotine analogues.     

新型多环吡咯并双螺环色满酮氧化吲哚类化合物的合成

以3-羟甲基色酮为原料,在4-二甲氨基吡啶催化下与(Boc)2O反应生成中间体A;A与靛红和脯氨酸生成的1,3-偶极子发生[3+2]环加成反应,合成了8个未见文献报道的多环吡咯并双螺环色满酮氧化吲哚类化合物(3a^3h),收率50%~67%,dr值4/1~2/1,其结构经^1H NMR,^13C NMR和HR-MS(ESI-TOF)表征。确定了化合物3a(CCDC:1973858)和3g(CCDC:1973859)的相对构型。结果表明:该类化合物含有连续5个立体中心,包括两个螺环季碳中心。     

Lewis acid-catalyzed novel [3+2] cycloaddition of methylenecyclopropanes with activated aldehydes or ketones

Methylenecyclopropanes react with activated aldehydes or ketones in the presence of various Lewis acids to give the corresponding [3+2] cycloaddition products having tetrahydrofuran (THF) skeleton in good yields and in some cases with high stereoselectivity.     

氮杂环卡宾催化烯酮与氰基查尔酮的[4+2]不对称环加成反应

报道了氮杂环卡宾催化烯酮与氰基查尔酮的[4+2]不对称环加成反应. 通过L-焦谷氨酸衍生的大位阻卡宾催化烯酮与氰基查尔酮反应,以良好的产率、良好的顺反选择性和优良的对映选择性得到相应的手性多取代二氢吡喃酮类化合物.     

Retention of stereochemistry in gold-catalyzed formal [4+3] cycloaddition of epoxides with arenynamides

Golden opportunity: [4+3] Cycloaddition reactions of arenynamides and epoxides are enabled under gold catalysis and have a broad substrate scope (see scheme; Ms=methanesulfonyl). An S(N) 2-type front-side attack of phenyl at the oxiranyl ring is expected to cause the retention of stereochemistry.     

Palladium-Catalyzed [4+2] Cycloaddition of Vinyl Benzoxazinanones with 1,3-Indanedione: Approach to Spiro-Tetrahydroquinoline Scaffolds

A palladium catalyzed decarboxylative [4+2] cycloaddition of vinyl benzoxazinanones with 2-arylidene indan-1,3-dione has been established, which afford a series of bioactive spiro-tetrahydroquinolines (27 examples) in moderate to good yield (up to 87 %) with high diastereoselectivities. The synthetic utility of this reaction was demonstrated by gram-scale synthesis. Compounds synthesized by this method potently inhibited proliferation in a panel of cancer cell lines. Particularly, the most potent compounds 3 ae , 3 ah , 3 aj and 3 fa displayed selective inhibition of MDA-MB-231 breast carcinoma cells with IC₅₀ values of 1.292, 0.6118, 0.6558, 1.656 and 2.215 μM, respectively.     

Organocatalytic asymmetric [3+2]-cycloaddition of 3-isothiocyanato oxindoles with 1,3,5-trisubstituted-hexahydro-1,3,5-triazines to access spiro-imidazolidinethione-oxindoles

An efficient asymmetric [3 + 2]-cycloaddition reaction of 3-isothiocyanato oxindoles and formaldimines in-situ generated from 1,3,5-trisubstituted-hexahydro-1,3,5-triazines with a cinchona alkaloid-derived thiourea as the catalyst has been developed. A range of biologically important spiro-imidazolidinethione-oxindoles were obtained in excellent yields with good enantioselectivities (up to 99% yield and 93% ee).     

过渡金属催化[2+2+2]环加成反应合成吡啶衍生物

环加成反应可以一步同时构建多个化学键,是目前国内外研究最为活跃的领域之一。相比于传统方法,过渡金属催化的[2+2+2]环加成反应是合成吡啶衍生物的有效手段。本文从反应机理、非手性吡啶化合物合成和手性吡啶化合物合成三个方面阐述了近年来吡啶衍生物的研究情况,涉及Co、Rh、Ru、Fe、Ni、Ti等金属催化体系。