(Polyfluoro)silane-mediated generation of azomethine ylides from imines and their cycloaddition leading to N-heterocycles

The novel generation and cycloaddition of azomethine ylides from an α-(trimethylsilyl)imine using (polyfluoro)silanes is described. The method was successfully applied to an efficient one-pot process. Namely, an azaallyl anion, generated by abstraction of the hydrogen α to an imino nitrogen, was treated with a di- or trifluorosilane to give an azomethine ylide intermediate below room temperature. The generated 1,3-dipole was smoothly trapped with dipolarophiles to afford nitrogen-containing five-membered heterocycles in good yields.     

1,3-Dipolar cycloaddition of azomethine ylides generated from aziridines in supercritical carbon dioxide

The 1,3-dipolar cycloaddition of azomethine ylides with DMAD in supercritical carbon dioxide is reported. The photolysis reaction conditions were optimized with a suitable adjustment of pressure, temperature, irradiation time and co-solvent concentration leading to a more efficient reaction than in neat acetonitrile. Similar results were observed using thermal reaction conditions. Supercritical carbon dioxide with a minute co-solvent addition is shown to be a very efficient medium for promoting this type of cycloadditions.     

1,3-Dipolar cycloaddition of phthalazinium ylides to 5-arylidene-2-spirocyclohexane-1,3-dioxane-4,6-diones

Tetrahydrospiropyrrolo[2,1-a]phthalazines were synthesized by the reaction of 5-arylidene-2-spirocyclohexane-1,3-dioxane-4,6-diones with phthalazinium ylides. One of the reaction products, viz., 3-ethoxycarbonyl-2-(4-methoxyphenyl)-2′,2′-pentamethylene-1,2,3,10b-tetrahydrospiro[pyrrolo[2,1-a]phthalazine-1,5′-[1,3]dioxane]-4′,6′-dione, was studied by X-ray diffraction. The spectroscopic characteristics of the reaction products are discussed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2362–2365, October, 2005.     

1,3-Dipolar cycloaddition reactions of cyclooctyne with azomethine ylides

Cyclooctyne smoothly underwent 1,3-dipolar cycloaddition with aziridines and pyridinium ylides to afford the corresponding pyrroles and indolizines in moderate to good yields.     

1,3-Dipolar cycloaddition reactions of azomethine ylides and alkynes

Chemistry of Heterocyclic Compounds - In this review, we consider 1,3-dipolar cycloaddition reactions between azomethine ylides and alkynes, resulting in the formation of pyrroles, as well as their...     

Diastereoselective lithium salt-assisted 1,3-dipolar cycloaddition of azomethine ylides to the fullerene C60

An efficient method for the diastereoselective synthesis of 5-substituted 3,4-fulleroproline esters based on the lithium salt-assisted cycloaddition of azomethine ylides has been developed. A series of the fulleroproline esters containing either electron donating or electron withdrawing substituents was prepared with high yields and diastereoselectivities provided by the S-trans-configuration of ylide generated in situ from the corresponding Schiff base in the presence of a lithium salt and base. This method provides easy preparation of 3,4-fulleroproline derivatives suitable for fullerene-based peptide synthesis.     

Asymmetric Synthesis of Tetrahydroisoquinoline Derivatives through 1,3-Dipolar Cycloaddition of C,N-Cyclic Azomethine Imines with Allyl Alkyl Ketones

A [3 + 2] 1,3-Dipolar cycloaddition of C,N-cyclic azomethine imines with allyl alkyl ketones has been achieved. The reaction proceeds under mild conditions and tolerates a wide range of functional groups. An array of tetrahydroisoquinoline derivatives is generally constructed with good diastereoselectivities and enantioselectivities (up to >25:1 dr, >95% ee). Moreover, the absolute configuration of the product was previously determined by using the quantum electronic circular dichroism calculation and ECD spectrum method.     

1,3-Dipolar cycloaddition of stabilised and non-stabilised azomethine ylides derived from uracil polyoxin C (UPoC): access to nikkomycin analogues

Cascade thermal and decarboxylative cycloaddition reactions of uracil polyoxin C (UPoC) with mono- and di-carbonyl compounds in the presence of a dipolarophile leads, via stabilised and non-stabilised azomethine ylides respectively, to a series of polyoxin cycloadducts related to Nikkomycin B in good to excellent yields and high diastereoselectivity.     

Isomerization and 1,3-dipolar cycloaddition of gem-difluorinated NH-azomethine ylides in the reaction of difluorocarbene with diarylmethanimines

Reaction of difluorocarbene with diarylmethanimines leads to the formation of gem-difluorinated NH-azomethine ylides, two types of competing transformations of which are found to be characteristic: a formal 1,2-H shift into N-(difluoromethyl)imines and 1,3-dipolar cycloaddition to electron-deficient multiple bonds. α,α,α-Trifluoroaceto-phenones are efficient dipolar traps for difluoro NH-ylides, the addition of which to the dipole proceeds regioselectively with the formation of 4-fluoro-2,5-dihydrooxazoles. According to the quantum-chemical calculations by the DFT B3LYP/6-31G* method, 1,3-dipolar cycloaddition of difluorinated NH-azomethine ylides to a C=O bond with the formation of 4-fluoro derivatives of oxazole has lower barrier of activation than the reaction, leading to another regioisomer; the formal 1,2-H shift in the ylide occurs intermolecularly with participation of an imine, a precursor of the ylide.     

A novel Fe(II)/diaryl prolinol catalyzed asymmetric 1,3-dipolar cycloaddition of azomethine ylides with alkenes

A novel Fe(II)/diaryl prolinol catalyzed asymmetric 1,3-dipolar cycloaddition of azomethine ylides with alkenes has been developed. In the presence of FeCl₂ (10 mol %) and α,α-bis(3,5-bistrifluoromethylphenyl)prolinol L1 (10 mol %), [3+2] cycloaddition of azomethine ylides with electronic-deficient olefins underwent smoothly in CH₃CN at room temperature to generate the desired endo-adducts in moderate to good yields and enantioselectivities. This is the first example of Fe(II)/N,O-ligand (L1) catalyzed 1,3-dipolar enantioselective cycloaddition reaction of azomethine ylides.     

The 1,3 dipolar cycloaddition of azomethine ylides to graphene,single wall carbon nanotubes,and C60

Herein, we perform a comparative study on the addition of azomethine ylides to graphene, carbon nanotubes, C₆₀, ethene, pyrene and a C₄₈H₁₈ hydrocarbon. The calculated binding energies and free energy corrections suggest that the addition of azomethine ylide to perfect graphene is not spontaneous (ΔG > 0). However, the presence of Stones–Wales defects significantly increases reactivity: the binding energy between SW‐defective graphene and the azomethine ylide is 0.83 eV, close to that determined for a (5,5) SWCNT. The electronic properties of the sheet are not modified by the 1,3 cycloaddition. The binding energies determined for the addition of an azomethine ylide to a (5,5) SWCNT are significantly lower than previously reported. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

1,3-Dipolar cycloaddition in the synthesis of pyrazolyl-substituted nitronyl nitroxides

A new approach to the synthesis of polyfunctional pyrazolyl-substituted nitronyl nitroxides was developed based on the presynthesized pyrazole derivatives prepared by 1,3-dipolar cycloaddition. The structures of the resulting mono-and biradicals were confirmed by X-ray diffraction. Dedicated to Academician A. L. Buchachenko on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2105–2116, September, 2005.     

1,3-Dipolar cycloaddition reactions of benzo[b]thiophene 1,1-dioxide with azomethine ylides

New pyrrolo derivatives of benzo[b]thiophene 1,1-dioxide have been synthesised via 1,3-dipolar cycloaddition reactions. Reaction of benzo[b]thiophene 1,1-dioxide with stabilised azomethine ylides gave products in low yield but high stereoselectivity whereas reaction with non-stabilised azomethine ylides gave high overall yields but low stereoselectivity.     

1,3-偶极环加成法合成异噁唑啉新化合物及其生物活性的研究

以N-甲羟胺硫酸盐和芳香族羰基化合物为主要原料合成了一系列不同的1,3-偶极化合物, 并合成了四种不同的单取代苯乙烯. 以该系列1,3-偶极化合物和单取代苯乙烯为主要中间体, 采用1,3-偶极环加成反应合成了一系列异噁唑啉类新化合物. 同时研究了1,3-偶极化合物与单取代烯发生的1,3-偶极环加成反应, 该合成过程为理想的绿色反应, 合成产物是5位取代异噁唑啉. 通过质谱和核磁共振等表征了化合物的化学结构. 同时对系列异噁唑啉类新化合物进行了实验室内植物生物活性的测试, 发现了对植物灰霉病有效的新化合物.     

Direct construction of novel dispiro heterocycles through 1,3-dipolar cycloaddition of azomethine ylides

The 1,3-dipolar cycloaddition of 2-oxo-(2H)-acenaphthylen-1-ylidene-malononitrile and 2-fluoren-9-ylidene-malononitrile as dipolarophiles have been investigated for the first time with the azomethine ylides generated in situ from N-substituted isatin and sarcosine to furnish novel dispiro heterocycles. The structure and relative stereochemistry of both types of cycloadducts were confirmed by single crystal X-ray diffraction, as well as with the help of ¹H, ¹³C, and HMBC spectroscopic methods.