Search results for "3-dipolar"
showing 10 items of 44 documents
Regioselective Synthesis of Mono- and Dispiropyrazoline Derivatives via 1,3-dipolar Cycloaddition with Nitrilimines
2016
The 1,3-dipolar cycloaddition reaction of (E,E)-1,3-bis(arylidene)indan-2-one with diarylnitrilimines, generated in situ via dehydrohalogenation of the corresponding hydrazonoyl chlorides , affords predominantly monospiropyrazolines and as a mixture of diastereoisomers. Also dispiropyrazolines are formed in moderate yields. The structure and stereochemistry of cycloadducts were confirmed by 1H and 13C-NMR spectroscopy, elemental analyses data, and single-crystal X-ray diffraction studies of and .
Study of Reactivity in the 1,3-Dipolar Cycloaddition Reactions Leading to New Triazolopyrrolopyrazine Ring Systems
2010
The influence of the structural symmetry of the 2-pi double-reactive-sites component in the 1,3-dipolar cycloaddition reactions, involving nitrilimines as dipoles, was investigated. the experimental data showed that the loss of the symmetry leads to the formation of the monocycloadduct in good yields.
PdII-mediated integration of isocyanides and azide ions might proceed via formal 1,3-dipolar cycloaddition between RNC ligands and uncomplexed azide
2016
Reaction between equimolar amounts of trans-[PdCl(PPh3)2(CNR)][BF4] (R = t-Bu 1, Xyl 2) and diisopropylammonium azide 3 gives the tetrazolate trans-[PdCl(PPh3)2(N4t-Bu)] (67%, 4) or trans-[PdCl(PPh3)2(N4Xyl)] (72%, 5) complexes. 4 and 5 were characterized by elemental analyses (C, H, N), HRESI+-MS, 1H and 13C{1H} NMR spectroscopies. In addition, the structure of 4 was elucidated by a single-crystal X-ray diffraction. DFT calculations showed that the mechanism for the formal cycloaddition (CA) of N3− to trans-[PdCl(PH3)2(CNMe)]+ is stepwise. The process is both kinetically and thermodynamically favorable and occurs via the formation of an acyclic NNNCN-intermediate. The second step of the fo…
The Role of 1,3-Dipolar Cycloaddition Reactions in the Design and Synthesis of Complex Heterocyclic Scaffolds with Anti-tumor/Anti-infective Activity
2009
Polycyclic aromatic chains on metals and insulating layers by repetitive [3+2] cycloadditions
2020
The vast potential of organic materials for electronic, optoelectronic and spintronic devices entails substantial interest in the fabrication of π-conjugated systems with tailored functionality directly at insulating interfaces. On-surface fabrication of such materials on non-metal surfaces remains to be demonstrated with high yield and selectivity. Here we present the synthesis of polyaromatic chains on metallic substrates, insulating layers, and in the solid state. Scanning probe microscopy shows the formation of azaullazine repeating units on Au(111), Ag(111), and h-BN/Cu(111), stemming from intermolecular homo-coupling via cycloaddition reactions of CN-substituted polycyclic aromatic az…
Understanding the regioselectivity in hetero Diels–Alder reactions. An ELF analysis of the reaction between nitrosoethylene and 1-vinylpyrrolidine
2013
[EN] The regioselectivity in the hetero Diels-Alder reaction between nitrosoethylene 1 and 1-vinylpyrrolidine 2 has been studied by a comparative ELF bonding analysis along the IRC of the endo/ortho and endo/meta regioisomeric channels at the B3LYP/6-31G*. level. Along the most favorable endo/ortho regioisomeric channel, the C-C sigma bond is first formed by coupling of two pseudoradical centers located at the most electrophilic carbon of 1 and the most nucleophilic center of 2. Formation of these relevant pseudoradical centers, which depend on the total charge transfer process along the polar reaction, and not on the approach mode of each reagent, is well characterized by analysis of the a…
A DFT study of the role of Lewis acid catalysts in the mechanism of the 1,3-dipolar cycloaddition of nitrile imines towards electron-deficient acrylo…
2012
Abstract The role of the Mg complex formation in the reaction rate and regioselectivity of the 1,3-dipolar cycloaddition (13DC) reactions of nitrile imines (NIs) towards electron-deficient methacryloylpyrazolidinones has been theoretically studied using DFT methods at the B3LYP/6-31G * level. These 13DC reactions have an asynchronous concerted mechanism with a low polar character, displaying a high C regioselectivity induced by a steric repulsion between the phenyl substituent present at the C3 carbon of the NIs and the pyrazolidinone appendage present in the methacryloyl derivative, which increases with the formation of the bulky Mg–methacryloylpyrazolidinone complex. Solvent effect has be…
Design, Construction, and Characterization of a New Regioisomer and Diastereomer Material Based on the Spirooxindole Scaffold Incorporating a Sulphon…
2020
The 1,3-dipolar cycloaddition reaction is one of the most rapid, and efficient protocols to access, and construct highly divergent heterocycle chiral auxiliaries. Free catalyst synthesis of spirooxindole scaffold incorporating sulphone moiety via one pot&ndash
A DFT study of the Huisgen 1,3-dipolar cycloaddition between hindered thiocarbonyl ylides and tetracyanoethylene
2004
Abstract The mechanism for the 1,3-dipolar cycloaddition between the hindered thiocarbonyl ylide 1 and tetracyanoethylene 2 has been studied at the B3LYP/6-31G ∗ level. Formation of the [3+2] cycloadduct 4 takes place through a stepwise mechanism that is initiated by the nucleophilic attack of the thiocarbonyl ylide 1 to the ethylene derivative 2 to give a zwitterionic intermediate IN . The subsequent cyclization of IN yields a seven-membered cyclic ketene imine 6 , which equilibrates with the thermodynamically more stable [3+2] cycloadduct 4 . The computed free energies are in agreement with the experimental outcomes.
Bis-1,2,4-triazolo[4,3-a:3′,4′-c]quinoxalines of pharmaceutical interest from 1,3-dipolar cycloaddition
2008
Abstract Various derivatives of the heterocyclic system 1,12,12a,12b-tetrahydrobis-1,2,4-triazolo[4,3-a:3′,4′-c]quinoxaline of pharmaceutical interest have been obtained by double site- and regio-selective 1,3-dipolar cycloaddition of arylnitrilimines to quinoxalines. No evidence for the formation of mono-adducts was obtained, at variance with literature reports. Specific studies to establish the exact stereochemistry of the bis-cycloadducts were undertaken.