Cycloadducts of nitrones with isocyanates; 1,2,4- or 1,3,4-oxadiazolidinones?

Bell, Anthony M. T.; Bridges, J.; Cross, Rebecca; Falshaw, C. P.; Taylor, Brian F.; Taylor, Giles A.; Whittaker, Ian; Begley, Michael J.

doi:10.1039/p19870002593

Cited by 12 publications

(6 citation statements)

References 1 publication

(1 reference statement)

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“…Experimentally, the reaction is usually carried out in less polar solvents such as toluene, , dichloromethane, ,, and chloroform; , there only is one report in which the reaction is reported to be performed in acetonitrile . In order to better appreciate the solvent effect we also evaluate the reaction between 1a and 2a in additional solvents, i.e., hexane, toluene, chloroform, and acetonitrile.…”

Section: Resultsmentioning

confidence: 99%

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Revealing Stepwise Mechanisms in Dipolar Cycloaddition Reactions: Computational Study of the Reaction between Nitrones and Isocyanates

et al. 2015

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The mechanism of cycloaddition reactions of nitrones with isocyanates has been studied using density functional theory (DFT) methods at the M06-2X/cc-pVTZ level of theory. The exploration of the potential energy surfaces associated with two reactive channels leading to 1,2,4-oxadiazolidin-5-ones and 1,4,2-dioxazolidines revealed that the cycloaddition reaction takes place through a concerted mechanism in gas phase and in apolar solvents but a stepwise mechanism in polar solvents. In stepwise mechanisms, the first step of the reaction is a rare case in which the nitrone oxygen acts as a nucleophile by attacking the central carbon atom of the isocyanate (interacting with the π-system of the C═O bond) to give an intermediate. The corresponding transition structure is stabilized by an attractive electrostatic interaction favored in a polar medium. The second step of the reaction is the rate-limiting one in which the formation of 1,2,4-oxadiazolidin-5-ones or 1,4,2-dioxazolidines is decided. Calculations indicate that formation of 1,2,4-oxadiazolidin-5-ones is favored both kinetically and thermodynamically independently of the solvent, in agreement with experimental observations. Noncovalent interactions (NCI) and topological analysis of the gradient field of electron localization function (ELF) bonding confirmed the observed interactions.

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Section: Resultsmentioning

confidence: 99%

“…Depending on the type of compound one or both double bonds of the allene can participate in the cycloaddition reaction. In the reaction of nitrones with isocyanates, both the CN and CO bonds of the isocyanate can act as dipolarophiles to give 1,2,4-oxadiazolidin-5-ones 3 and 1,4,2-dioxazolidines 4 , respectively (Scheme ).…”

Section: Introductionmentioning

confidence: 99%

Revealing Stepwise Mechanisms in Dipolar Cycloaddition Reactions: Computational Study of the Reaction between Nitrones and Isocyanates

et al. 2015

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“…Although examples of 2-substituted-1,2,4-oxadiazolidin-5-ones and -thiones [3][4][5][6] and tetrahydroimidazo [1,5-b] [1,2,4]oxadiazol-2(1H)-ones [7,8] and thiones [9,10] are known in the literature, examples of 2-unsubstituted-1,2,4-oxadiazolidin-5-ones are absent. Lycoposerramine-A, is a recently reported alkaloid which has a 4-unsubstituted-1,2,4-oxadiazolidin-5-one residue in the molecule [11].…”

Section: Introductionmentioning

confidence: 98%

Supramolecular architecture of phenylcarbamoylated acetone oxime 1,1-diisopropyl-3-phenylurea] complex

et al. 2006

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Carbamoylated oximes 1 form 1:1 molecular complexes 4 with N,N-dialkyl-N -phenylurea when stirred in THF or ether at room temperature for short time in good yields. The molecular complexes 4a-e were isolated and characterized by analytical and spectral means. X-ray crystallographic analysis for complex 4a was performed. In this paper, we report the use of complex 4a and its moieties as building blocks to form non-interacting polymeric zigzag chains by inter-and intramolecular hydrogen bonds along baxis, and details of supramolecular architecture of 4a. There is a intramolecular H-H interaction between hydrogen of urea NH and neighboring hydrogen of diisopropyl's CH linked to the other urea nitrogen. In addition, to obtain the most favorable orientation of the moieties of the title complex, PM3 semi-empirical quantum mechanical calculations were performed and then results from X-ray crystallography and computational modeling were compared.

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“…This is in good agreement with the data reported in the literature. [6] Compounds 2a-f underwent a retro cycloaddition reaction when heated under vacuum. The formed nitrones were isolated and compared with authentic samples (see Table 1).…”

Section: Introductionmentioning

confidence: 99%

Cycloaddition of Acyclic Nitrones with Phenyl Isocyanate: Synthesis and Ring‐Opening Reactions of 1,2,4‐Oxadiazolidin‐5‐ones

Coşkun

Parlar

2006

Synthetic Communications

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The cycloaddition of nitrones with unsubstituted or electron-donating substituents on the C-phenyl 1a,c,f with phenyl isocyanate proceeds smoothly for a short time with high yields to give the corresponding 1,2,4-oxadiazolidinone 2, and 1b,d,e with electron-withdrawing substituents gave the corresponding oxadiazolidinone in moderate yields after prolonged heating. Oxadiazolidinones 2a,c,f undergo diethylamine-induced fragmentation for a short time to give the corresponding Schiff bases, and oxadiazolidinones 2b,d,e remain unchanged in these conditions. Prolonged heating of 2d,e in the presence of diethylamine led to complex mixtures. In the case of 2b the corresponding amidine was the main product of the reaction.

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Cycloadducts of nitrones with isocyanates; 1,2,4- or 1,3,4-oxadiazolidinones?

Cited by 12 publications

References 1 publication

Revealing Stepwise Mechanisms in Dipolar Cycloaddition Reactions: Computational Study of the Reaction between Nitrones and Isocyanates

Revealing Stepwise Mechanisms in Dipolar Cycloaddition Reactions: Computational Study of the Reaction between Nitrones and Isocyanates

Supramolecular architecture of phenylcarbamoylated acetone oxime 1,1-diisopropyl-3-phenylurea] complex

Cycloaddition of Acyclic Nitrones with Phenyl Isocyanate: Synthesis and Ring‐Opening Reactions of 1,2,4‐Oxadiazolidin‐5‐ones

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