1,5-Dipolar cyclizations

Taylor, Edward C.; Turchi, Ignatius J.

doi:10.1021/cr60318a003

Cited by 205 publications

(53 citation statements)

References 107 publications

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“…Modern chemistry has benefited from the synthetic power and versatility of dipolar cycloaddition and cyclization reactions, [1][2][3][4] which have enabled far-reaching advances in many pursuits, from the preparation of unnatural β-amino acids, [5] to the kinetic resolution of stereoisomers, [6] to the functionalization of carbon nanotubes. [7] Alkyne-azide 1,3-dipolar cycloadditions are an especially practical subclass of reactions, given that molecules comprising terminal alkyne [8][9][10] and azide [11] functionalities are synthetically accessible and often commercially available.…”

Section: Introductionmentioning

confidence: 99%

Methylation of Ylidene‐Triazenes: Insight and Guidance for 1,3‐Dipolar Cycloaddition Reactions

et al. 2010

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Reaction of 1,3-dimesitylimidazolylidene (1) with p-functionalized phenyl azides 2 (a: H, b: OCH 3 , c: NO 2 ) afforded the respective imidazolylidene-triazenes 3 in good yields (65-99 %). Subsequent treatment with methyl iodide produced the corresponding methylated products 4 in near-quantitative yields (99 %). Analysis by NOESY 1D NMR spectroscopy and single-crystal X-ray diffraction revealed that the methylation reaction was regioselective and occurred at the nitrogen atom most distal from the heterocycle. Consistent with the formation of ionic salts, the 1 H NMR signals for the imidazole protons in 4 were shifted Ͼ 0.5 ppm downfield compared to 1, indicating the accumulation of positive charge.

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Section: Introductionmentioning

confidence: 99%

Methylation of Ylidene‐Triazenes: Insight and Guidance for 1,3‐Dipolar Cycloaddition Reactions

et al. 2010

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“…The pericyclic nature of this reaction has been amply debated, but only those of the very polar, ylid-like systems show evidence for reactive intermediates. [31] Again we focus only on activation and reaction energies. In this case, we chose sets of neutral molecules [Eqs.…”

mentioning

confidence: 99%

Improved Reaction and Activation Energies of [4+2] Cycloadditions, [3,3] Sigmatropic Rearrangements and Electrocyclizations with the Spin‐Component‐Scaled MP2 Method

Goumans

Ehlers

Lammertsma

et al. 2004

Chemistry A European J

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A new quantum mechanical scheme to calculate electronic correlation energies, spin-component-scaled MP2, was tested as a tool to predict reaction energies and barriers in computational organic chemistry. Three common pericyclic reactions with known unsatisfactory MP2 descriptions were reinvestigated with the modified MP2 approach, in which the parallel and anti-parallel spin components of the correlation energy are scaled separately. The SCS-MP2 calculated reaction and activation energies of nine Diels-Alder reactions, four [3,3] sigmatropic rearrangements, and ten electrocyclization reactions are compared to those of the MP2, B3 LYP, QCISD(T), and G3 methods. For each, the SCS-MP2 results are in excellent agreement with the experimental data and compare far more favorably to G3 than both MP2 and B3 LYP. Careful evaluation of the effect of the size of the atomic orbital (AO) basis set shows that the larger expansions improve the agreement with experiment for the SCS-MP2 method, while they get worse for both MP2 and B3 LYP.

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“…Formation of five-membered rings by 6π-electrocyclization is a well-precedented process in heterocyclic chemistry. [6][7][8][9][10] Several different synthetic approaches to alkenone carbenes have been developed over the years, producing intermediates that display common trends in their reactivity. [11][12][13][14][15][16][17] The utility of this cyclization approach to ring construction would be significantly expanded if the resulting bicyclic furan 2 was to undergo a subsequent [4+2]-cycloaddition, since a cyclohexane annulation would then result (i.e., 2→4→5).…”

Section: Introductionmentioning

confidence: 99%

Intramolecular cycloaddition reaction of bromo and nitro substituted furanyl amides

Padwa¹,

Crawford²,

Straub³

2006

Arkivoc

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Dedicated to Waldemar Adam on the occasion of his 70th anniversary AbstractThe intramolecular Diels-Alder reaction (IMDAF) of an N-alkenyl substituted furanyl amide was investigated. Upon thermolysis at 80-110 o C, a smooth IMDAF reaction occurred to provide a stable aza-7-oxabicyclo[2.2.1]heptane cycloadduct in high yield. The intramolecular cyclization of the related 5-bromo substituted furanyl amide was found to proceed at a much faster rate and in higher yield than the unsubstituted variant. The rate enhancement observed by incorporating a bromine in the 5-position of the furan ring appears to be general. The origin of the increased rate of cycloaddition for the 5-bromo substituted furan when compared to the unsubstituted example can be attributed to an increase in reaction exothermicity; this both decreases the activation enthalpy, and increases the barrier to retrocycloaddition. Bromine substitution on furan also increases reactant energy and stabilizes the product due to the preference of the electronegative bromine atom to be attached to a more highly alkylated, and therefore more electropositive framework. An unusual isomerization-cyclization reaction of a 5-nitro substituted furanyl amide was also found to occur under microwave conditions and provided a 1,4-dihydro-2H-benzo[4.5]furo[2,3-c]pyridin-3-one derivative.

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1,5-Dipolar cyclizations

Cited by 205 publications

References 107 publications

Methylation of Ylidene‐Triazenes: Insight and Guidance for 1,3‐Dipolar Cycloaddition Reactions

Methylation of Ylidene‐Triazenes: Insight and Guidance for 1,3‐Dipolar Cycloaddition Reactions

Improved Reaction and Activation Energies of [4+2] Cycloadditions, [3,3] Sigmatropic Rearrangements and Electrocyclizations with the Spin‐Component‐Scaled MP2 Method

Intramolecular cycloaddition reaction of bromo and nitro substituted furanyl amides

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