Mechanism of 1,3-dipolar cycloadditions

Firestone, Raymond A.

doi:10.1021/jo01270a023

Cited by 298 publications

(176 citation statements)

References 5 publications

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“…This conclusion supports the concept of the radical character of '1,3-dipolar cycloaddition reactions' formulated by Firestone [11], at least for some systems with the required structural features.…”

Section: Formulae 6a and 6bsupporting

confidence: 86%

Studies on the Reactions of Thiocarbonyl S‐Methanides with Hetaryl Thioketones

Mlostoń

Pipiak

Linden

et al. 2015

Helvetica Chimica Acta

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Dihetaryl thioketones react with thiocarbonyl ylides to give 1,3-dithiolanes in high yields. No competitive side reactions of the thiocarbonyl ylides were observed, evidencing the 'superdipolarophilic' character of this less-known group of thioketones. Depending on the type of substituents present in both the thiocarbonyl ylide and the thioketone, formal [3+2] cycloadditions occur with complete regioselectivity or with formation of a mixture of both regioisomers. Regioselective formation of the sterically more crowded 1,3-dithiolanes is explained via a mechanism involving stabilized 1,5-biradicals. In systems with less-efficient radical stabilization, e.g., in the case of adamantanethione S-methanide, substantial violation of the regioselectivity was observed as a result of steric hindrance.

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Section: Formulae 6a and 6bsupporting

confidence: 86%

Studies on the Reactions of Thiocarbonyl S‐Methanides with Hetaryl Thioketones

Mlostoń

Pipiak

Linden

et al. 2015

Helvetica Chimica Acta

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“…This mechanism has also been postulated recently by Goddard and Walch (1 8). It does not involve a reorganization of the atomic formal charge distribution as the reaction proceeds, and therefore it is compatible with the observed lack of solvent dependency on the rate of cycloaddition (37,39).…”

Section: ( a ) Ozone And Nitritesupporting

confidence: 66%

“…Both calculations locate a small formal positive charge on the terminal nitrogen atom, and rather larger negative and positive 'Firestone has formulated mechanism (c) as a two-step mechanism (39). See ref.…”

Section: ( a ) Ozone And Nitritementioning

confidence: 98%

Valence-bond studies of 4-electron 3-centre bonding units. I. The π-electrons of O₃, NO₂⁻, and CH₂N₂

Harcourt¹,

Roso²

1978

Can. J. Chem.

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ROSO. Can. J. Chem. 56,1093 (1978. Some nb-i~lirio valence-bond wave-functions are reported for the n-electrons of the groundstates of 0 3 , NOz-, and CHzNz. Examination of these wave-functions provides further support for the hypothesis that, for the ground-states of many electron-excess molecules, important valence-bond structures are those that are compatible with the electroneutrality principle, i.e. they carry either small or zero formal charges on each of the atoms. For O3 and CHzNz, the important valence-bond structures with zero atomic formal charges are Each of these structures has a 'long-bond' between non-adjacent atoms. The significance of 'long-bond' (or spin-paired diradical) structures for the electronic mechanism of 1,3-dipolar cycloaddition reactions is discussed and 'increased-valence' descriptions of the electronic structure of each molecule are presented. Some comments on the utility of 'increased-valence' structures are provided. [Traduit par le journal]

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“…-The concertedness of 1,3-dipolar cycloaddition reactions is an important feature of these processes with great importance for synthetic applications and for the theory of organic reactions [1]. The alternative stepwise mechanisms via a diradical or a zwitterionic intermediate were also postulated [2] [3]. In the case of electron-rich 1,3-dipoles like thiocarbonyl S-methanides, reactions with electron-deficient dipolarophiles bearing CF 3 , CN, and CO 2 R groups, respectively, were shown to proceed via zwitterionic intermediates [4a][4b].…”

mentioning

confidence: 99%

Concerted vs. Non‐Concerted 1,3‐Dipolar Cycloadditions of Azomethine Ylides to Electron‐Deficient Dialkyl 2,3‐Dicyanobut‐2‐enedioates

Khlebnikov

Konev

Virtsev

et al. 2014

Helvetica Chimica Acta

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The quantum-chemical calculations of the thermal ring opening of 1-methyl-2,3-diphenyl-and 1,2,3-triphenylaziridine with formation of the corresponding azomethine ylides of S-, U-, and W-type as well as their cycloaddition to dimethyl acetylenedicarboxylate (DMAD) and dimethyl 2,3-dicyanobut-2-enedioate, were performed at the DFT B3LYP/6-31G(d) level of theory with the PCM solvation model. The calculations are in complete accordance with experimental results and explain the switch from the concerted to the non-concerted pathway depending on substituents in the dipolarophile and the ylide. It was found that strong electron-withdrawing substituents in dipolarophiles, such as in dialkyl dicyanobutenedioates, significantly reduce the barrier for the formation of zwitterionic intermediates in the reaction of azomethine ylides with such dipoles. This can render the stepwise cycloaddition competitive with the concerted one. However, the concertedness of the cycloaddition even to dipolarophiles with several electron-withdrawing substituents is governed by a fine balance of electronic and steric effects in both ylide and dipolarophile counterparts. The hypothesis that introduction of substituents in the azomethine ylide that destabilize the positive charge in a corresponding zwitterion will favor the concerted cycloaddition even with dialkyl dicyanobutenedioates was tested theoretically and experimentally.

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Mechanism of 1,3-dipolar cycloadditions

Cited by 298 publications

References 5 publications

Studies on the Reactions of Thiocarbonyl S‐Methanides with Hetaryl Thioketones

Studies on the Reactions of Thiocarbonyl S‐Methanides with Hetaryl Thioketones

Valence-bond studies of 4-electron 3-centre bonding units. I. The π-electrons of O₃, NO₂⁻, and CH₂N₂

Concerted vs. Non‐Concerted 1,3‐Dipolar Cycloadditions of Azomethine Ylides to Electron‐Deficient Dialkyl 2,3‐Dicyanobut‐2‐enedioates

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Mechanism of 1,3-dipolar cycloadditions

Cited by 298 publications

References 5 publications

Studies on the Reactions of Thiocarbonyl S‐Methanides with Hetaryl Thioketones

Studies on the Reactions of Thiocarbonyl S‐Methanides with Hetaryl Thioketones

Valence-bond studies of 4-electron 3-centre bonding units. I. The π-electrons of O3, NO2−, and CH2N2

Concerted vs. Non‐Concerted 1,3‐Dipolar Cycloadditions of Azomethine Ylides to Electron‐Deficient Dialkyl 2,3‐Dicyanobut‐2‐enedioates

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Valence-bond studies of 4-electron 3-centre bonding units. I. The π-electrons of O₃, NO₂⁻, and CH₂N₂