Cycloaddition of substituted allenes with 1,1-dichloro-2,2-difluoroethene. A model for the two-step, diradical-intermediate cycloaddition of allenes

Pasto, Daniel J.; Warren, Steven E.

doi:10.1021/ja00377a021

Cited by 18 publications

(4 citation statements)

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“…Pasto and coworkers showed that reactions of monoalkylallenes 26 and 555a , b with 542 (Scheme ) delivered E / Z stereoisomers 559 and 560 . In theory, either a concerted or diradical mechanism could be inferred from ratios of 559 / 560 .…”

Section: Allene Cyclization Involving Potential Diradical Intermediatesmentioning

confidence: 99%

“…The above results and reasoning in Scheme are used to infer if radicals are present in other [2 + 2] allene–alkene cycloadditions . For example, N -phenylmaleimide 563 (Scheme ), an electron-poor (LUMO controlled) reagent, could be envisaged to undergo a concerted reaction with the electron-rich olefin of allene 562 .…”

Section: Allene Cyclization Involving Potential Diradical Intermediatesmentioning

confidence: 99%

“…The above results and reasoning in Scheme 151 are used to infer if radicals are present in other [2 + 2] allene−alkene cycloadditions. 187 For example, N-phenylmaleimide 563 (Scheme 152), an electron-poor (LUMO controlled) reagent, could be envisaged to undergo a concerted reaction with the electron-rich olefin of allene 562. The reaction of 563 with allenes (24, 562a,b, R = CH 3 , CH 2 CH 3 , C(CH 3 ) 3 ) under thermal conditions 183 showed chemoselectivity consistent with either a concerted [ π 2 s + ( π 2 s + π 2 s )] or a stepwise diradical process.…”

Section: [2 + 2] Cycloadditionsmentioning

confidence: 99%

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Mechanistic Aspects and Synthetic Applications of Radical Additions to Allenes

2019

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More than 50 years have passed since Haszeldine reported the first addition of a trifluoromethyl radical to an allene; in the intervening years, both the chemistry of allenes and the reactivity of single-electron species have become topics of intense interest. In this Review, we provide an overview of the fundamentals of radical additions to allenes and highlight the emergence of theoretical and experimental evidence that reveals unique reactivity patterns for radical additions to allenes as compared with other unsaturated compounds. Factors capable of exerting control over the chemo-, regio-, and stereoselectivities of the attack of carbon-and heteroatom-based radicals at each of the three potential reactive sites in an allene substrate are described. These include reaction conditions, the nature of the attacking radical, the substitution pattern of the allene, and the length of the linker between the radical center and the proximal allene carbon in the substrate. Cycloaddition reactions between allenes and partners containing π-bonds, which are likely to proceed through radical pathways, are presented to highlight their ability to rapidly access complex polycyclic scaffolds. Finally, the synthetic utility of the products arising from these chemistries is described, including their applications to the construction of complex molecules.

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Section: Allene Cyclization Involving Potential Diradical Intermediatesmentioning

confidence: 99%

Section: Allene Cyclization Involving Potential Diradical Intermediatesmentioning

confidence: 99%

Section: [2 + 2] Cycloadditionsmentioning

confidence: 99%

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Mechanistic Aspects and Synthetic Applications of Radical Additions to Allenes

2019

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“…From this perspective, stereoelectronic and steric controlled reactivities of allenes and alkynes in these pericyclic reactions have been a subject of interest and their differential reactivities toward dienes are rather well established. − Allenes can undergo thermal Diels–Alder, 1,3-dipolar, and more interestingly thermal [2 + 2]-cycloaddition reactions. , In fact, intramolecular Diels–Alder reactions of allenes are one of most efficient synthetic approaches to produce small membered polynuclear isomers . Stepwise cyclizations of allene are capable of generating reactive intermediates, which diverge into different products via the same or different transition states. , These reactions are decoupled and show “Hidden-TSs”, which lead to branching in the potential energy surface .…”

Section: Introductionmentioning

confidence: 99%

Gold(I)-Catalyzed Intramolecular Diels–Alder Reaction: Evolution of Trappable Intermediates via Asynchronous Transition States

Mandal

Datta

2018

J. Org. Chem.

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In recent years allenes have been shown to be capable of exhibiting several modes of cycloadditions in the presence of transition metal catalysts that are otherwise unattainable for ethylene and acetylene. Herein, we predict that the [1 + 2]-cycloaddition pathway is accessible in a Au(I)-catalyzed reaction of allene with cis-1,3-butadiene. The electrophilicity of the central carbon of allene can be harnessed using a Au(I)-catalyst and -COOMe mediated stereoelectronics. A potential energy modification approach is applied to stabilize the diradicaloid intermediates. Our simulations establish that the product selectivity of the [4 + 2]- and [2 + 2]-pathways are steered by dynamical effects. Furthermore, a bioinspired version of this reaction is shown to afford an alternative synthetic pathway for proline and azepine analogs indicating rich prospects for thermal allene-butadiene reactions in drug discovery.

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