Hydrogen Migration Over Organic Tapes: [1,5] Sigmatropic Shiftamers

Tantillo, Dean J.; Hoffmann, Roald

doi:10.1002/ejoc.200300583

Cited by 8 publications

(15 citation statements)

References 29 publications

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“…More than a century since the first report of sigmatropic rearrangements in 1912, only 11 studies have explored them in the context of polymers. − Five of these studies are theoretical: Roald Hoffmann and co-workers investigated intriguing hypothetical classes of polymers they called “sigmatropic shiftamers,” because they predicted sigmatropic shiftseither Cope rearrangements or [1, n ]-hydride shiftswould render the polymer fluxional along its entire backbone. − The other six studies were experimental and utilized (orthoester-)Claisen rearrangements for peripheral modification of polyaramids and polyimides − or the surface of graphene oxide, or diaza-Cope rearrangement to mediate step-growth polymerization of diamines and dialdehydes . Lastly, formally sigmatropic 1,2-Brook rearrangements were recently utilized to do skeletal editing of polymer chains. , Though scarce, these precedents provide a sound framework for further advances.…”

Section: Introductionmentioning

confidence: 99%

Sigmatropic Rearrangements of Polymer Backbones: Vinyl Polymers from Polyesters in One Step

Ditzler

Zhukhovitskiy

2021

J. Am. Chem. Soc.

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Polymer modification is a fundamental scientific challenge, as a means of both upcycling plastics and extracting a stimulus response from them. To date, the overwhelming majority of polymer modifications has focused on the polymer periphery. Herein, we demonstrate nearly quantitative, scission-free modification of polymer backbones, namely, a metamorphosis of polyesters into vinyl polymers resembling commodity materials via the Ireland–Claisen sigmatropic rearrangement. The glass transition temperature (T g) and thermal stability of the polyesters undergo dramatic changes post-transformation. Beyond polymer modification, our work advances the application of retrosynthetic analysis in polymer synthesis; the nontraditional production of vinyl polymers from lactones opens the door to a slew of previously inaccessible materials.

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Section: Introductionmentioning

confidence: 99%

Sigmatropic Rearrangements of Polymer Backbones: Vinyl Polymers from Polyesters in One Step

Ditzler

Zhukhovitskiy

2021

J. Am. Chem. Soc.

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“…Suprafacial hydrogen shifts can also be incorporated into sigmatropic shiftamer architectures. 15 The transition structure for the parent [1,5] H shift is shown in Figure 8. Because of the orbital symmetry requirement 14 that a [1,5] H shift be suprafacial, shiftamers based on open-chain polyenes are not geometrically feasible.…”

Section: The Snakes: [1n] Shiftamersmentioning

confidence: 99%

“…Shiftamers constructed from polycyclic conjugated π systems 16 were therefore explored. 15 In these systems, hydrogen atoms migrate over the faces of organic "tapes" (Chart 4). Unfortunately, the barriers computed on the basis of model systems tend to be quite high.…”

Section: The Snakes: [1n] Shiftamersmentioning

confidence: 99%

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Snakes and Ladders. The Sigmatropic Shiftamer Concept

Tantillo

Hoffmann

2006

Acc. Chem. Res.

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“…Tantillo and Hoffmann describe potential [1,5] sigmatropic shiftamers in which suprafacial hydrogen atom migration might propagate along an infinite tape of monohydro polycyclic aromatic hydrocarbons. 53 An example of an allowed shift in a polyphenacene is shown in Scheme 13. Other systems considered are polyazulenes and polypentalenes.…”

Section: [15] Sigmatropic Rearrangementsmentioning

confidence: 99%

11 Reaction mechanisms : Part (iii) Pericyclic reactions

Morgan

2005

Annu. Rep. Prog. Chem., Sect. B

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This review is a collection of the highlights in the field of pericyclic reactions published in the year 2004. Research in this fascinating topic continues to be centred on the understanding of the mechanisms of the three major classes of pericyclic reactions: cycloaddition reactions, electrocyclic reactions, and sigmatropic rearrangements, as well as into those of more unusual pseudopericyclic processes. HighlightsThese featured papers published in 2004 involve fundamental questions in pericyclic reaction mechanisms. Baldwin and co-workers studied the forbidden disrotatory 4-electron ring opening of cis-bicyclo[4.2.0]oct-7-ene, and using secondary kinetic isotope effect measurements the authors conclude that the rearrangement occurs through a concerted disrotatory process; conrotation almost certainly occurs, but the strained product reverts to the reactant. 1,2 Doering et al. studied the sigmatropic [1,5] hydrogen migration in phenyl-substituted 1,3-pentadienes to determine whether this reaction, like the Cope rearrangement, has a chameleonic transition state, dependent on the position and nature of substituents. 3 Although substituent effects are small, the authors conclude that the results are consistent with the chameleonic transition state. Calculations of the same reaction were reported by Borden and co-workers and also show small substituent effects; also there are few structural differences between the contributing structures of the transition state but large energy differences. 4 Although the computational data do not support a chameleonic transition state, perhaps a different [1,5] rearrangement might. Gajewski published a second, updated edition of ''Hydrocarbon Thermal Isomerizations'', which includes many pericyclic rearrangements. 5 Two computational benchmarking studies of pericyclic reactions were published. Houk, Pulay and co-workers compared the use of the Handy/Cohen OLYP and O3LYP functionals in pericyclic reactions to B3LYP and CBS-QB3 methods. 6 Although the OLYP functional was found in a previous benchmarking study to be superior to BLYP in predicting thermochemistry and molecular geometry, it is comparable to BLYP for pericyclic reactions and O3LYP is comparable to B3LYP. Also, in a collaborative effort, Goumans et al. presented a new computational method for the inclusion of electron correlation. 7 This spin-component-scaled MP2 (SCS-MP2) method was tested on a variety of Diels-Alder reactions, [3,3] sigmatropic rearrangements and electrocyclic reactions, cases in which MP2 calculations fail. The results are in excellent agreement with experiment, are closer to G3 values than MP2 or B3LYP, and the results improve with the basis set size, unlike MP2 and B3LYP.

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Hydrogen Migration Over Organic Tapes: [1,5] Sigmatropic Shiftamers

Abstract: We explore the possibility of suprafacial hydrogen atom migration over several organic tapes-infinite chains of polycyclic conjugated hydrocarbons. It's not easy.

Cited by 8 publications

References 29 publications

Sigmatropic Rearrangements of Polymer Backbones: Vinyl Polymers from Polyesters in One Step

Sigmatropic Rearrangements of Polymer Backbones: Vinyl Polymers from Polyesters in One Step

Snakes and Ladders. The Sigmatropic Shiftamer Concept

11 Reaction mechanisms : Part (iii) Pericyclic reactions

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