Bicyclo[3.2.0]heptane Mechanophores for the Non-scissile and Photochemically Reversible Generation of Reactive Bis-enones

Kean, Zachary S.; Ramirez, Ashley L. Black; Yan, Yufan; Craig, Stephen L.

doi:10.1021/ja3063666

Cited by 61 publications

(52 citation statements)

References 29 publications

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“…The ringopening mechanophore with the largest known elongation, at 0.4 nm, is a bicyclo [3.2.0]heptane. [9] Herein, we report the synthesis of a ring-opening mechanophore with an elongation of more than 1.0 nm. The elongation was directly measured by single-molecule force spectroscopy (SMFS) [10,[11][12][13][14] and compared to quantum chemical calculations.…”

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confidence: 99%

Pinpointing Mechanochemical Bond Rupture by Embedding the Mechanophore into a Macrocycle

et al. 2015

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Mechanophores contain a mechanically labile bond that can be broken by an external mechanical force. Quantitative measurement and control of the applied force is possible through atomic force microscopy (AFM). A macrocycle was synthesized that contains both the mechanophore and an aliphatic chain that acts as a "safety line" upon bond breaking. This ring-opening mechanophore unit is linked to poly(ethylene glycol) spacers, which allow investigation by single molecule force spectroscopy. The length increase upon rupture of the mechanophore was measured and compared with quantum chemical calculations.

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confidence: 99%

Pinpointing Mechanochemical Bond Rupture by Embedding the Mechanophore into a Macrocycle

et al. 2015

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“…Previous efforts have demonstrated a photoreversible, single mechanophore system embedded in poly(methyl acrylate). 32 Here, we expand the non-scissile mechanophore repertoire by incorporating bicyclo[4.2.0]octane (BCO) functionality into high molecular weight (MW) polyesters via carbodiimide polyesterification 33 of BCO containing diester diols. We also use the BCO platform to analyze stereochemical effects on mechanochemical reactivity, for potential self-healing applications via stress-generated α,β-unsaturated ester functional groups, and as a tool for mechanistic inquiry through analysis of stereochemical product distributions.…”

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confidence: 99%

Stress-Responsive Polymers Containing Cyclobutane Core Mechanophores: Reactivity and Mechanistic Insights

et al. 2013

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A primary goal of covalent mechanochemistry is to develop polymer bound mechanophores that undergo constructive transformations in response to otherwise destructive forces. The [2+2] cycloreversion of cyclobutane mechanophores has emerged as a versatile framework to develop a wide range of stress-activated functionality. Herein, we report the development of a class of cyclobutane bearing bicyclo[4.2.0]octane mechanophores. Using carbodiimide polyesterification, these stress-responsive units were incorporated into high molecular weight polymers containing up to 700 mechanophores per polymer chain. Under exposure to the otherwise destructive elongational forces of pulsed ultrasound, these mechanophores unravel by ~7 Å per monomer unit to form α,β-unsaturated esters that react constructively via thiol-ene conjugate addition to form sulfide functionalized copolymers and cross-linked polymer networks. To probe the dynamics of the mechanochemical ring opening, a series of bicyclo[4.2.0]octane derivatives that varied in stereochemistry, substitution, and symmetry were synthesized and activated. Reactivity and product stereochemistry was analyzed by 1H NMR, which allowed us to interrogate the mechanism of the mechanochemical [2+2] cycloreversion. These results support that the ring opening is not concerted, but proceeds via a 1,4 diradical intermediate. The bicyclo[4.2.0]octanes hold promise as active functional groups in new classes of stress-responsive polymeric materials.

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“…Pericyclic transformations form a major part of the mechanochemistry canon, with examples ranging from electrocyclic ring-openings of benzocyclobutenes [4] and gem-dihalocyclopropanes (gDHCs) [8] to cycloreversions of Diels-Alder adducts [9], cyclobutanes [10] and dioxetanes [11]. Two of the most practicable, real-time reporters of mechanical stress in polymeric materials to have emerged from the mechanochemistry field fall into this broad class of mechanically-induced transformations.…”

Section: Spiropyran Mechanochromismmentioning

confidence: 99%

“…9). Finally, two detailed studies on bicyclo[3.2.0]-heptanes emerged from the Craig group in 2013 and 2014 [10,54] (Fig. 10).…”

Section: Mechanically-induced Bond Creationmentioning

confidence: 99%

Mechanochemical Reactions Reporting and Repairing Bond Scission in Polymers

Clough

Balan

Sijbesma

2015

Topics in Current Chemistry

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The past 10 years have seen a resurgence of interest in the field of polymer mechanochemistry. Whilst the destructive effects of mechanical force on polymer chains have been known for decades, it was only recently that researchers tapped into these forces to realize more useful chemical transformations. The current review discusses the strategic incorporation of weak covalent bonds in polymers to create materials with stress-sensing and damage-repairing properties. Firstly, the development of mechanochromism and mechanoluminescence as stress reporters is considered. The second half focuses on the net formation of covalent bonds as a response to mechanical force, via mechanocatalysis and mechanically unmasked chemical reactivity, and concludes with perspectives for the field.

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Bicyclo[3.2.0]heptane Mechanophores for the Non-scissile and Photochemically Reversible Generation of Reactive Bis-enones

Cited by 61 publications

References 29 publications

Pinpointing Mechanochemical Bond Rupture by Embedding the Mechanophore into a Macrocycle

Pinpointing Mechanochemical Bond Rupture by Embedding the Mechanophore into a Macrocycle

Stress-Responsive Polymers Containing Cyclobutane Core Mechanophores: Reactivity and Mechanistic Insights

Mechanochemical Reactions Reporting and Repairing Bond Scission in Polymers

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