Preparation and Characterization of a Small Library of Thermally-Labile End-Caps for Variable-Temperature Triggering of Self-Immolative Polymers

Abstract

The reaction between furans and maleimides has increasingly become a method of interest as its reversibility makes it a useful tool for applications ranging from self-healing materials, to self-immolative polymers, to hydrogels for cell culture and for the preparation of bone repair. However, most of these applications have relied on simple monosubstituted furans and simple maleimides and have not extensively evaluated the potential thermal variability inherent in the process that is achievable through simple substrate modification. A small library of cycloadducts suitable for the above applications was prepared, and the temperature dependence of the retro-Diels-Alder processes was determined through in situ H NMR analyses complemented by computational calculations. The practical range of the reported systems ranges from 40 to>110 °C. The cycloreversion reactions are more complex than would be expected based on simple trends expected based on frontier molecular orbital analyses of the materials.

Electrocatalytic Depolymerization of Self-Immolative Poly(Dithiothreitol) Derivatives

“…The depolymerization products can, for some polymers, be recovered as small monomer-like compounds from which the monomer can be regenerated and used for the synthesis of pristine polymer materials [ 3 ]. A comprehensive review was published by Gillies and coworkers in 2019 discussing applications and various triggering stimuli [ 2 ], e.g., UV–Vis [ 4 ], fluoride [ 5 , 6 , 7 , 8 ], heat [ 9 ], bovine serum albumin [ 10 ], acid [ 11 , 12 ], palladium [ 6 , 7 , 8 ], base [ 7 ], and H 2 O 2 [ 13 ], among others. Phillips and coworkers developed a system comprising poly(benzyl carbamate), which depolymerized in response to metal ions, i.e., Hg 2+ and Pb 2+ [ 14 ].…”

Targeting Valuable Chemical Commodities: Hydrazine‐mediated Diels‐Alder Aromatization of Biobased Furfurals

“…[ 20 , 24 , 51 , 52 ] 5‐HMF‐derived hydrazone and its ethyl ether analogue afforded disappointing yields, again due to competitive degradation side reactions (entries 3 and 4). Presumably, the presence of a leaving group in the structure of furans 1 c and 1 d contributes to the increased chemical lability of these hydrazones, [53] according to the mechanism proposed in Scheme 2 . This suggestion is supported by the ionization behavior of 1 c and 1 d seen in electron spray ionization mass spectrometry (ESI‐MS) characterization, which shows expulsion of the leaving group (HO − and EtO − , respectively, see Supporting Information for details).…”

Incorporation of a Tethered Alcohol Enables Efficient Mechanically Triggered Release in Aprotic Environments

“…In 2019, our group introduced a platform for mechanically triggered molecular release based on an unstable furfuryl carbonate masked as a mechanochemically active Diels–Alder adduct (Scheme a) . This general design strategy relies on the decomposition of a latent 2-furylcarbinol derivative, , which is gated by a mechanochemical retro-Diels–Alder reaction. Decoupling the mechanochemical activation step from 2-furylcarbinol decomposition provides for a highly modular system that we have further developed to enable the mechanically triggered release of functionally diverse molecular payloads including alcohols, amines, carboxylic acids, and sulfonic acids. , Notably, a polar protic environment is typically required for clean and efficient fragmentation of the latent 2-furylcarbinol derivative, which decomposes via a putative furfuryl cation intermediate.…”