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1. Mechanistic studies of a “Declick” reaction

   https://doi.org/10.1039/c9sc00690g  

   Meadows, Margaret K.; Sun, Xiaolong; Kolesnichenko, Igor V.; Hinson, Caroline M.; Johnson, Kenneth A.; Anslyn, Eric V. (October 2019, Chemical Science)

   A kinetic analysis of a “declick” reaction is described. Compound 1 , previously reported to couple an amine and a thiol ( i.e. “click”) under mild aqueous conditions to create 2 , undergoes release of the unaltered coupling partners upon triggering with dithiothreitol ( DTT ). In the study reported herein various aniline derivatives possessing para-electron donating and withdrawing groups were used as the amines. UV/vis spectroscopy of the declick reaction shows time-dependent spectra lacking isosbestic points, implying a multi-step mechanism. Global data fitting using numerical integration of rate equations and singular value decomposition afforded the spectra and time-dependence of each species, as well as rate constants for each step. The kinetic analysis reveals a multi-step process with an intermediate where both thiols of DTT have added prior to expulsion of the aniline leaving group, followed by rearrangement to the final product. Hammett plots show a negative rho value on two of the steps, indicating positive charge building ( i.e. reduction of a negative charge) in the step leading to the intermediate and its rate-determining breakdown. Overall, the kinetic study reported herein gives a complete mechanistic picture of the declick reaction. 

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2. A grain boundary model of metamorphic reaction

   https://doi.org/10.1007/s00410-024-02100-9  

   Spear, Frank S. (March 2024, Contributions to Mineralogy and Petrology)

   Abstract A model is presented whereby metamorphic parageneses are governed by local, nano-scale reactions among adjacent phases along grain boundaries that are driven by local disequilibrium between the solid phases and the grain boundary composition. These reactions modify the grain boundary composition setting up compositional gradients that drive diffusion and change the grain boundary composition elsewhere in the rock, which drive local reactions in these locations. The process may be triggered by the nucleation of a new phase that is out of equilibrium with the existing assemblage and an example is presented based on the transformation of kyanite (Ky) to sillimanite (Sil). Model results reveal that a simple polymorphic transformation (Ky→Sil) can result in local reactions among all phases in the rock and some phases may grow in one locale and be consumed in another. An implication of these results is that interpretation of metamorphic parageneses based on growth or resorption and compositional changes of phases requires careful evaluation of nano-scale processes. 

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3. Mechanistic Investigation of a Photoredox Cycloaddition Chain Reaction

   https://doi.org/10.1021/jacs.4c14255  

   Lee, Annemarie A; Swierk, John R (December 2024, Journal of the American Chemical Society)
4. Total Synthesis of Clerobungin A via a Cascade Cyclization Reaction

   https://doi.org/10.1021/acs.joc.6b02261  

   Mease, James; Reber, Keith P. (November 2016, The Journal of Organic Chemistry)
5. Microwave-specific acceleration of a retro-Diels–Alder reaction

   https://doi.org/10.1039/d0cc04584e  

   Frasso, Michael A.; Stiegman, Albert E.; Dudley, Gregory B. (September 2020, Chemical Communications)

   A high-temperature retro-Diels–Alder reaction is accelerated by microwave (MW) heating to rates higher than expected based on Arrhenius kinetics and the measured temperature of the reaction mixture. Observations are consistent with selective MW heating of the polar reactant relative to other, less polar components of the reaction mixture. 

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