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1. Intramolecular proton transfer in the isomerization of hydroxyacetone: Characterization based on reaction force analysis and the bond fragility spectrum

   https://doi.org/10.1002/qua.26269  

   Joseph, Huiet V.; Derricotte, Wallace D. (June 2020, International Journal of Quantum Chemistry)

   Abstract The mechanism of isomerization of hydroxyacetone to 2‐hydroxypropanal is studied within the framework of reaction force analysis at the M06‐2X/6‐311++G(d,p) level of theory. Three unique pathways are considered: (a) a step‐wise mechanism that proceeds through the formation of the Z‐isomer of their shared enediol intermediate, (b) a step‐wise mechanism that forms the E‐isomer of the enediol, and (c) a concerted pathway that bypasses the enediol intermediate. Energy calculations show that the concerted pathway has the lowest activation energy barrier at 45.7 kcal mol⁻¹. The reaction force, chemical potential, and reaction electronic flux are calculated for each reaction to characterize electronic changes throughout the mechanism. The reaction force constant is calculated in order to investigate the synchronous/asynchronous nature of the concerted intramolecular proton transfers involved. Additional characterization of synchronicity is provided by calculating the bond fragility spectrum for each mechanism. 

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2. A Pyridine–Pyridine Cross‐Coupling Reaction via Dearomatized Radical Intermediates

   https://doi.org/10.1002/anie.201906267  

   Koniarczyk, J. Luke; Greenwood, Jacob W.; Alegre‐Requena, Juan V.; Paton, Robert S.; McNally, Andrew (September 2019, Angewandte Chemie International Edition)

   Abstract A pyridine–pyridine coupling reaction has been developed between pyridyl phosphonium salts and cyanopyridines using B₂pin₂as an electron‐transfer reagent. Complete regio‐ and cross‐selectivity are observed when forming a range of valuable 2,4′‐bipyridines. Phosphonium salts were found to be the only viable radical precursors in this process, and mechanistic studies indicate that the process does not proceed through a Minisci‐type coupling involving a pyridyl radical. Instead, a radical–radical coupling process between a boryl phosphonium pyridyl radical and a boryl‐stabilized cyanopyridine radical explains the C−C bond‐forming step. 

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3. Microwave Heating Outperforms Conventional Heating for a Thermal Reaction that Produces a Thermally Labile Product: Observations Consistent with Selective Microwave Heating

   https://doi.org/10.1002/asia.201900625  

   Duangkamol, Chuthamat; Batsomboon, Paratchata; Stiegman, Albert_E; Dudley, Gregory_B (June 2019, Chemistry – An Asian Journal)

   Abstract Microwave (MW) heating is more effective than conventional (CONV) heating for promoting a high‐temperature oxidative cycloisomerization reaction that was previously reported as a key step in a total synthesis of the natural product illudinine. The thermal reaction pathway as envisioned is an inverse electron‐demand dehydro‐Diels–Alder reaction with in situ oxidation to generate a substituted isoquinoline, which itself is unstable to the reaction conditions. Observed reaction yields were higher at a measured bulk temperature of 200 °C than at 180 °C or 220 °C; at 24 hours than at earlier or later time points; and when the reaction solution was heated using MW energy as opposed to CONV heating with a metal heat block. Selective MW heating of polar solute aggregates is postulated to explain these observations. 

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4. Chiral electrocatalysts eclipse water splitting metrics through spin control

   https://doi.org/10.1038/s41467-023-36703-w  

   Vadakkayil, Aravind; Clever, Caleb; Kunzler, Karli N.; Tan, Susheng; Bloom, Brian P.; Waldeck, David H. (February 2023, Nature Communications)

   Abstract Continual progress in technologies that rely on water splitting are often hampered by the slow kinetics associated with the oxygen evolution reaction (OER). Here, we show that the efficiency of top-performing catalysts can be improved, beyond typical thermodynamic considerations, through control over reaction intermediate spin alignment during electrolysis. Spin alignment is achieved using the chiral induced spin selectivity (CISS) effect and the improvement in OER manifests as an increase in Faradaic efficiency, decrease in reaction overpotential, and change in the rate determining step for chiral nanocatalysts over compositionally analogous achiral nanocatalysts. These studies illustrate that a defined spatial orientation of the nanocatalysts is not necessary to exhibit spin selectivity and therefore represent a viable platform for employing the transformative role of chirality in other reaction pathways and processes. 

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5. Palladium/Norbornene‐Catalyzed Direct Vicinal Di‐Carbo‐Functionalization of Indoles: Reaction Development and Mechanistic Study

   https://doi.org/10.1002/anie.202310697  

   Liu, Xin; Zhou, Yun; Qi, Xiaotian; Li, Renhe; Liu, Peng; Dong, Guangbin (September 2023, Angewandte Chemie International Edition)

   Abstract Methods that can simultaneously install multiple different functional groups to heteroarenes via C−H functionalizations are valuable for complex molecule synthesis, which, however, remain challenging to realize. Here we report the development of vicinal di‐carbo‐functionalization of indoles in a site‐ and regioselective manner, enabled by the palladium/norbornene (Pd/NBE) cooperative catalysis. The reaction is initiated by the Pd(II)‐mediated C3‐metalation and specifically promoted by the C1‐substituted NBEs. The mild, scalable, and robust reaction conditions allow for a good substrate scope and excellent functional group tolerance. The resulting C2‐arylated C3‐alkenylated indoles can be converted to diverse synthetically useful scaffolds. The combined experimental and computational mechanistic study reveals the unique role of the C1‐substituted NBE in accelerating the turnover‐limiting oxidative addition step. 

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