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α‐Carbonyl cations are the umpolung forms of the synthetically fundamental α‐carbonyl carbanions. They are highly reactive yet rarely studied and utilized species and their precursors were rather limited. Herein, we report the catalyst‐controlled divergent generations of α‐carbonyl cations from single alkyne functionalities and the interception of them via Wagner–Meerwein rearrangement. Two chemodivergent catalytic systems have been established, leading to two different types of α‐carbonyl cations and, eventually, two different types of products, i.e. the α,β‐ and β,γ‐unsaturated carbonyl compounds. Broad spectrum of alkynes including aryl alkyne, ynamide, alkynyl ether, and alkynyl sulfide could be utilized and the migration priorities of different groups in the Wagner–Meerwein rearrangement step was elucidated. Density functional theory calculations further supported the intermediacy of α‐carbonyl cations via the N−O bond cleavage in both the two catalytic systems. Another key feature of this methodology was the fragmentation of synthetically inert tert‐butyl groups into readily transformable olefin functionalities. The synthetic potential was highlighted by the scale‐up reactions and the downstream diversifications including the formal synthesis of nicotlactone B and galbacin. [ABSTRACT FROM AUTHOR]

Palladium (Pd)‐catalyzed radical oxidative C−H carbonylation of alkanes is a useful method for functionalizing hydrocarbons, but there is still a lack of understanding of the mechanism, which restricts the application of this reaction. In this work, density functional theory (DFT) calculations were carried out to study the mechanism for a Pd‐catalyzed radical esterification reaction. Two plausible reaction pathways have been proposed and validated by DFT calculations. The computational results reveal that the generated alkyl radical prefers to add to the carbon monoxide (CO) molecule to form a carbonyl radical before bonding with the Pd species. Radical addition onto Pd followed by CO migratory insertion was unfavorable owing to the high energy barrier of the migratory insertion step. The regioselectivity of the C(sp3)−H carbonylation was also investigated by DFT. The results show that the regioselectivity is controlled by both the bond dissociation energy of the reacting C−H bond and the stability of the corresponding generated carbon radical. Competitive side reactions also affected the yield and regioselectivity owing to the rapid consumption of the stable radical intermediate. Carbonylation mechanism: DFT method M06‐L was used to investigate the mechanism of Pd‐catalyzed radical oxidative carbonylation of alkanes with alcohols to afford alkyl acid esters. The results show alkyl radicals prefer to add to the CO molecule to form a carbonyl radical before bonding with the Pd species. Regioselectivity is controlled by both the bond dissociation energy of reacting the C−H bond and the stability of the corresponding generated carbon radical. [ABSTRACT FROM AUTHOR]

[Display omitted] • Kinetic model of fluoroquinolones oxidation by Fe(VI) was built at pH 3.0–9.0. • Reactive sites and main reactions were proposed based on theoretical calculation. • FeVI, FeV, and FeIV were primary reactive species at both alkaline and acidic pH. • HO was yielded via Fenton or Fenton-like process at acidic pH in Fe(VI) oxidation. This study investigated the impact of pH on the efficiency of ferrate (Fe(VI), K 2 FeO 4) toward fluoroquinolone antibiotics, built kinetic models of Fe(VI) oxidation, and elucidated the involved active species during Fe(VI) oxidation at acidic and alkaline conditions. It was found that the second-order reaction rate constants (k app , M−1 s−1) of Fe(VI) with three fluoroquinolone antibiotics (i.e., enroxacin, ofloxacin, and norfloxacin) were strongly dependent on pH, and k app reached its maximum at pH about 6.5. The reactions between HFeO 4 -/H 2 FeO 4 and neutral/protonated fluoroquinolone antibiotics (X and XH+) were the major ones. Moreover, the reactive species were identified as high-valent iron species, i.e., Fe(VI), Fe(V), and Fe(IV), in alkaline solution, while hydroxyl radicals was generated through Fenton or Fenton-like processes at acidic condition with limited contribution. [ABSTRACT FROM AUTHOR]