Tethering Three Radical Cascades for Controlled Termination of Radical Alkyne -Annulations: Making Phenalenyl Ketones without Oxidants.

Although BuSn-mediated radical alkyne -annulations allow access to phenalenyl ring systems, the oxidative termination of these cascades provides only a limited selection of the possible isomeric phenalenone products with product selectivity controlled by the intrinsic properties of the new cyclic systems. In this work, we report an oxidant-free termination strategy that can overcome this limitation and enable selective access to the full set of isomerically functionalized phenalenones. The key to preferential termination is the preinstallation of a "weak link" that undergoes C-O fragmentation in the final cascade step.

Diverse Biological Activity of Benzofuroxan/Sterically Hindered Phenols Hybrids.

Combining two pharmacophores in a molecule can lead to useful synergistic effects. Herein, we show hybrid systems that combine sterically hindered phenols with dinitrobenzofuroxan fragments exhibit a broad range of biological activities. The modular assembly of such phenol/benzofuroxan hybrids allows variations in the phenol/benzofuroxan ratio.

α-Methylstilbene Isomers: Relationship of Structure to Photophysics and Photochemistry.

Significant differences in the photochemical and photophysical behavior of -α-methylstilbene and -stilbene have been attributed to structural changes caused by the steric requirements of the methyl group. We present here the X-ray structures of - and -α-methylstilbene (- and -MeSt). This is the first X-ray structure of a -stilbene.

Carboxylate as a Non-innocent L-Ligand: Computational and Experimental Search for Metal-Bound Carboxylate Radicals.

We show that the carboxylate radical acts as an L-ligand with certain high-spin transition metal centers. Such coordination preserves the O-radical character needed for C-H activation via hydrogen atom transfer. Capture of the new C-radical by the metal and subsequent reductive elimination leads to formal C-H acyloxylation.

Remote Stereoelectronic Effects in Pyrrolidone- and Caprolactam-Substituted Phenols: Discrepancies in Antioxidant Properties Evaluated by Electrochemical Oxidation and H-Atom Transfer Reactivity.

New antioxidants are commonly evaluated via two main approaches, i.e., the ability to donate an electron and the ability to intercept free radicals.

Anomeric effect, hyperconjugation and electrostatics: lessons from complexity in a classic stereoelectronic phenomenon.

Understanding the interplay of multiple components (steric, electrostatic, stereoelectronic, dispersive, ) that define the overall energy, structure, and reactivity of organic molecules can be a daunting task. The task becomes even more difficult when multiple approaches based on different physical premises disagree in their analysis of a multicomponent molecular system. Herein, we will use a classic conformational "oddity", the anomeric effect, to discuss the value of identifying the key contributors to reactivity that can guide chemical predictions.

Correction: Stereoelectronic power of oxygen in control of chemical reactivity: the anomeric effect is not alone.

Correction for 'Stereoelectronic power of oxygen in control of chemical reactivity: the anomeric effect is not alone' by Igor V. Alabugin , , 2021, DOI: 10.1039/d1cs00386k.

Stereoelectronic power of oxygen in control of chemical reactivity: the anomeric effect is not alone.

Although carbon is the central element of organic chemistry, oxygen is the central element of stereoelectronic control in organic chemistry. Generally, a molecule with a C-O bond has both a strong donor (a lone pair) and a strong acceptor (, a σ* orbital), a combination that provides opportunities to influence chemical transformations at both ends of the electron demand spectrum. Oxygen is a stereoelectronic chameleon that adapts to the varying situations in radical, cationic, anionic, and metal-mediated transformations.

Synthesis of unstrained Criegee intermediates: inverse α-effect and other protective stereoelectronic forces can stop Baeyer-Villiger rearrangement of γ-hydroperoxy-γ-peroxylactones.

We address this question by exploring the interplay between the primary and secondary stereoelectronic effects in the Baeyer-Villiger (BV) rearrangement by experimental and computational studies of γ-OR-substituted γ-peroxylactones, the previously elusive non-strained Criegee intermediates (CI). These new cyclic peroxides were synthesized by the peroxidation of γ-ketoesters followed by cyclization using a BF·EtO/HO system. Although the primary effect (alignment of the migrating C-R bond with the breaking O-O bond) is active in the 6-membered ring, weakening of the secondary effect (donation from the OR lone pair to the breaking C-R bond) provides sufficient kinetic stabilization to allow the formation and isolation of stable γ-hydroperoxy-γ-peroxylactones with a methyl-substituent in the C6-position.

Determination of the p Values of -Resveratrol, a Triphenolic Stilbene, by Singular Value Decomposition. Comparison with Theory.

Several independent determinations of the p values of -resveratrol in water have led to conflicting results. Singular value decomposition analysis of UV absorption spectra of -resveratrol (Resv) in N-outgased aqueous solutions buffered to pH values in the 7.0-13.

Anilinium Salts in Polymer Networks for Materials with Mechanical Stability and Mild Thermally Induced Dynamic Properties.

Dynamic nucleophilic exchange of quaternary anilinium salts has been incorporated into rehealable and malleable polymeric materials that can be activated under mild (60 °C) thermal stimulus. The mechanism of dynamic exchange between quaternary anilinium salt and free aniline was assessed in small-molecule model experiments. The dynamic exchange was found to be dissociative in nature, due to the indirect S2 mechanism, where initially the bromide anion attacks the anilinium salt to generate an alkyl bromide which undergoes subsequent attack by a free aniline group.