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We report a mechanistic investigation of an aromatic dithioimide (2SS) displaying puzzling yet efficient photochemistry in ether solvents. Perplexingly, 2SS dissolved in ether solvents in a sealed and degassed vial was photochemically converted to the corresponding diimide (2OO), as determined by 1H NMR following product extraction. With no external sources of oxygen in the sample, could the oxygen in 2OO be from the ether itself? To study this unprecedented proposition, we attempt to uncover the ether's involvement in this reaction. As seen by laser‐flash photolysis, 2SS appears to first react with the solvent from its singlet excited state. Following the reaction by NMR under rigorously oxygen‐ and water‐free conditions led to the identification of a photoreductive pathway that quantitatively transformed one thione into a methylene to yield 2SH2. Subsequent oxidation of 2SH2 or irradiation of 2SS under air proved that molecular oxygen was indeed necessary to observe an oxidative pathway leading to 2OO, ruling out the initially proposed involvement of an ether oxygen. An explanation of 2SS desulfurization was further revealed through the study of solvent by‐products by GC‐MS analysis. Supported by DFT calculations, a mechanism is proposed to involve a chain reaction initiated by photochemically generated ether radical. [ABSTRACT FROM AUTHOR]

The photophysical and electrochemical properties for a series of BODIPY dyes with incremental 3‐ and 3,5‐vinyl conjugation, as well as incremental electron‐donating groups (anisole < triphenylamine < ferrocenyl), are presented. Insight into the influence of each vinyl‐conjugated electron‐donating group on both vis‐NIR absorption and fluorescence emission properties is provided. These trends are further corroborated by density functional theory computational analysis. Two of this series containing the 3,5‐bis(vinyltriphenylamine) and 3,5‐bis(vinylferrocenyl) substituents exhibit significant absorption cross sections in the biological transparency window justifying further investigation of their photoacoustic emission properties via both optical photoacoustic z‐scan and photoacoustic tomography experiments. Both the 3,5‐bis(vinyltriphenylamine) and 3,5‐bis(vinylferrocenyl) substituted BODIPY dyes exhibit quantitative photoacoustic quantum yields. Relative to the commercially available methylene blue and indocyanine green molecular photoacoustic contrast agents, the 3,5‐bis(vinyltriphenylamine)‐derived BODIPY exhibits the greatest photoacoustic emission and contrast upon excited‐state absorption at 685 nm excitation at a low power laser fluence (<20 mJ cm‐2). [ABSTRACT FROM AUTHOR]

The photophysical and electrochemical properties for a series of BODIPY dyes with incremental 3‐ and 3,5‐vinyl conjugation, as well as incremental electron‐donating groups (anisole < triphenylamine < ferrocenyl), are presented. Insight into the influence of each vinyl‐conjugated electron‐donating group on both vis‐NIR absorption and fluorescence emission properties is provided. These trends are further corroborated by density functional theory computational analysis. Two of this series containing the 3,5‐bis(vinyltriphenylamine) and 3,5‐bis(vinylferrocenyl) substituents exhibit significant absorption cross sections in the biological transparency window justifying further investigation of their photoacoustic emission properties via both optical photoacoustic z‐scan and photoacoustic tomography experiments. Both the 3,5‐bis(vinyltriphenylamine) and 3,5‐bis(vinylferrocenyl) substituted BODIPY dyes exhibit quantitative photoacoustic quantum yields. Relative to the commercially available methylene blue and indocyanine green molecular photoacoustic contrast agents, the 3,5‐bis(vinyltriphenylamine)‐derived BODIPY exhibits the greatest photoacoustic emission and contrast upon excited‐state absorption at 685 nm excitation at a low power laser fluence (<20 mJ cm‐2). [ABSTRACT FROM AUTHOR]

The photocatalytic hydroboration of alkenes and alkynes is reported. The use of newly‐designed copper photocatalysts with B2Pin2 permits the formation a boryl radical, which is used for hydroboration of a large panel of alkenes and alkynes. The hydroborated products were isolated in high yields, with excellent diastereoselectivities and a high functional group tolerance under mild conditions. The hydroboration reactions were developed under continuous flow conditions to demonstrate their synthetic utility. The reaction mechanism was studied and suggested an oxidation reaction between an in situ formed borate and the Cu‐photocatalyst in its excited state for the boryl radical formation. [ABSTRACT FROM AUTHOR]

We report detailed mechanistic investigations of an iron‐based catalyst system, which allows the α‐C−H oxidation of a wide variety of amines. In contrast to other catalysts that effect α‐C−H oxidations of tertiary amines, the system under investigation exclusively employs peroxy esters as oxidants. More common oxidants (e. g. tBuOOH) previously reported to affect amine oxidations via free radical pathways do not provide amine α‐C−H oxidation products in combination with the described catalyst system. The investigations described herein employ initial rate kinetics, kinetic profiling, DFT calculations as well as Eyring, kinetic isotope effect, Hammett, ligand coordination, and EPR studies to shed light on the Fe catalyst system. The obtained data suggest that the catalytic mechanism proceeds through C−H abstraction at a coordinated substrate molecule. This rate‐determining step occurs either through an Fe(IV) oxo pathway or a 2‐electron pathway at an Fe(II) intermediate with bound oxidant. DFT calculations indicate that the Fe(IV) oxo mechanism will be the preferred route of these two possibilities. We further show via kinetic profiling and EPR studies that catalyst activation follows a radical pathway, which is initiated by hydrolysis of PhCO3tBu to tBuOOH. Overall, the obtained mechanistic data support a non‐classical, Fe catalyzed pathway that requires substrate binding, inducing selectivity for α‐C−H functionalization. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of a series of donor-π-acceptor-π-donor (D-A-D) curcuminoid molecules is presented herein that incorporates π-extended aryl and electron-donating amino terminal functionalization. Computational evaluation shows these molecules possess quadrupolar character with the lowest energy transitions displaying high molar extinction coefficients with broad tunability through manipulation of terminal donating groups. Consistent with their quadrupolar nature, these molecules show varying degrees of solvatochromic behavior in both their absorption and emission spectra, which has been analyzed by Lippert-Mataga and Kamlet-Taft analysis. Photophysical and photoacoustic (PA) properties of these molecules have been investigated by the optical photoacoustic z-scan (OPAZ) method. Selected curcuminoid molecules display nonlinear behavior at a high laser fluence through excited state absorption that translates to the production of an enhanced photoacoustic emission. A relative comparison of "molar PA emission" is also presented with the crystal violet linear optical absorbing/linear PA emitting system being utilized as a standard reference material for OPAZ experiments. Furthermore, PA tomography experiments are presented to illustrate the enhanced PA contrast obtainable via an excited state absorption. [ABSTRACT FROM AUTHOR]

A visible-light-driven Minisci protocol that employs an inexpensive earth-abundant metal catalyst, decacarbonyldimanganese Mn2(CO)10, to generate alkyl radicals from alkyl iodides has been developed. This Minisci protocol is compatible with a wide array of sensitive functional groups, including oxetanes, sugar moieties, azetidines, tert-butyl carbamates (Boc-group), cyclobutanes, and spirocycles. The robustness of this protocol is demonstrated on the late-stage functionalization of complex nitrogen-containing drugs. Photophysical and DFT studies indicate a light-initiated chain reaction mechanism propagated by .Mn(CO)5. The rate-limiting step is the iodine abstraction from an alkyl iodide by .Mn(CO)5. [ABSTRACT FROM AUTHOR]

A visible-light-promoted iridium photoredox and nickel dual-catalyzed cross-coupling procedure for the formation C−N bonds has been developed. With this method, various aryl amines were chemoselectively cross-coupled with electronically and sterically diverse aryl iodides and bromides to forge the corresponding C−N bonds, which are of high interest to the pharmaceutical industries. Aryl iodides were found to be a more efficient electrophilic coupling partner. The coupling reactions were carried out at room temperature without the rigorous exclusion of molecular oxygen, thus making this newly developed Ir-photoredox/Ni dual-catalyzed procedure very mild and operationally simple. [ABSTRACT FROM AUTHOR]

Cover Feature: Mechanistic Insights into Fe Catalyzed -C-H Oxidations of Tertiary Amines (ChemCatChem 1/2021) Keywords: Iron catalysis; C-H oxidation; kinetics; DFT calculation; mechanistic analysis EN Iron catalysis C-H oxidation kinetics DFT calculation mechanistic analysis 4 4 1 01/18/21 20210112 NES 210112 B The Cover Feature b shows cast iron catalysis: Trialkyl amines cooked with the right recipe will take the oxygen from water to form the corresponding trialkyl amide. Iron catalysis, C-H oxidation, kinetics, DFT calculation, mechanistic analysis. [Extracted from the article]

The cover page of the journal "Angewandte Chemie" is presented.

Die Rädchen von Ir ‐ Photoredox ‐ und Ni ‐ Katalyse …… greifen ineinander und erzeugen eine leistungsstarke Kreuzkupplungsmaschinerie. M. S. Oderinde, J W. Johannes et al. beschreiben in ihrer Zuschrift auf S. 13413 ff. Arylaminierungen mit einem solchen dualen Katalysatorsystem unter Bestrahlung mit einer blauen LED. Die Doppelfunktion des Ir ‐ Komplexes in der Oxidation der Arylamine und der Reduktion von NiII über Außensphären ‐ Einelektronentransfer ermöglicht C ‐ N ‐ Kreuzkupplungen unter erstaunlich milden Bedingungen. [ABSTRACT FROM AUTHOR]

Highly chemoselective photoinduced Ni-catalyzed cross-coupling reactions of aryl, benzyl, and alkyl thiols with aryl and heteroaryl iodides in the presence of an Ir(III)-photoredox catalyst are developed. [ABSTRACT FROM AUTHOR]