Solvent Anions Enable Photoinduced Borylation and Phosphonation of Aryl Halides via EDA Complexes.

We report the synthesis of aryl boronic esters and aryl phosphonate esters promoted by visible-light in the absence of transition-metals or photoredox catalysts. The transformation proceeds at room temperature using sodium hydride, as a non-nucleophilic base, and exhibits functional group tolerance for anilines, amides, and esters. UV-vis spectroscopy, radical trapping experiments, and computational (TD-DFT) calculations suggest an electron-donor-acceptor (EDA) complex between solvent anions and aryl halides as the species responsible for this reactivity.

Photoinduced C(sp)-H Chalcogenation of Amide Derivatives and Ethers via Ligand-to-Metal Charge-Transfer.

A photoinduced, iron(III) chloride-catalyzed C-H activation of -methyl amides and ethers leads to the formation of C-S and C-Se bonds via a ligand-to-metal charge transfer (LMCT) process. This methodology converts secondary and tertiary amides, sulfonamides, and carbamates into the corresponding amido--acetal derivatives in good yields. Mechanistic work revealed that this transformation proceeds through a hydrogen atom transfer (HAT) involving chlorine radical intermediates.

Dimsyl Anion Enables Visible-Light-Promoted Charge Transfer in Cross-Coupling Reactions of Aryl Halides.

A methodology is reported for visible-light-promoted synthesis of unsymmetrical chalcogenides enabled by dimsyl anion in the absence of transition-metals or photoredox catalysts. The cross-coupling reaction between aryl halides and diaryl dichalcogenides proceeds with electron-rich, electron-poor, and heteroaromatic moieties. Mechanistic investigations using UV-Vis spectroscopy, time-dependent density functional theory (TD-DFT) calculations, and control reactions suggest that dimsyl anion forms an electron-donor-acceptor (EDA) complex capable of absorbing blue light, leading to a charge transfer responsible for generation of aryl radicals from aryl halides.

Transition-Metal-Free Photoredox Phosphonation of Aryl C-N and C-X Bonds in Aqueous Solvent Mixtures.

Herein, we present an efficient and mild methodology for the synthesis of aromatic phosphonate esters in good to excellent yields using 10-phenothiazine, an inexpensive commodity chemical, as a photoredox catalyst. The reaction exhibits wide functional group compatibility enabling the transformation in the presence of ketone, amide, ester, amine, and alcohol moieties. Importantly, the reaction proceeds using a green solvent mixture primarily composed of water, thus lowering the environmental footprint of this transformation compared to current methods.

Photoredox Polyfluoroarylation of Alkyl Halides via Halogen Atom Transfer.

Polyfluoroarene moieties are of interest in medicinal chemistry, agrochemicals, and material sciences. Herein, we present the first polyfluoroarylation of unactivated alkyl halides via a halogen atom transfer process. This method converts primary, secondary, and tertiary alkyl halides into the respective polyfluoroaryl compounds in good yields in the presence of amide, carbamate, ester, aromatic, and sulfonamide moieties, including derivatives of complex bioactive molecules.

Metal-free visible-light-promoted C(sp)-H functionalization of aliphatic cyclic ethers using trace O.

Presented is a light-promoted C-C bond forming reaction yielding sulfone and phosphate derivatives at room temperature in the absence of metals or photoredox catalyst. This transformation proceeds in neat conditions through an auto-oxidation mechanism which is maintained through the leaching of trace amounts of O as sole green oxidant.

Synthesis of Imide and Amine Derivatives via Deoxyamination of Alcohols Using -Haloimides and Triphenylphosphine.

A deoxyamination methodology of activated and unactivated alcohols is presented. The reaction is mediated by phosphonium intermediates generated from -haloimides and triphenylphosphine. The protocol allows for the synthesis of phthalimide and amine derivatives in moderate to good yields at room temperature.

Photochemical Regioselective C(sp)-H Amination of Amides Using -Haloimides.

A metal-free regioselective C(sp)-H amination of amides using -haloimides in the presence of lithium -butoxide and visible light is presented herein. This photoexcited approach is straightforward, and it aminates a wide variety of amides under mild conditions without the use of photocatalysts, external radical initiators, or oxidants. A halogen-bonded intermediate between the -butoxide base and the -haloimide is proposed to be responsible for the increased photoreactivity.

Amide Synthesis through the In Situ Generation of Chloro- and Imido-Phosphonium Salts.

We describe a methodology for the amidation of carboxylic acids by generating phosphonium salts in situ from -chlorophthalimide and triphenylphosphine. Aliphatic, benzylic, and aromatic carboxylic acids can be transformed into their amide counter parts using primary and secondary amines. This functional group interconversion is achieved at room temperature in good to excellent yields.

Regioselective α-Amination of Ethers Using Stable N-Chloroimides and Lithium tert-Butoxide.

Herein we describe a metal-free regioselective α-amination of ethers mediated by N-chloroimides in ethereal solvents in the presence of lithium tert-butoxide. This reactivity of N-chloroimides leads to the synthesis of hemiaminal ethers in good to excellent yields at room temperature. This C-H functionalization is achieved without the use of a light, heat source, or external radical initiators.

Exhaustive Suzuki-Miyaura reactions of polyhalogenated heteroarenes with alkyl boronic pinacol esters.

A novel Suzuki-Miyaura protocol is described that enables the exhaustive alkylation of polychlorinated pyridines. This method facilitates a formal synthesis of normuscopyridine and the rapid assembly of a dumbbell shaped portion of a [2]rotaxane.

Gold(I)-Catalyzed Intramolecular Hydroamination of Unactivated Terminal and Internal Alkenes with 2-Pyridones.

The cationic gold phosphine complex [(P1)Au(NCMe)]SbF [P1 = P(t-Bu)o-biphenyl; 2] catalyzes the intramolecular hydroamination of 6-alkenyl-2-pyridones to form 1,6-carboannulated 2-pyridones in high yield. The hydroamination of 6-(γ-alkenyl)-2-pyridones was effective for monosubstituted and 1,1- and 1,2-disubstituted aliphatic alkenes, and the method was likewise effective for the hydroamination of 6-(δ-alkenyl)-2-pyridones. Spectroscopic analysis of mixtures of 6-(3-butenyl)-2-pyridone, (P1)AuCl, and AgSbF established the N-bound 2-hydroxypyridine complex [(P1)Au(NCH-2-OH-6-CHCHCH═CH)] SbF as the catalyst resting state.

Selective and Serial Suzuki-Miyaura Reactions of Polychlorinated Aromatics with Alkyl Pinacol Boronic Esters.

Among cross-coupling reactions, the Suzuki-Miyaura transformation stands out because of its practical advantages, including the commercial availability and low toxicity of the required reagents, mild reaction conditions, and functional group compatibility. Nevertheless, few conditions can be used to cross-couple alkyl boronic acids or esters with aryl halides, especially 2-pyridyl halides. Herein, we describe two novel Suzuki-Miyaura protocols that enable selective conversion of polychlorinated aromatics, with a focus on reactions to convert 2,6-dichloropyridines to 2-chloro-6-alkylpyridines or 2-aryl-6-alkylpyridines.

Chemoselective detection and discrimination of carbonyl-containing compounds in metabolite mixtures by 1H-detected 15N nuclear magnetic resonance.

NMR spectra of mixtures of metabolites extracted from cells or tissues are extremely complex, reflecting the large number of compounds that are present over a wide range of concentrations. Although multidimensional NMR can greatly improve resolution as well as improve reliability of compound assignments, lower abundance metabolites often remain hidden. We have developed a carbonyl-selective aminooxy probe that specifically reacts with free keto and aldehyde functions, but not carboxylates.

Electron Ionization-Induced Release of Coded Isotopic Reporter Ions in an Zone of Minimal Interference for Quantifiable, Multiplexed GC-MS Analyses.

We describe an isotope coding strategy that enables simultaneous GC-MS analysis of multiple samples for substrate identification and quantification. The method relies on direct measurement of isotopic ethyl carbenium ions serving as mass spectral tags in a zone of minimal interference (ZMI) at m/z 31-37. Sample aldehyde and ketone mixtures were reacted with isotopic 2-aminooxyethyl propionates to illustrate the method, which determined the relative abundance of the mixed compounds with an average 95% accuracy.

A chemoselective, one-pot transformation of aldehydes to nitriles.

This paper describes a procedure for direct conversion of aldehydes to nitriles using O-(diphenylphosphinyl)hydroxylamine (DPPH). Aldehydes are smoothly transformed to their corresponding nitriles by heating with DPPH in toluene. The reaction can be accomplished in the presence of alcohol, ketone, ester, or amine functionality.

Fragmentation of oxime and silyl oxime ether odd-electron positive ions by the McLafferty rearrangement: new insights on structural factors that promote α,β fragmentation.

The McLafferty rearrangement is an extensively studied fragmentation reaction for the odd-electron positive ions from a diverse range of functional groups and molecules. Here, we present experimental and theoretical results of 12 model compounds that were synthesized and investigated by GC-TOF MS and density functional theory calculations. These compounds consisted of three main groups: carbonyls, oximes and silyl oxime ethers.

Fluorophore-gold nanoparticle complex for sensitive optical biosensing and imaging.

Fluorophores have been extensively used as the signal mediator in biosensing and bioimaging for a long time. Enhancement of fluorescence can amplify the signal, thus improving the sensitivity, enabling earlier and accurate disease detection and diagnosis. Some metal nanoparticles, such as gold and silver, can generate a strong electromagnetic field on their surface (surface plasmon field) upon receiving photonic energy.