Electrochemical utilization of methanol and methanol-d4 as a C1 source to access (deuterated) 2,3-dihydroquinazolin-4(1H)-one

Electrochemical alkylation of C(sp2)-H bonds via halogen-atom transfer (XAT) from alkyl iodides

Here, we present an electrochemical C(sp2)-H bond alkylation of unactivated alkyl iodides via a halogen-atom transfer (XAT) process under mild conditions. This strategy avoids the drawbacks associated with sacrificing reactive metal anodes in electrochemical direct reduction and demonstrates excellent functional group tolerance.

Methanol Activation: Strategies for Utilization of Methanol as C1 Building Block in Sustainable Organic Synthesis

The development of efficient and sustainable chemical processes which use greener reagents and solvents, currently play an important role in current research. Methanol, a cheap and readily available resource from chemical industry, could be activated by transition metal catalysts. This review focuses in covering the recent five-years literature and provides a systematic summary of strategies for methanol activation and the use in organic chemistry. Based on these strategies, many new synthetic methods have been developed for methanol utilization as the C1 building block in methylation, hydromethylation, aminomethylation, formylation reactions, as well as the syntheses of urea derivatives and heterocycles. The achievements, synthetic applications, limitations, some advanced approaches, and future perspectives of the methanol activation methodologies have been described in this review.

Manganaelectro-Catalyzed Cyclization of o-Aminoarylketones with Ammonia: An Approach to 1,2-Dihydroquinazolines

A manganaelectro-catalyzed cyclization reaction of 2-aminoarylketones with simple alcohols and ammonia under mild conditions is reported for the first time. The cooperative catalysis effectively enhances the oxidation of primary alcohols into aldehydes, thus enabling the synthesis of substituted 1,2-dihydroquinazolines in good to excellent yields. In addition, the utilities of this method are highlighted in the construction of biologically active molecules that would otherwise be difficult to access through a traditional method.

Selective Oxidative Cleavage of Benzyl C-N Bond under Metal-Free Electrochemical Conditions

With the growing significance of green chemistry in organic synthesis, electrochemical oxidation has seen rapid development. Compounds undergo oxidation-reduction reactions through electron transfer at the electrode surface. This article proposes the use of electrochemical methods to achieve cleavage of the benzyl C-N bond. This method selectively oxidatively cleaves the C-N bond without the need for metal catalysts or external oxidants. Additionally, primary, secondary, and tertiary amines exhibit good adaptability under these conditions, utilizing water as the sole source of oxygen.

Electrochemical Synthesis of Spirolactones from α-Tetralone Derivatives with Methanol as a C1 Source

Spirolactones are widely found in pharmaceuticals and bioactive natural products. However, efficient and environmentally friendly approaches to accessing spirolactones are still highly desirable. Herein, a novel electrochemical synthesis of spirolactones from α-tetralone derivatives with methanol as a C1 source is described. This electrochemical reaction exhibits a high efficiency and good functional group tolerance.

Sustainable Electrochemical Benzylic C-H Oxidation Using MeOH as an Oxygen Source

New methods and strategies for the direct oxidation of benzylic C-H bonds are highly desirable, owing to the importance of ketone motifs in significant organic transformations and the synthesis of valuable molecules, including pharmaceuticals, pesticides, and fine chemicals. Herein, we describe an electrochemical benzylic C-H oxidation strategy for the synthesis of ketones using MeOH as an oxygen source. Inexpensive and safe KBr serves as both an electrolyte and a bromide radical precursor in the reaction. This transformation also offers several advantages such as mild conditions, broad functional group tolerance, and operational simplicity. Mechanistic investigations by control experiments, radical scavenging experiments, electron paramagnetic resonance (EPR), kinetic studies, cyclic voltammetry (CV), and in-situ Fourier transform infrared (FTIR) spectroscopy support a pathway involving the formation and transformation of benzyl methyl ether via hydrogen atom transfer (HAT) and single-electron transfer (SET). The practical application of our strategy is highlighted by the successful synthesis of five pharmaceuticals, namely lenperone, melperone, diphenhydramine, cinnarizine, and flunarizine.

Electrochemically Promoted Three-Component Reaction to N-Sulfonyl Amidines

In this study, a multicomponent reaction via the Mannich intermediate was developed using methanol, secondary amine, and sulfonamide as starting materials. This method uses methanol as a green C1 source. The substrate scope is wide, and the yield is good. The mechanistic study shows that methanol generates formaldehyde under electrochemical conditions, and sulfonyl amidine as a nucleophile reacts with Schiff base intermediates to form N-sulfonyl amidine in a single step.

Surface modification of a screen-printed electrode with a flower-like nanostructure to fabricate a guanine DNA-based electrochemical biosensor to determine the anticancer drug pemigatinib

The present study developed a DNA biosensor to determine pemigatinib for the first time. Three-dimensional carnation flower-like Eu3+:β-MnO2 nanostructures (3D CF-L Eu3+:β-MnO2 NSs) and a screen-printed electrode (SPE) modified with polyaniline (PA) were employed. The double-stranded DNA was also immobilized completely on the PA/3D CF-L Eu3+:β-MnO2 NSs/SPE. Then, electrochemical techniques were used for characterizing the modified electrode. After that, the interaction between pemigatinib and DNA was shown by a reduction in the oxidation current of guanine using differential pulse voltammetry (DPV). According to the analysis, the dynamic range of pemigatinib was between 0.001 and 180.0 μM, indicating the new electrode has a low limit of detection (LOD = 0.23 nM) for pemigatinib. Afterwards, pemigatinib in real samples was measured using the PA/3D CF-L Eu3+:β-MnO2 NSs/SPE loaded with ds-DNA. The proposed DNA biosensor showed good selectivity toward pemigatinib in the presence of other interference analytes, such as other ions, structurally related pharmaceuticals, and plasma proteins. In addition, the interaction site of pemigatinib with DNA was predicted by molecular docking, which showed the interaction of pemigatinib with the guanine bases of DNA through a groove binding mode. Finally, we employed the t-test to verify the capability of the ds-DNA/PA/3D CF-L Eu3+:β-MnO2 NSs/SPE for analyzing pemigatinib in real samples.

Photo-Induced C1 Substitution Using Methanol as a C1 Source

The development of sustainable and efficient C1 substitution methods is of central interest for organic synthesis and pharmaceuticals production, the methylation motifs bound to a carbon, nitrogen, or oxygen atom widely exist in natural products and top-selling drugs. In the past decades, a number of methods involving green and inexpensive methanol have already been disclosed to replace industrial hazardous and waste-generating C1 source. Among the various efforts, photochemical strategy is considered as a "renewable" alternative that shows great potential to selectively activate methanol to achieve a series of C1 substitutions at mild conditions, typically C/N-methylation, methoxylation, hydroxymethylation, and formylation. Herein the recent advances in selective transformation of methanol to various C1 functional groups via well-designed photochemical systems involving different types of catalysts or not is systematically reviewed. Both the mechanism and corresponding photocatalytic system were discussed and classified on specific methanol activation models. Finally, the major challenges and perspectives are proposed.

Metal-Free Electrochemically Reductive Deuteration of C═N Bonds with D2O toward Deuterated Amines

Environmentally friendly and highly efficient synthesis of α-deuterated amines is achieved via a concise electrochemical process using D₂O as deuterium source without any external reductants or catalysts. Various imines are compatible, affording the desired products in high yields and D-incorporation. Gram-scale synthesis and flow-cell electrochemistry technology are used to synthesize deuterated pharmaceutical amines and their intermediates. Mechanistic studies reveal a plausible process, including the formation of carbanion species followed by deuterium atom transfer.

Synthesis of acridines via copper-catalyzed amination/annulation cascades between arylboronic acids and anthranils

Copper-catalyzed tandem cyclization reactions between arylboronic acids and anthranils have been established, providing new approaches for one-pot assembly of azacycle acridines. This one-pot protocol features simple operation, precious-metal-free conditions and good functional group compatibility, thus providing an efficient approach for the synthesis of a variety of acridines in moderate to good yields.

Electrochemical selective annulative amino-ketalization and amino-oxygenation of 1,6-enynes

A new electrochemical selective annulative amino-ketalization and amino-oxygenation of 1,6-enynes with disulfonimides and alcohols is reported, producing a series of functionalized benzofurans under catalyst- and oxidant-free conditions. The annulative aminoketalization proceeds with simple short-chain alcohols such as methanol, ethanol and n-propanol as O-nucleophilic reagents, while the reaction occurs in the annulative aminooxygenation direction in the presence of water and large steric sec-butyl alcohol (SBA).

Copper-Catalyzed Reactions of Alkenyl Boronic Esters via Chan-Evans-Lam Coupling/Annulation Cascades: Substrate Selective Synthesis of Dihydroquinazolin-4-ones and Polysubstituted Quinolines

Copper-catalyzed cascade cyclization reactions between alkenyl boronic esters and N-H-based nucleophiles have been established, providing new approaches for one-pot assembly of azacycles. Following the Chan-Evans-Lam C-N couplings, the cyclization processes occur via divergent pathways based on the utilized substrates, affording hydroamination product dihydroquinazolin-4-ones or aromatization product quinolines. Via this one-pot C-N coupling/annulation cascade, the target substituted azacycles can be obtained in moderate to good yields in each case.