N-Hydroxyphthalimide-Mediated Electrochemical Denitrogenation of Aroylhydrazides to Generate Acyl Radicals and Their Applications in the Syntheses of Fluorenones

La(OTf)3-Catalyzed Benzannulation of 2-Arylidene-1H-indene-1,3(2H)-diones with Enamino Esters: Direct Access to Functionalized Fluorenone Derivatives

An attractive method for the preparation of functional fluorenone derivatives has been developed via La(OTf)3-catalyzed benzannulation of 2-arylidene-1H-indene-1,3(2H)-diones with enamino esters. The reaction involves Michael addition, intramolecular cyclization, dehydration, and aromatization in a one-step process and affords a wide range of functional fluorenone derivatives in moderate to good yields. Moreover, this protocol provides several advantages, including broad substrate scope, readily available materials, high atom economy, and applicability for large-scale synthesis.

Electrochemical quinuclidine-mediated Minisci-type acylation of N-heterocycles with aldehydes

The electro-generation of acyl radicals from both aromatic and aliphatic aldehydes remains an unmet challenge. We provide a solution to this challenge by merging electro-oxidation and a quinuclidine-mediated hydrogen atom transfer strategy. The generation of acyl radicals at decreased applied potentials compared to that of formyl oxidation exhibits excellent functional group compatibility.

Organocatalyzed Photoelectrochemistry for the Generation of Acyl and Phosphoryl Radicals through Hydrogen Atom-Transfer Process

An organocatalyzed photoelectrochemical method for the generation of acyl and phosphoryl radicals from formamides, aldehydes, and phosphine oxides has been developed. This protocol utilizes 9,10-phenanthrenequinone (PQ) as both a molecular catalyst and a hydrogen atom-transfer (HAT) reagent, eliminating the requirement for external metal-based reagents, HAT reagents, and oxidants. The generated acyl radicals can be applied to a range of radical-mediated transformation reactions, including C-H carbamoylation of heteroarenes, intermolecular tandem radical cyclization of CF3-substituted N-arylacrylamides, as well as intramolecular cyclization reactions. The use of acyl radicals in these transformations offers an efficient and sustainable approach to accessing structurally diverse carbonyl compounds.

Electrochemical C-H/C-C Bond Oxygenation: A Potential Technology for Plastic Depolymerization

Herein, we provide eco-friendly and safely operated electrocatalytic methods for the selective oxidation directly or with water, air, light, metal catalyst or other mediators serving as the only oxygen supply. Heavy metals, stoichiometric chemical oxidants, or harsh conditions were drawbacks of earlier oxidative cleavage techniques. It has recently come to light that a crucial stage in the deconstruction of plastic waste and the utilization of biomass is the selective activation of inert C(sp3 )-C/H(sp3 ) bonds, which continues to be a significant obstacle in the chemical upcycling of resistant polyolefin waste. An appealing alternative to chemical oxidations using oxygen and catalysts is direct or indirect electrochemical conversion. An essential transition in the chemical and pharmaceutical industries is the electrochemical oxidation of C-H/C-C bonds. In this review, we discuss cutting-edge approaches to chemically recycle commercial plastics and feasible C-C/C-H bonds oxygenation routes for industrial scale-up.

Electricity-Promoted Friedel-Crafts Acylation of Biarylcarboxylic Acids

An electricity-promoted method for Friedel-Crafts acylation of biarylcarboxylic acids is described in this research. Various fluorenones can be accessed in up to 99% yields. During the acylation, electricity plays an essential role, which might motivate the chemical equilibrium by consuming the generated TFA. This study is predicted to provide an avenue to realize Friedel-Crafts acylation in a more environmentally friendly process.

NHPI-Mediated Electrochemical α-Oxygenation of Amides to Benzimides

This report describes a mild electrochemical α-oxygenation of a wide range of linear and cyclic benzamides mediated by N-hydroxyphthalimide (NHPI) in an undivided cell using O₂ as the oxygen source and 2,4,6-trimethylpyridine perchlorate as an electrolyte. The radical scavenger experiment and the ¹⁸O labeling experiment were carried out, which indicated the involvement of a radical pathway and suggested O₂ as an oxygen source in the imides, respectively.

Metal-Free Synthesis of N-Heterocycles via Intramolecular Electrochemical C-H Aminations

N-heterocycles are key structural units in many drugs, biologically interesting molecules and functional materials. To avoid the residues of metal catalysts, the construction of N-heterocycles under metal-free conditions has attracted much research attention in academia and industry. Among them, the intramolecular electrochemical C-H aminations arguably constitute environmentally friendly methodologies for the metal-free construction of N-heterocycles, mainly due to the direct use of clean electricity as the redox agents. With the recent renaissance of organic electrosynthesis, the intramolecular electrochemical C-H aminations have undergone much progress in recent years. In this article, we would like to summarize the advances in this research field since 2019. The emphasis is placed on the reaction design and mechanistic insight. The challenges and future developments in the intramolecular electrochemical C-H aminations are also discussed.

Radical coupling reactions of hydrazines via photochemical and electrochemical strategies

Hydrazines are versatile building blocks in organic synthesis.