Accessing 1,8-Naphthyridone-3-carboxylic Acid Derivatives and Application to the Synthesis of Amfonelic Acid.

1,8-Naphthyridone-3-carboxyl is the core structure of several on-market antibacterial drugs. It has prompted significant interest from the synthetic community. Here, we report a practical synthesis of diversely functionalized 1,8-naphthyridone-3-carboxylic acid derivatives starting from readily available and inexpensive nicotinic acid derivatives. All key steps have been optimized. Furthermore, the usefulness of this protocol has been exemplified by the first synthesis of amfonelic acid.

Transition metal-free C(sp3)-H selenation of ß-ketosulfones.

The installation of selenium groups has become an essential step across a number of industries such as agrochemicals, drug discovery, and materials. However, direct C(sp3)-H selenation, which is most atom economical, remains a formidable challenge, and only a few examples have been reported to date. In this article, we introduce the transition metal-free C(sp3)-H selenation with the easily available ß-ketosulfones and diselenides as the material source. This benign protocol permits access to a broad spectrum of α-aryl(alkyl) seleno-ß-ketosulfones in high yields with outstanding functional group compatibility. Distinct advantages of this protocol over all previous methods encompass the utilization of base and air as an oxidant, room temperature, and enhanced green chemistry matrices.

Synthesis of α/ß-Aromatic Peroxy Thiols Mediated by Iodine Source.

Peroxygenated compounds have wide applications in various fields, including chemistry, pharmaceutical chemistry, medicine, and materials science. However, there is still a need for more efficient and environmentally friendly synthesis methods for such compounds. Herein, we investigated the two-step, one-pot, regioselective synthesis of α/ß-aromatic peroxy thiols. We explored various substrates and solvents for the reaction and identified the optimal reaction conditions. We successfully obtained several peroxy thiols in moderate to good yields via the selective generation of effective intermediates of iodoalkyl peroxides at room temperature without the need for metal catalysts.

Photoredox aerobic oxidative cycliation of N-arylacrylamides with benzylalcohols.

While the radical coupling/cyclization of N-arylacrylamides has been well established for the synthesis of functionalized oxindoles, in the present work, a visible-light-induced aerobic oxidative coupling/cyclization reaction of N-arylacrylamides with benzylalcohols has been developed. The combination of LiBr and benzophenone as the additive was found to be highly effective to enhance the catalytic efficacy. This protocol offers a mild alternative access to structurally valuable hydroxyalkyl oxindoles. Mechanistic studies reveal that the bromo radical in situ formed through the photoredox SET process under aerobic conditions enables efficient HAT to generate the key hydroxyalkyl radical intermediate.

Visible-Light-Promoted [3 + 2] Cyclization of Chalcones with 2-Mercaptobenzimidazoles: A Protocol for the Synthesis of Imidazo[2,1-b]thiazoles.

A visible-light-promoted [3 + 2] cyclization between chalcones and 2-mercaptobenzoimidazoles for the construction of diverse imidazo[2,1-b]thiazoles via an electron-donor-acceptor (EDA) complex has been developed. This novel aminothiolation can be realized under only visible light irradiation without the aid of external photocatalysts, transition metals, and oxidants. Mechanistic investigations have revealed that the thiol anions and chalcones form EDA complexes, providing a novel strategy for the synthesis of imidazo[2,1-b]thiazoles.

A visible-light-induced thiol addition/aerobic oxidation cascade reaction of epoxides and thiols for the synthesis of ß-hydroxylsulfoxides.

A photochemical thiol addition/aerobic oxidation cascade reaction has been developed. This protocol enables efficient oxidative coupling of epoxides and thiols to access structurally valuable ß-hydroxylsulfoxides. A broad range of functional groups are compatible to obtain moderate to good yields of the target products. Mechanistic studies revealed a sequential reaction pathway involving base-promoted thiol addition of thiols to epoxides and visible-light-induced aerobic oxygenation of thioethers.

Electrochemical Enabled Cascade Phosphorylation of N-H/O-H/S-H Bonds with P-H Compounds: An Efficient Access to P(O)-X Bonds.

An electrochemical three component cascade phosphorylation reaction of various heteroatoms-containing nucleophiles including carbazoles, indoles, phenols, alcohols, and thiols with Ph2 PH has been established. Electricity is used as the "traceless" oxidant and water and air are utilized as the "green" oxygen source. All kinds of structurally diverse organophosphorus compounds with P(O)-N/P(O)-O/P(O)-S bonds are assembled in moderate to excellent yields (three categories of phosphorylation products, 50 examples, up to 97 % yield). A tentative free radical course is put forward to rationalize the reaction procedure.

Gold-catalyzed C(sp3)-H bond functionalization.

C-H bonds are ubiquitous in organic molecules. Homogenous gold-catalyzed direct functionalization of unsaturated C-H bonds has emerged as a powerful method in our synthetic toolbox. However, Csp(3)-H bonds have larger dissociation energy and lower proton acidity, and thus the efficient and exquisitely selective cleavage of this kind of chemical bonds for the formation of new carbon-carbon and carbon-heteroatom bonds is still a great challenge. In this tutorial review, we will highlight the recent achievements of gold-catalyzed oxidative and redox-neutral Csp(3)-H bond functionalization, which opens new avenues for economical and sustainable construction of fine chemicals.

Ruthenium-catalyzed C7 amidation of indoline C-H bonds with sulfonyl azides.

A ruthenium-catalyzed direct C7 amidation of indoline C-H bonds with sulfonyl azides was developed. This procedure allows the synthesis of a variety of 7-amino-substituted indolines, which are useful in pharmaceutical. The good functional tolerances, as well as the mild conditions, are prominent feature of this method.

Visible-light-promoted radical C-H trifluoromethylation of free anilines.

The trifluoromethyl-substituted anilines are biologically active compounds and useful building blocks. In this communication, we have developed the first visible-light-induced radical trifluoromethylation of free anilines with the commercially available and easily handled Togni reagent at room temperature. The resulting products were successfully transformed into a variety of valuable fluorine-containing molecules and heterocyclic compounds. This protocol provides an economical and powerful route to trifluoromethylated free anilines.

Room temperature decarboxylative trifluoromethylation of α,ß-unsaturated carboxylic acids by photoredox catalysis.

A visible-light-induced decarboxylative trifluoromethylation of α,ß-unsaturated carboxylic acids, which uses the Togni reagent as the CF3 source is disclosed. The corresponding trifluoromethylated alkenes were obtained in moderate to high yields with excellent functional group tolerance at ambient temperature. Preliminary mechanistic analyses suggest a radical-type mechanism.

Catalyst-controlled switchable phosphination of α-diazoesters.

Organocatalyst and metal provide different products: a catalyst-controlled switchable phosphination of α-diazoesters has been developed by using DBU and copper as catalysts. It provided an efficient synthetic method for the construction of various phosphorus compounds via the formation of N-P and C-P bonds.

Efficient synthesis of ß-enaminones and ß-enaminoesters catalyzed by gold (I)/silver (I) under solvent-free conditions.

An efficient method for the synthesis of ß-enaminones and ß-enaminoesters using a combination of [(PPh(3))AuCl]/AgOTf as catalyst has been developed. The reaction between 1,3-dicarbonyl compounds and primary amines was carried out under solvent-free conditions with low catalyst loading in good to excellent yields at room temperature.