Nucleo-Palladation-Triggering Alkene Functionalization: A Route to γ-Lactones

Metal-free synthesis of 1,3-dichloro-1,5-diarylpentan-5-ones via cascade oxidative radical addition of styrenes with CHCl3

A novel and efficient metal-free cascade oxidative radical addition of styrenes is developed for the construction of 1,3-dichloro-1,5-diarylpentan-5-ones. This protocol presents a practical one-pot procedure that delivers highly functionalized 1,3-dichloro-1,5-diarylpentan-5-ones in moderate-to-good yields with a broad substrate scope under mild conditions.

Metal-Catalyst-Controlled Divergent Synthesis of γ-Butyrolactones via Intramolecular Coupling of Epoxides with Alcohols

A metal-controlled divergent protocol for the synthesis of α- and β-substituted γ-butyrolactones was developed through intramolecular coupling of epoxides with alcohols. This method provides an efficient and practicable way to afford γ-butyrolactones with good efficiency, excellent regioselectivity, and broad substrate scope.

Overcoming the limitations of Kolbe coupling with waveform-controlled electrosynthesis

The Kolbe reaction forms carbon-carbon bonds through electrochemical decarboxylative coupling. Despite more than a century of study, the reaction has seen limited applications owing to extremely poor chemoselectivity and reliance on precious metal electrodes. In this work, we present a simple solution to this long-standing challenge: Switching the potential waveform from classical direct current to rapid alternating polarity renders various functional groups compatible and enables the reaction on sustainable carbon-based electrodes (amorphous carbon). This breakthrough enabled access to valuable molecules that range from useful unnatural amino acids to promising polymer building blocks from readily available carboxylic acids, including biomass-derived acids. Preliminary mechanistic studies implicate the role of waveform in modulating the local pH around the electrodes and the crucial role of acetone as an unconventional reaction solvent for Kolbe reaction.

Development of a Modified System to Provide Improved Diastereocontrol in the Linear-Selective Cu-Catalyzed Reductive Coupling of Ketones and Allenamides

Chiral γ-lactones are prevalent organic architectures found in a large array of natural products. In this work, we disclose the development of a modified catalytic system utilizing a commercially available Cu-phosphite catalyst for the diastereoselective reductive coupling of chiral allenamides and ketones to afford chiral γ-lactone precursors in 80:20 to 99:1 dr.

Recent advances in Wacker oxidation: from conventional to modern variants and applications

Recent developments in the well-known Wacker oxidation process from conventional to modern variants and applications to natural products' synthesis are compiled in this review.

Synthesis of γ-Lactones by TBAI-Promoted Intermolecular Carboesterification of Carboxylic Acids with Alkenes and Alcohols

A novel tetrabutylammonium iodide (TBAI)-promoted three-component reaction of carboxylic acid with alkene and alcohol has been developed, which represents facile and straightforward access to polysubstituted γ-lactone skeletons in moderate-to-good yields. This methodology is distinguished by the use of a commercial catalyst and readily available starting materials, wide substrate scope, and operational simplicity. Mechanistic studies suggested that this transformation went through a radical process.

Palladium-Catalyzed Oxidation Reactions of Alkenes with Green Oxidants

Transition-metal-catalyzed oxidative functionalization of alkenes has emerged as a powerful and valuable tool in modern organic synthesis. Recently, many methods have been established for the assembly of C-C and C-heteroatom bonds, which provides tremendous possibility for application in biology, medicine, and materials science. However, the use of stoichiometric amounts of strong oxidants leads to poor selectivity, low atom economy, and a series of undesired waste products. By contrast, green oxidants, such as O₂ , H₂ O₂ , or tert-butyl hydroperoxide (TBHP), have bright prospects due to their attributes of mild, low cost, and great sustainability in transition-metal-catalyzed oxidation reactions. Based on the great and unique potential for the development of aerobic reactions, this review mainly highlights homogenous palladium-catalyzed green oxidations of alkenes that have been reported in recent years. These methods provide new strategies for the transformation and functionalization of alkenes; some of them have also been successfully applied to the synthesis of the core structures of drugs and natural products. Additionally, through in-depth studies of the reaction mechanisms in this field, it is believed that palladium-catalyzed green oxidation reactions of alkenes with O₂ , H₂ O₂ , or TBHP will create added value for organic synthetic chemistry.

trans-Diastereoselective Syntheses of γ-Lactones by Visible Light-Iodine-Mediated Carboesterification of Alkenes

This study aims to develop an intermolecular lactonization reaction of alkenes with carbonyls mediated by visible light and molecular iodine. The one-step reaction involved the carboesterification of alkenes to produce the corresponding lactones in moderate to good yield. It was also revealed that it is possible to control the diastereoselectivity of the reaction by altering the base used and the reaction conditions. When water was added as a solvent, the reaction resulted in the formation of lactones with trans-selectivity. A mechanistic investigation was undertaken and it was found that the reaction requires the generation of an iodine radical from molecular iodine, driven by visible light irradiation, and proceeds via the formation of an iodine radical alkene adduct. The proposed reaction is an example of a rare-metal free intermolecular addition cyclization reaction, which is an environment-friendly chemical process that only uses molecular iodine. In addition, since diastereoselectivity was observed without the use of any specific reagents, the developed methodology is an example of a novel stereoselective transformation using only cost-effective reagents.

Tandem cyclization of o-alkynylanilines with isocyanides triggered by intramolecular nucleopalladation: access to heterocyclic fused 2-aminoquinolines

Herein, a novel strategy for the synthesis of various heterocyclic fused 2-aminoquinolines via palladium-catalyzed tandem cyclization of o-alkynylanilines with isocyanides has been developed. This process includes trans-oxy/aminopalladation, isocyanide insertion, elimination and 1,3-hydrogen migration. Besides high atom and step economy, this method shows good functional group compatibility with excellent chemo- and regioselectivities under mild reaction conditions.

Copper catalyzed one-pot difluoroalkylation and lactonization of unsaturated carboxylic acids

A new cost-effective method for one-pot bifunctionalization of unsaturated carboxylic acids to afford difluoroalkylated γ-lactones has been reported using a Cu(i) catalyst.