Ligand-Free Reusable Palladium-Catalyzed Heck-Type Coupling Reactions of Hypervalent Iodine Reagents under Mild Conditions

Palladium-Catalyzed Organic Reactions Involving Hypervalent Iodine Reagents

The chemistry of polyvalent iodine compounds has piqued the interest of researchers due to their role as important and flexible reagents in synthetic organic chemistry, resulting in a broad variety of useful organic molecules. These chemicals have potential uses in various functionalization procedures due to their non-toxic and environmentally friendly properties. As they are also strong electrophiles and potent oxidizing agents, the use of hypervalent iodine reagents in palladium-catalyzed transformations has received a lot of attention in recent years. Extensive research has been conducted on the subject of C—H bond functionalization by Pd catalysis with hypervalent iodine reagents as oxidants. Furthermore, the iodine(III) reagent is now often used as an arylating agent in Pd-catalyzed C—H arylation or Heck-type cross-coupling processes. In this article, the recent advances in palladium-catalyzed oxidative cross-coupling reactions employing hypervalent iodine reagents are reviewed in detail.

Hypervalent Iodine Reagents in Palladium-Catalyzed Oxidative Cross-Coupling Reactions

Hypervalent iodine compounds are valuable and versatile reagents in synthetic organic chemistry, generating a diverse array of useful organic molecules. Owing to their non-toxic and environmentally friendly features, these reagents find potential applications in various oxidative functionalization reactions. In recent years, the use of hypervalent iodine reagents in palladium-catalyzed transformations has been widely studied as they are strong electrophiles and powerful oxidizing agents. For instance, extensive work has been carried out in the field of C–H bond functionalization via Pd-catalysis using hypervalent iodine reagents as oxidants. In addition, nowadays, iodine(III) reagents have been frequently employed as arylating agents in Pd-catalyzed C–H arylation or Heck-type cross-coupling reactions. In this review, recent advancements in the area of palladium-catalyzed oxidative cross-coupling reactions using hypervalent iodine reagents are summarized in detail.

Recent Advances Utilized in the Recycling of Homogeneous Catalysis

Homogeneous catalysts often show high activity and selectivity towards the various chemical transformations. Most of the transition metal-based active catalysts are expensive, rare, and have strict regulations for their use in pharmaceutical products. Hence, there is a requirement to develop suitable technologies for the practical separation and recycling of metal complex catalysts along with the sustainability of the process. This review focuses on the recent techniques used for the catalyst separation, their recovery, and recyclability of the homogeneous form of catalysts based on their economic compatibility and industrial applications. Various homogeneous catalysts have been reviewed on the basis of their support or media, active centres and recyclability aspects of the catalysts. This review gives brief insights into the varied examples of different recycling techniques utilized in the past 6-7 years.

o-Iodoxybenzoic acid mediated generation of aryl free radicals: synthesis of stilbenes through C–C cross-coupling with β-nitrostyrenes

The generation of an aryl free radicals in the presence of nitrostyrenes through a combination of aryl hydrazines and o-iodoxybenzoic acid led to the synthesis of stilbenes by forming a new carbon–carbon bond after subsequent elimination of a nitrosyl radical.

Advances in Synthetic Applications of Hypervalent Iodine Compounds

The preparation, structure, and chemistry of hypervalent iodine compounds are reviewed with emphasis on their synthetic application. Compounds of iodine possess reactivity similar to that of transition metals, but have the advantage of environmental sustainability and efficient utilization of natural resources. These compounds are widely used in organic synthesis as selective oxidants and environmentally friendly reagents. Synthetic uses of hypervalent iodine reagents in halogenation reactions, various oxidations, rearrangements, aminations, C-C bond-forming reactions, and transition metal-catalyzed reactions are summarized and discussed. Recent discovery of hypervalent catalytic systems and recyclable reagents, and the development of new enantioselective reactions using chiral hypervalent iodine compounds represent a particularly important achievement in the field of hypervalent iodine chemistry. One of the goals of this Review is to attract the attention of the scientific community as to the benefits of using hypervalent iodine compounds as an environmentally sustainable alternative to heavy metals.