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...

Advances in Synthetic Applications of Hypervalent Iodine Compounds

Research and industrial interest in radical C–H activation/radical cross-coupling chemistry has continuously grown over the past few decades. These reactions offer fascinating and unconventional approaches toward connecting molecular fragments with high atom- and step-economy that are often complementary to traditional methods. Success in this area of research was made possible through the development of photocatalysis and first-row transition metal catalysis along with the use of peroxides as radical initiators. This Review provides a brief and concise overview of the current status and latest methodologies using radicals or radical cations as key intermediates produced via radical C–H activation. This Review includes radical addition, radical cascade cyclization, radical/radical cross-coupling, coupling of radicals with M–R groups, and coupling of radical cations with nucleophiles (Nu).

Recent Advances in Radical C-H Activation/Radical Cross-Coupling.

Oxidative Coupling between Two Hydrocarbons: An Update of Recent C–H Functionalizations

Beijing National Laboratory of Molecular Sciences (BNLMS) and Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry and Green Chemistry Center, Peking University, 202 Chengfu Road, 098#, Beijing 100871, China State Key Laboratory of Organometallic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 200060, China

Transition-Metal-Free Coupling Reactions

Conventional methods for carrying out carbon–hydrogen functionalization and carbon–nitrogen bond formation are typically conducted at elevated temperatures, and rely on expensive catalysts as well as the use of stoichiometric, and perhaps toxic, oxidants. In this regard, electrochemical synthesis has recently been recognized as a sustainable and scalable strategy for the construction of challenging carbon–carbon and carbon–heteroatom bonds. Here, electrosynthesis has proven to be an environmentally benign, highly effective and versatile platform for achieving a wide range of nonclassical bond disconnections via generation of radical intermediates under mild reaction conditions. This review provides an overview on the use of anodic electrochemical methods for expediting the development of carbon–hydrogen functionalization and carbon–nitrogen bond formation strategies. Emphasis is placed on methodology development and mechanistic insight and aims to provide inspiration for future synthetic applications in the field of electrosynthesis.

/pdf/electrochemical-strategies-for-c-h-functionalization-and-c-n-13193n0ty2.pdf

Electrochemical strategies for C-H functionalization and C-N bond formation.

Metal‐Free Oxidative Carbon‐Heteroatom Bond Formation Through C–H Bond Functionalization

A range of heterocyclic ketone derivatives are synthesized by a novel, metal-free cross-dehydrogenative coupling between heterocycles and aldehydes under mild reaction conditions that are not sensitive to moisture.

Metal-Free Cross-Dehydrogenative Coupling of Heterocycles with Aldehydes

This new method for the oxidative radical azidation of alkenes relies on an azide in combination with a hypervalent iodine reagent.

Metal-free radical azidoarylation of alkenes: rapid access to oxindoles by cascade C-N and C-C bond-forming reactions.

The formation of C-C bonds embodies the core of organic chemistry because of its fundamental application in generation of molecular diversity and complexity. C-C bond-forming reactions are well-known challenges. To achieve this goal through direct functionalization of C-H bonds in both of the coupling partners represents the state-of-the-art in organic synthesis. Oxidative C-C bond formation obviates the need for prefunctionalization of both substrates. This Minireview is dedicated to the field of C-C bond-forming reactions through direct C-H bond functionalization under completely metal-free oxidative conditions. Selected important developments in this area have been summarized with representative examples and discussions on their reaction mechanisms.

Metal-Free Oxidative C-C Bond Formation through C-H Bond Functionalization.

A novel annulation reaction between 2-aminopyridine derivatives and arenes under metal-free conditions is described. The presented intermolecular transformation provided straightforward access to the important pyrido[1,2-a]benzimidazole scaffold under mild reaction conditions. The unprecedented application of the methyl group of methylbenzenes as a traceless, non-chelating, and highly regioselective directing group is reported.

Kiran Matcha

Papers

Metal‐Free Oxidative Carbon‐Heteroatom Bond Formation Through C–H Bond Functionalization

Metal-Free Cross-Dehydrogenative Coupling of Heterocycles with Aldehydes

Metal-free radical azidoarylation of alkenes: rapid access to oxindoles by cascade C-N and C-C bond-forming reactions.

Metal-Free Oxidative C-C Bond Formation through C-H Bond Functionalization.

Metal-Free Annulation of Arenes with 2-Aminopyridine Derivatives: The Methyl Group as a Traceless Non-Chelating Directing Group**