Synthesis of Oxindoles via Iron-Mediated Hydrometallation-Cyclization ofN-Arylacrylamides

The Progress of Reductive Coupling Reaction by Iron Catalysis

The transition metal catalyzed coupling reaction has revolutionized the strategies for forging the carbon-carbon bonds. In contrast to traditional cross-coupling methods using pre-prepared nucleophilic organometallic reagents, reductive coupling reactions for the C-C bonds formation provide some advantages. Because both coupling partners are reduced in the final products using a stoichiometric amount of a reductant, this approach not only avoids the need to use sensitive organometallic species, but also provides an orthogonal and complementary access to classical coupling reaction. Notably, the reductive coupling reactions feature readily available fragments, promote good step economy, exhibit high functional group tolerance and unique chemoselectivity, which have propelled their increasingly popular in the organic synthesis. In recent years, due to the low price, minimal toxicity, and environmentally benign character, iron-catalyzed carbon-carbon coupling reactions have garnered significant attention from the organic synthetic chemists and pharmacologists, especially the iron-catalyzed reductive coupling. This review aims to provide an insightful overview of recent advances in iron-catalyzed reductive coupling reactions, and to illustrate their possible reaction mechanisms.

Radical-mediated photoredox hydroarylation with thiosulfonate

Herein, we report a novel visible light-induced photocatalytic system that enables intramolecular hydroarylation of unactivated alkenes. Thiosulfonate compounds were found to be the key radical precursor that mediates the Minisci-type intramolecular cyclization reaction. Under the optimal reaction conditions, a wide range of pyridyquinazolinone and pyrroloquinazolinone products were obtained in moderate to good yields.

Recent Developments in C–C Bond Formation Using Catalytic Reductive Coupling Strategies

Metal-catalyzed reductive coupling processes have emerged as a powerful methodology for the introduction of molecular complexity from simple starting materials. These methods allow for an orthogonal approach to that of redox-neutral strategies for the formation of C–C bonds by enabling cross-coupling of starting materials not applicable to redox-neutral chemistry. This short review summarizes the most recent developments in the area of metal-catalyzed reductive coupling utilizing catalyst turnover by a stoichiometric reductant that becomes incorporated in the final product.

1 Introduction

2 Ni Catalysis

3 Cu Catalysis

4 Ru, Rh, and Ir Catalysis

4.1 Alkenes

4.2 1,3-Dienes

4.3 Allenes

4.4 Alkynes

4.5 Enynes

5 Fe, Co, and Mn Catalysis

6 Conclusion and Outlook

An iodine-promoted one-pot and metal-free access to indolin-2-ones

A new method for the synthesis of indolin-2-ones has been realized by an I2-promoted oxidative reaction from 1,2,3,3-tetramethyl-3 H-indolium iodides. This transformation proceeded smoothly under metal-free and peroxide-free conditions in a cascade manner.

Ligand-Promoted Iron(III)-Catalyzed Hydrofluorination of Alkenes

An iron-catalyzed hydrofluorination of unactivated alkenes has been developed. The use of a multidentate ligand and the fluorination reagent N-fluorobenzenesulfonimide (NFSI) proved to be critical for this reaction, which afforded various fluorinated compounds in up to 94 % yield.

A tethering directing group strategy for ruthenium-catalyzed intramolecular alkene hydroarylation

We report a new catalyst design for N-heterocycle synthesis that utilizes an alkene-tethered amide moiety as a directing group for aromatic C-H activation. This tethering directing group strategy is demonstrated in a ruthenium-catalyzed intramolecular alkene hydroarylation with N-aryl acrylamides to form oxindole products.

Methods Utilizing First-Row Transition Metals in Natural Product Total Synthesis

First-row transition-metal-mediated reactions constitute an important and growing area of research due to the low cost, low toxicity, and exceptional synthetic versatility of these metals. Currently, there is considerable effort to replace existing precious-metal-catalyzed reactions with first-row analogs. More importantly, there are a plethora of unique transformations mediated by first-row metals, which have no classical second- or third-row counterpart. Herein, the application of first-row metal-mediated methods to the total synthesis of natural products is discussed. This Review is intended to highlight strategic uses of these metals to realize efficient syntheses and highlight the future potential of these reagents and catalysts in organic synthesis.

Mn-, Fe-, and Co-Catalyzed Radical Hydrofunctionalizations of Olefins

Cofactor-mimetic aerobic oxidation has conceptually merged with catalysis of syngas reactions to form a wide range of Markovnikov-selective olefin radical hydrofunctionalizations. We cover the development of the field and review contributions to reaction invention, mechanism, and application to complex molecule synthesis. We also provide a mechanistic framework for understanding this compendium of radical reactions.