Iron-Catalyzed Cross-Coupling of Functionalized Benzylmanganese Halides with Alkenyl Iodides, Bromides, and Triflates

Formal Cross-Coupling of Amines and Carboxylic Acids to Form sp3-sp2 Carbon-Carbon Bonds

Amines and carboxylic acids are abundant synthetic building blocks that are classically united to form an amide bond. To access new pockets of chemical space, we are interested in the development of amine-acid coupling reactions that complement the amide coupling. In particular, the formation of carbon-carbon bonds by formal deamination and decarboxylation would be an impactful addition to the synthesis toolbox. Here, we report a formal cross-coupling of alkyl amines and aryl carboxylic acids to form C(sp³)-C(sp²) bonds following preactivation of the amine-acid building blocks as a pyridinium salt and N-acyl-glutarimide, respectively. Under nickel-catalyzed reductive cross-coupling conditions, a diversity of simple and complex substrates are united in good to excellent yield, and numerous pharmaceuticals are successfully diversified. High-throughput experimentation was leveraged in the development of the reaction and the discovery of performance-enhancing additives such as phthalimide, RuCl₃, and GaCl₃. Mechanistic investigations suggest phthalimide may play a role in stabilizing productive Ni complexes rather than being involved in oxidative addition of the N-acyl-imide and that RuCl₃ supports the decarbonylation event, thereby improving reaction selectivity.

Recent Advances in Alkenyl sp2 C-H and C-F Bond Functionalizations: Scope, Mechanism, and Applications

Alkenes and their derivatives are featured widely in a variety of natural products, pharmaceuticals, and advanced materials. Significant efforts have been made toward the development of new and practical methods to access this important class of compounds by selectively activating the alkenyl C(sp²)-H bonds in recent years. In this comprehensive review, we describe the state-of-the-art strategies for the direct functionalization of alkenyl sp² C-H and C-F bonds until June 2022. Moreover, metal-free, photoredox, and electrochemical strategies are also covered. For clarity, this review has been divided into two parts; the first part focuses on currently available alkenyl sp² C-H functionalization methods using different alkene derivatives as the starting materials, and the second part describes the alkenyl sp² C-F bond functionalization using easily accessible gem-difluoroalkenes as the starting material. This review includes the scope, limitations, mechanistic studies, stereoselective control (using directing groups as well as metal-migration strategies), and their applications to complex molecule synthesis where appropriate. Overall, this comprehensive review aims to document the considerable advancements, current status, and emerging work by critically summarizing the contributions of researchers working in this fascinating area and is expected to stimulate novel, innovative, and broadly applicable strategies for alkenyl sp² C-H and C-F bond functionalizations in the coming years.

Iron-Catalyzed Cross-Coupling of Thioesters and Organomanganese Reagents

We report a Fukuyama-type coupling of thioesters with aliphatic organomanganese reagents utilizing a cheap and easily available iron(III) precatalyst. The reactions exhibit a wide tolerance of solvents and functional groups, allowing for the conversion of thioesters derived from natural products and pharmaceutical compounds. A strong steric impact from each reaction component (carboxylic moiety, thiol substituent and manganese reagent) was displayed, which enabled regioselective transformation of dithioesters. Mechanistic investigations showed that the released thiolate does not act as a mere spectator ligand, but rather positively influences the stability of intermediate alkyl(II)ferrates.

The crucial and multifaceted roles of main-group cations and their salts in iron-mediated cross-couplings

While a broad variety of iron-catalyzed cross-couplings involve the use of main-group organometallics R-[M] as nucleophiles, the role of the [M]ⁿ⁺ cation in the coupling process is generally disregarded. However, several beneficial effects of [M]ⁿ⁺ cations by themselves or involved in ionic salts used as additives have been observed in such procedures. At the molecular level, interaction of those [M]ⁿ⁺ cations with on-cycle organoiron intermediates can proceed in several ways. Intermolecular interactions can be observed, and also the implication of [M]ⁿ⁺ in the iron's first or second coordination sphere, e.g. by ambiphilic coordination of a [M]-X salt to an R-[Fe] bond. The use of [M]ⁿ⁺ cations in the reaction medium is also a powerful strategy enabling control of the distribution of iron oxidation states within the coupling process.

Organic synthesis with the most abundant transition metal–iron: from rust to multitasking catalysts

The promising aspects of iron in synthetic chemistry are being explored for three-four decades as a green and eco-friendly alternative to late transition metals. This present review unveils these rich iron-chemistry towards different transformations.

Recent Progress in Utilization of Functionalized Organometallic Reagents in Cross Coupling Reactions and Nucleophilic Additions

Organometallic compounds have become increasingly important in organic synthesis because of their high chemoselectivity and excellent reactivity. Recently, a variety of organometallic reagents were found to facilitate transition-metal-catalyzed cross-coupling reactions and nucleophilic addition reactions. Here, we have summarized the latest progress in cross-coupling reactions and in nucleophilic addition reactions with functionalized organometallic reagents present to illustrate their application value. Due to the tremendous contribution made by the Knochel group towards the development of novel organometallic reagents, this review draws extensively from their work in this area in recent years.

Introduction

1 Transition-Metal-Catalyzed Cross Couplings Involving Organo­zinc Reagents

2 Transition-Metal-Catalyzed Cross Couplings Involving Organomagnesium Reagents

3 Transition-Metal-Free Cross Couplings Involving Zn and Mg ­Organometallic Reagents

4 Nucleophilic Additions Involving Zn and Mg Organometallic Reagents

5 Cross-Coupling Reactions or Nucleophilic Additions Involving Mn, Al-, La-, Li-, Sm- and In-Organometallics

6 Conclusion

Iron-Catalyzed Cross-Coupling of Bis-(aryl)manganese Nucleophiles with Alkenyl Halides: Optimization and Mechanistic Investigations

Various substituted bis-(aryl)manganese species were prepared from aryl bromides by one-pot insertion of magnesium turnings in the presence of LiCl and in situ trans-metalation with MnCl₂ in THF at −5 °C within 2 h. These bis-(aryl)manganese reagents undergo smooth iron-catalyzed cross-couplings using 10 mol% Fe(acac)₃ with various functionalized alkenyl iodides and bromides in 1 h at 25 °C. The aryl-alkenyl cross-coupling reaction mechanism was thoroughly investigated through paramagnetic ¹H-NMR, which identified the key role of tris-coordinated ate-iron(II) species in the catalytic process.

Iron catalyzed stereoselective alkene synthesis: a sustainable pathway

Replacing expensive or toxic transition metals with iron has become an important trend. This article summarises the recent progresses of a wide range of Fe-catalyzed reactions for accessing various stereodefined alkenes.