Bimetallic Metal-Organic Coordination Polymers Facilitated the Selective C-F Cleavage of Polyfluoroarenes

Selective C-F bond cleavage of polyfluoroarenes has attracted tremendous interest due to its promising applications in introducing fluorinated building blocks into organic molecules. However, it remains a challenge to achieve highly site-selective C-F bond cleavage because of the intrinsic inertness of the C-F bond and the difficulty in distinguishing specific C-F bonds on the aromatic ring. Herein we report an efficient nucleophilic aromatic substitution (S_NAr) reaction of polyfluoroarenes with Grignard reagents that employs MnFe-based bimetallic metal-organic coordination polymers (MOCPs) as recyclable and reusable heterogeneous catalysts. Significantly, in this reaction, the prepared MOCP (Mn-Fe) catalyst exhibited excellent activity in selective C-F bond cleavage and afforded a series of functionalized polyfluoroarenes in moderate to excellent yields (up to 96%). This work highlights the potential of MOCP catalysts to serve as a tunable platform in Lewis acid catalysis.

Transition-Metal-Catalyzed Cross-Coupling Reactions of Grignard Reagents

Transition-metal-catalyzed cross-coupling of organo­halides, ethers, sulfides, amines, and alcohols (and derivatives thereof) with Grignard reagents, known as the Kumada–Tamao–Corriu reaction, can be used to prepare important intermediates in the synthesis of numerous­ biologically active compounds. The most frequently used transition metals are nickel, palladium, and iron, but there are several examples for cross-coupling reactions catalyzed by copper, cobalt, manganese, chromium, etc. salts and complexes. The aim of this review is to summarize the most important transition-metal-catalyzed cross-coupling reactions realized in the period 2000 to 2020.

1 Introduction

2 Nickel Catalysis

3 Palladium Catalysis

4 Iron Catalysis

5 Catalysis by Other Transition Metals

5.1 Cobalt Catalysis

5.2 Copper Catalysis

5.3 Manganese Catalysis

5.4 Chromium Catalysis

6 Conclusion

Generation and Reactivity of Amidyl Radicals: Manganese-Mediated Atom-Transfer Reaction

A simple and efficient protocol to generate amidyl radicals from amine functionalities through a manganese-mediated atom-transfer reaction has been developed. This approach employs an earth-abundant and inexpensive manganese complex, Mn₂ (CO)₁₀ , as the catalyst and visible light as the energy input. Using this strategy, site-selective chlorination of unactivated C(sp³ )-H bonds of aliphatic amines and intramolecular/intermolecular chloroaminations of unactivated alkenes were readily realized under mild reaction conditions, thus providing efficient access to a range of synthetically valuable alkyl chlorides, chlorinated pyrrolidines, and vicinal chloroamine derivatives. These practical reactions exhibit a broad substrate scope and tolerate a wide array of functional groups, and complex molecules including various marketed drug derivatives.

Aerobic and Ligand-Free Manganese-Catalyzed Homocoupling of Arenes or Aryl Halides via in Situ Formation of Aryllithiums

Ligand-free manganese-catalyzed homocoupling of arenes or aryl halides can be carried out under aerobic conditions via the in situ formation of the corresponding aryllithiums. A wide range of biaryls and derivatives has been obtained, and a mechanism involving monomeric manganese-oxo complexes has been proposed on the basis of DFT calculations.

Catalytic reductive [4 + 1]-cycloadditions of vinylidenes and dienes

Cycloaddition reactions provide direct and convergent routes to cycloalkanes, making them valuable targets for the development of synthetic methods. Whereas six-membered rings are readily accessible from Diels-Alder reactions, cycloadditions that generate five-membered rings are comparatively limited in scope. Here, we report that dinickel complexes catalyze [4 + 1]-cycloaddition reactions of 1,3-dienes. The C₁ partner is a vinylidene equivalent generated from the reductive activation of a 1,1-dichloroalkene in the presence of stoichiometric zinc. Intermolecular and intramolecular variants of the reaction are described, and high levels of asymmetric induction are achieved in the intramolecular cycloadditions using a C ₂-symmetric chiral ligand that stabilizes a metal-metal bond.

An Active Palladium Colloidal Catalyst for the Selective Oxidative Heterocoupling of (Hetero)Aryl Boronic Acids

A highly selective oxidative heterocoupling protocol for (hetero)aryl boronic acids with an active palladium colloidal catalyst was developed. The judicious choice of electronically different aryl boronic acids made possible such couplings under mild conditions, with air as oxidant, while embracing a wide substrate scope. This successful approach further allowed the development of a unique one-pot sequential oxidative heterocoupling/Suzuki-Miyaura cross-coupling tandem process for accessing substituted terphenyls.

Antitubercular Bis-Substituted Cyclam Derivatives: Structure-Activity Relationships and in Vivo Studies

We recently reported the discovery of nontoxic cyclam-derived compounds that are active against drug-resistant Mycobacterium tuberculosis. In this paper we report exploration of the structure-activity relationship for this class of compounds, identifying several simpler compounds with comparable activity. The most promising compound identified, possessing significantly improved water solubility, displayed high levels of bacterial clearance in an in vivo zebrafish embryo model, suggesting this compound series has promise for in vivo treatment of tuberculosis.

Active Palladium Colloids via Palladacycle Degradation as Efficient Catalysts for Oxidative Homocoupling and Cross-Coupling of Aryl Boronic Acids

Active palladium colloids formed upon degradation of a palladacyclic complex (Herrmann-Beller 1) have been isolated for the first time and thoroughly characterized with techniques such as transmission electron microscopy (TEM), high-resolution TEM, X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure spectroscopy. The synthesized palladium colloids have been utilized as efficient catalysts for the oxidative homocoupling of aryl boronic acids. Cross-coupling of two different aryl boronic acids has also been made possible using these active palladium colloids. This is the first report of this kind of coupling between aryl boronic acids.

Manganese-mediated/-catalyzed oxidative carboazidation of acrylamides

Manganese-mediated/-catalyzed oxidative carboazidation of acrylamides was developed for the synthesis of various azido oxindoles.

Quinonediimines as redox-active organocatalysts for oxidative coupling of aryl- and alkenylmagnesium compounds under molecular oxygen

N,N′-Diphenyl-p-benzoquinonediimine worked as a redox-active organocatalyst for the oxidative homo-coupling of aryl- and alkenylmagnesium compounds under molecular oxygen.

Unified Protocol for Cobalt-Catalyzed Oxidative Assembly of Two Aryl Metal Reagents Using Oxygen as an Oxidant

The first cobalt-catalyzed oxidative cross-coupling reaction of two aryl metal reagents is described. An equivalent amount of two aryl Grignard or lithium reagents, after mediation by an equivalent amount of simple ClTi(OEt)3, was facilely assembled under the catalysis of 1 mol % of CoCl2/10 mol % of DMPU using oxygen. The cross-couplings between various aryl metal reagents, especially between two structurally similar aryl Grignard reagents, proceeded smoothly and selectively and, thus, provided a highly general and efficient method for the construction of biaryl compounds.

Iron catalyzed oxidative assembly of N-heteroaryl and aryl metal reagents using oxygen as an oxidant

An equivalent amount of N-heteroaryl and aryl Grignard or lithium reagents, after mediation by an equivalent of titanate, was facilely coupled to furnish N-heteroaryl-aryl compounds under the catalysis of FeCl3/TMEDA at ambient temperature using oxygen as an oxidant. Most of the common N-heteroaryls were all good candidates, and thus provided a general, green and pratical protocol for the flexible construction of various N-heteroaryl-aryl structures.

Iron-catalyzed oxidative biaryl cross-couplings via mixed diaryl titanates: significant influence of the order of combining aryl Grignard reagents with titanate

Two highly structurally similar aryl Grignard reagents were oxidatively cross-coupled via diaryl titanates in the catalysis of iron using oxygen.

Progress and developments in the turbo Grignard reagent i-PrMgCl·LiCl: a ten-year journey

The structural and kinetic perspectives of i-PrMgCl·LiCl help to rationalize the trends of its unique reactivity and selectivity.

Copper-catalyzed oxidative homo- and cross-coupling of Grignard reagents using diaziridinone

Transition-metal-catalyzed cross-coupling reactions are among the most powerful synthetic transformations. This paper describes an efficient copper-catalyzed homo- and cross-coupling of Grignard reagents with di-tert-butyldiaziridinone as oxidant under mild conditions, giving the coupling products in good to excellent yields. The reaction process has a broad substrate scope and is also effective for the C(sp)-C(sp(3)) coupling.

The transition-metal-catalyst-free oxidative homocoupling of organomanganese reagents prepared by the insertion of magnesium into organic halides in the presence of MnCl2·2LiCl

Organomanganese reagents were prepared by the insertion of magnesium into aryl halides in the presence of MnCl2·2LiCl. These organomanganese reagents smoothly undergo 1,2-addition, acylation, and Pd-catalyzed cross-coupling with various electrophiles. Especially, the oxidative homocoupling of organomanganese reagents was completed in one pot without an additional transition-metal catalyst.

Palladium-catalyzed desulfitative arylation by C-O bond cleavage of aryl triflates with sodium arylsulfinates

An efficient Pd-catalyzed desulfitative coupling reaction of sodium arylsulfinates as arylation reagents by C-O bond cleavage of aryl triflates was developed. With only 2 mol % of Pd(OAc)(2) as catalyst and XPhos as ligand, the reaction proceeded well for a range of substrates.

Synthetic scope, computational chemistry and mechanism of a base induced 5-endo cyclization of benzyl alkynyl sulfides

We present an experimental and computational study of the reaction of aryl substituted benzyl 1-alkynyl sulfides with potassium alkoxide in acetonitrile, which produces 2-aryl 2,3-dihydrothiophenes in poor to good yields. The cyclization is most efficient with electron withdrawing groups on the aromatic ring. Evidence indicates there is rapid exchange of protons and tautomerism of the alkynyl unit prior to cyclization. Theoretical calculations were also conducted to help rationalize the base induced 5-endo cyclization of benzyl 1-propynyl sulfide (1a). The potential energy surface was calculated for the formation of 2,3-dihydrothiophene in a reaction of benzyl 1-propynyl sulfide (1a) with potassium methoxide. Geometries were optimized with CAM-B3LYP/6-311+G(d,p) in acetonitrile with the CPCM solvent model. It is significant that the benzyl propa-1,2-dien-1-yl sulfane (6) possessed a lower benzylic proton affinity than the benzyl prop-2-yn-1-yl sulfane (8) thus favoring the base induced reaction of the former. From benzyl(propa-1,2-dien-1-yl sulfane (6), 2,3-dihydrothiophene can be formed via a conjugate base that undergoes 5-endo-trig cyclization followed by a protonation step.