Nickel-catalyzed alkoxycarbonylation of aryl iodides with 1 atm CO

Electrochemical Synergistic Ni/Co-Catalyzed Carbonylative Cross-Electrophile Coupling of Aryl and Alkyl Halides with CO

Accessing unsymmetric ketones and achieving their carbon isotope labeling are crucial yet challenging tasks in both synthetic and medicinal chemistry. We report here an efficient electrochemical nickel-/cobalt-catalyzed carbonylative cross-electrophile coupling reaction. This method allows for the modular synthesis of a library of unsymmetric ketones from simple building blocks, including aryl halides, alkyl halides, and gaseous CO. The simultaneous use of nickel and cobalt salts as concerted catalysts ensures the high efficiency of this three-component carbonylative coupling. Furthermore, electrochemical reduction avoids the use of stoichiometric reductants, making this protocol more sustainable and attractive. The broad substrate scope and late-stage 13C isotope labeling of complex molecules derived from biologically active compounds highlight the practicality of this method.

Current-Regulated Selective Nickel-Catalyzed Electroreductive Cross-Electrophile Carbonylation to β/γ-Hydroxy Ketones

The nickel catalyzed multi-component cross-electrophile carbonylation which emerges as a powerful and efficient method for constructing diverse ketones has attracted increasing attention of organic chemists. However, the selectivity of this reaction poses a significant challenge. In this work, we have developed a current-regulated selective nickel-catalyzed electroreductive cross-electrophile carbonylation, which offers a direct convergent synthesis of β/γ-hydroxy ketones, which represent pivotal structural motifs found in numerous natural products, bioactive molecules, pharmaceutical compounds, and essential building blocks. A diverse range of multi-substituted β/γ-hydroxyketones can be accessed with high chemo- and regioselectivity from epoxides, aryl iodides, and a simple CO source (ClCO2Pr). This electroreductive carbonylation strategy exhibits high functional group tolerance and can be applied in late-stage derivatization of drugs and natural products. Notably, chiral epoxides can be employed as reactants with chirality retention, enabling the synthesis of asymmetric β-hydroxy ketones. Our approach demonstrates a novel electrochemical selectivity-controlled strategy in multi-component cross-electrophile coupling.

Palladium-Catalyzed Three-Component Cascade Carbonylation Reaction to Construct Benzofuran Derivatives

A novel three-component cyclization carbonylation reaction of iodoarene-tethered propargyl ethers with amine and CO is reported. This palladium-catalyzed cascade reaction undergoes a sequence of oxidative addition, unsaturated bond migration, carbonyl insertion, and nucleophilic attack to deliver the benzofuran skeleton. Both aromatic amines and aliphatic amines could proceed smoothly in this transformation under one atm of CO.

Nickel-Catalyzed Carbonylative Negishi Cross-Coupling of Unactivated Secondary Alkyl Electrophiles with 1 atm CO Gas

We describe a nickel-catalyzed carbonylative cross-coupling of unactivated secondary alkyl electrophiles with the organozinc reagent at atmospheric CO gas, thus allowing the expedient construction of unsymmetric dialkyl ketones with broad functional group tolerance. The leverage of a newly developed NN2-pincer type ligand enables the chemoselective three-component carbonylation by overcoming the competing Negishi coupling, the undesired β-hydride elimination, and dehalogenation of alkyl iodides side pathways. Both alkyl iodides and alkyl tosylates are compatible in the single electron transfer involved mechanism.

Nickel-catalyzed acylzincation of allenes with organozincs and CO

Transition metal-catalyzed carbonylative reaction with CO gas are among the central task in organic synthesis, enabling the construction of highly valuable carbonyl compound. Here, we show an earth-abundant nickel-catalyzed three-component tandem acylzincation/cyclization sequence of allene and alkylzinc reagent with 1 atm of CO under mild conditions. This protocol is featured by broad functional group tolerance with high reaction selectivity, providing a rapid and convenient synthetic method for the construction of diverse fully substituted benzotropone derivatives. Mechanistic studies reveal that the installation of a cyano group tethered to allene moiety enables the high regio- and stereoselectivity of this acylzincation of allene, allowing the selective formation of three consecutive C-C bonds in a highly efficient manner.

Mechanistic Insight into Palladium/Brønsted Acid Catalyzed Methoxycarbonylation and Hydromethoxylation of Internal Alkene: A Computational Study

Density functional theory (DFT) calculations were performed to study the palladium/Brønsted acid-catalyzed methoxycarbonylation and hydromethoxylation reactions of internal alkene. The calculated results show that the pyridyl group (N atom) in bidentate phosphine ligand with built-in base (L1) plays a crucial role in controlling the selectivity. With the help of the pyridyl group, the methanolysis steps in the methoxycarbonylation reaction and the hydromethoxylation reaction become easy, and both the linear ester methyl 3,4-dimethylpentanoate (P1) and the hydromethoxylation product 2-methoxy-2,3-dimethylbutane (P2) could be obtained. In contrast, the possibility of leading to branched ester P1' was ruled out according to our calculations. The steric effect could account for the observed selectivity. In the presence of the DPEphos ligand (L2) that does not bear the pyridyl group, the methanolysis step in the methoxycarbonylation reaction becomes the rate-determining step with a high overall energy barrier. Neither linear nor branched methoxycarbonylation product could be generated. The palladium/Brønsted acid co-catalyzed hydromethoxylation also become difficult without the assistance of the pyridyl group in the presence of the L2 ligand. Instead, TsOH-catalyzed hydromethoxylation reaction could take place to generate the ether product P2.

Nickel-Catalyzed Aminocarbonylation of Aryl Iodides with 1 atm CO

Reported here is a nickel-catalyzed aminocarbonylation of aromatic iodides with (hetero)aryl anilines and alkyl amines under atmospheric CO pressure. The reaction features with broad substrate scope with excellent functional group tolerance, providing an expedient method for the construction of amide analogues. Notably, amino alcohols can be selectively transformed into the corresponding amides successfully without interfering the hydroxyl group under the current standard conditions.

Synthesis of Novel Cavitand Host Molecules via Palladium-Catalyzed Aryloxy- and Azidocarbonylation

Novel, elongated, resorcine[4]arene-based cavitands were synthesized via various consecutive reaction steps, including homogeneous catalytic aryloxy- and azidocarbonylation processes. The effects of carbon monoxide pressure and temperature on the conversion were examined in aryloxycarbonylation. It was revealed that a reaction temperature of 100 °C is required to achieve complete conversion both with monodentate (PPh₃) and bidentate (Xantphos) phosphines at different carbon monoxide pressures (1-40 bar). Using ten different phenols as O-nucleophiles, partial hydrolysis of the esters to the corresponding carboxylic acids took place-i.e., 58-90% chemoselectivities toward esters were obtained. Moreover, the influences of temperature, reaction time and the catalyst ratio on the selectivity and conversion were described in the case of azidocarbonylation reaction. The formation of the acyl azide with high chemoselevtivity can be achieved at room temperature only. The higher reaction temperatures (50 °C) and higher catalyst loadings favor the formation of the primary amide. The characterization of the target compounds (esters and acyl azides) was carried out by IR and ¹H and ¹3C NMR. The discussion of the influences of various parameters is based on in situ NMR investigations.

Oxidative C-H/N-H Carbonylation of Benzamide by Nickel Catalysis with CO as the Carbonyl Source

An efficient and direct carbonylation of aminoquinoline benzamides has been developed using abundant and inexpensive Ni(OAc)₂·4H₂O as the catalyst and carbon monoxide as a cost-efficient C1 building block. This process features good functional-group tolerance and can be conducted on gram scale. The directing group can be easily removed under mild conditions.

Palladium-catalyzed Heck cyclization/carbonylation with formates: synthesis of azaindoline-3-acetates and furoazaindolines

We report herein a palladium-catalyzed domino cyclization/carbonylation to access ester-functionalized azaindolines, applying formates as a convenient carbonyl source. All four azaindoline isomers were constructed, exhibiting good functional group compatibility. On this basis, modifying the starting tether on the aminopyridine led to furoazaindolines via an intramolecular reductive cyclization after the palladium-catalyzed process.

Nickel-Catalyzed Carbonylative Synthesis of α,β-Unsaturated Thioesters from Vinyl Triflates and Arylsulfonyl Chlorides

A straightforward and efficient synthesis of α,β-unsaturated thioesters has been developed via a nickel-catalyzed thiocarbonylation reaction of vinyl triflates with arylsulfonyl chlorides. With Mo(CO)₆ as both CO source and reductant, a variety of α,β-unsaturated thioesters were obtained in moderate to good yields with very good functional group compatibility. It is noteworthy that the present method is the first example on nickel-catalyzed carbonylative synthesis of α,β-unsaturated thioesters by using arylsulfonyl chlorides as the coupling partner.