Co-Catalyzed Cross-Coupling Reaction of Alkyl Fluorides with Alkyl Grignard Reagents

The cross-coupling reaction of unactivated alkyl fluorides with alkyl Grignard reagents by a CoCl₂/LiI/1,3-pentadiene catalytic system is described. The present reaction smoothly cleaved C–F bonds under mild conditions and achieved alkyl–alkyl cross-coupling even when sterically hindered tertiary alkyl Grignard reagents were employed. Since alkyl fluorides are inert toward many reagents and catalytic intermediates, the use of the present reaction enables a new multistep synthetic route to construct carbon frameworks by combining conventional transformations

Regioselective Cis Insertion of DMAD into Au–P Bonds: Effect of Auxiliary Ligands on the Reaction Mechanism

The cis insertion of dimethyl acetylenedicarboxylate (DMAD, <b>2</b>) into the Au–P bond of Au­(SAr)­(PAr′₃) (<b>1</b>) occurs selectively at room temperature to give adduct <b>3</b>, whose X-ray crystallographic analysis exhibits the predominant character of an alkenylphosphorus zwitterion complex. The first-order kinetics with respect to <b>1</b> and <b>2</b> and the large negative value of Δ<i>S</i>^⧧ indicate that the reaction proceeds through the coordination of <b>2</b> to <b>1</b> followed by a concerted inner-sphere nucleophilic attack of PPh₃ on the coordinated triple bond. In contrast, Au­(Cl)­(PPh₃) (<b>4</b>) does not react with <b>2</b> even at 60 °C. However, the tricoordinated 16-electron complex Au­(Cl)­(PPh₃)₂ (<b>5</b>) quite successfully reacts with <b>2</b> to produce insertion product <b>6</b>, demonstrating that two PPh₃ ligands are required for the reaction

Co-Catalyzed Cross-Coupling of Alkyl Halides with Tertiary Alkyl Grignard Reagents Using a 1,3-Butadiene Additive

The cobalt-catalyzed cross-coupling of alkyl (pseudo)­halides with alkyl Grignard reagents in the presence of 1,3-butadiene as a ligand precursor and LiI is described. Sterically congested quaternary carbon centers could be constructed by using tertiary alkyl Grignard reagents. This reaction proceeds via an ionic mechanism with inversion of stereochemistry at the reacting site of the alkyl halide and is compatible with various functional groups. The use of both 1,3-butadiene and LiI was essential for achieving high yields and high selectivities

Diarylrhodates as Promising Active Catalysts for the Arylation of Vinyl Ethers with Grignard Reagents

Anionic diarylrhodium complexes, generated by reacting [RhCl­(cod)]₂ with 2 equiv of aryl Grignard reagents, were found to be effective active catalysts in cross-coupling reactions of vinyl ethers with aryl Grignard reagents, giving rise to the production of vinyl arenes. In this catalytic system, vinyl-O bonds were preferably cleaved over Ar–O or Ar–Br bonds. A lithium rhodate complex was isolated, and its crystal structure was determined by X-ray crystallography

Copper-Catalyzed Alkyl–Alkyl Cross-Coupling Reactions Using Hydrocarbon Additives: Efficiency of Catalyst and Roles of Additives

Cross-coupling of alkyl halides with alkyl Grignard reagents proceeds with extremely high TONs of up to 1230000 using a Cu/unsaturated hydrocarbon catalytic system. Alkyl fluorides, chlorides, bromides, and tosylates are all suitable electrophiles, and a TOF as high as 31200 h^–1 was attained using an alkyl iodide. Side reactions of this catalytic system, i.e., reduction, dehydrohalogenation (elimination), and the homocoupling of alkyl halides, occur in the absence of additives. It appears that the reaction involves the β-hydrogen elimination of alkylcopper intermediates, giving rise to olefins and Cu–H species, and that this process triggers both side reactions and the degradation of the Cu catalyst. The formed Cu–H promotes the reduction of alkyl halides to give alkanes and Cu–X or the generation of Cu(0), probably by disproportionation, which can oxidatively add to alkyl halides to yield olefins and, in some cases, homocoupling products. Unsaturated hydrocarbon additives such as 1,3-butadiene and phenylpropyne play important roles in achieving highly efficient cross-coupling by suppressing β-hydrogen elimination, which inhibits both the degradation of the Cu catalyst and undesirable side reactions

Multicomponent Coupling Reaction of Perfluoroarenes with 1,3-Butadiene and Aryl Grignard Reagents Promoted by an Anionic Ni(II) Complex

An anionic Ni complex was isolated and its structure determined by X-ray crystallography. With such an anionic complex as a key intermediate, a regio- and stereoselective multicomponent coupling reaction of perfluoroarenes, aryl Grignard reagents, and 1,3-butadiene in a 1:1:2 ratio was achieved, resulting in the formation of 1,6-octadiene derivatives containing two aryl groups, one from the perfluoroarene and the other from the aryl Grignard reagent, at the 3- and 8-positions, respectively

σ‑Bond Metathesis between M–X and RC(O)X′ (M = Pt, Pd; X, X′ = Cl, Br, I): Facile Determination of the Relative Δ<i>G</i> Values of the Oxidative Additions of RC(O)X to an M(0) Complex, Evidence by Density Functional Theory Calculations, and Synthetic Applications

The novel utility of the ligand exchange reaction between M–X and RC­(O)­X′ (X, X′ = halogen; R = aryl, alkyl) is described. The relative Δ<i>G</i>s (ΔΔ<i>G</i>s) of the oxidative additions of acid halides RC­(O)­X to M­(PPh₃)₂L_<i>n</i> (M = Pt, Pd) were determined using the halogen-exchange reactions between X of <i>trans</i>-M­(X)­[C­(O)­R]­(PPh₃)₂ and X′ of RC­(O)­X′. Experimental thermodynamics data are reasonably consistent with those obtained by density functional theory (DFT) calculations. Activation parameters obtained by experiments as well as a systematic DFT study supported the fact that reactions occurred through slightly distorted quadrangular pentacoordinated σ-bond metatheses, in which the Cl atom underwent a more indirect course than the Br atom. Moreover, exchange reactions were employed as the accessible prototype for the conversion of halogen ligands of nickel triad complexes into heavier halogen ligands