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We report a method for palladium-catalysed chain-running isomerization of terminal and internal alkenes. Using an air-stable 2,9-dimethylphenanthroline-palladium catalyst in combination with NaBAr4 promoter, olefins are converted to the most stable double bond isomer at −30 to 20 °C. Silyl enol ethers are readily formed from silylated allylic alcohols. Fluorinated substituents are compatible with the reaction conditions, allowing the synthesis of fluoroenolates. Catalyst loading as low as 0.05% can be employed on a gram scale. [ABSTRACT FROM AUTHOR]

We have developed a method for palladium-catalyzed, pyrazole-directed sp3 C−H bond arylation by aryl iodides. The reaction employs a Pd(OAc)2 catalyst at 5-10 mol % loading and silver(I) oxide as a halide-removal agent, and it proceeds in acetic acid or acetic acid/hexafluoroisopropanol solvent. Ozonolysis of the pyrazole moiety affords pharmaceutically important β-phenethylamines. [ABSTRACT FROM AUTHOR]

The palladium diphosphine complex 4 converts ethylene to hyperbranched unsaturated oligomers (Mn ≈ 330 g/mol) at 22 °C. In addition to the high stability of this catalyst observed at temperatures up to 75 °C, an increase of the reaction temperature leads to a decrease in branching densities of the oligomers, in sharp contrast to the palladium and nickel diimine catalyst systems. One-pot oligomerizations/hydrogenations were carried out to form hyperbranched saturated oligomers. [ABSTRACT FROM AUTHOR]

Conspectus: In recent years, carbon-hydrogen bond functionalization has evolved from an organometallic curiosity to a tool used in mainstream applications in the synthesis of complex natural products and drugs. The use of C-H bonds as a transformable functional group is advantageous because these bonds are the most abundant functionality in organic molecules. One-step conversion of these bonds to the desired functionality shortens synthetic pathways, saving reagents, solvents, and labor. Less chemical waste is generated as well, showing that this chemistry is environmentally beneficial. This Account describes the development and use of bidentate, monoanionic auxiliaries for transition-metal-catalyzed C-H bond functionalization reactions. The chemistry was initially developed to overcome the limitations with palladium-catalyzed C-H bond functionalization assisted by monodentate directing groups. By the use of electron-rich bidentate directing groups, functionalization of unactivated sp³ C-H bonds under palladium catalysis has been developed. Furthermore, a number of abundant base-metal complexes catalyze functionalization of sp² C-H bonds. At this point, aminoquinoline, picolinic acid, and related compounds are among the most used and versatile directing moieties in C-H bond functionalization chemistry. These groups facilitate catalytic functionalization of sp² and sp³ C-H bonds by iron, cobalt, nickel, copper, ruthenium, rhodium, and palladium complexes. Exceptionally general reactivity is observed, enabling, among other transformations, direct arylation, alkylation, fluorination, sulfenylation, amination, etherification, carbonylation, and alkenylation of carbon-hydrogen bonds. The versatility of these auxilaries can be attributed to the following factors. First, they are capable of stabilizing high oxidation states of transition metals, thereby facilitating the C-H bond functionalization step. Second, the directing groups can be removed, enabling their use in synthesis and functionalization of natural products and medicinally relevant substances. While the development of these directing groups presents a significant advance, several limitations of this methodology are apparent. The use of expensive second-row transition metal catalysts is still required for efficient sp³ C-H bond functionalization. Furthermore, the need to install and subsequently remove the relatively expensive directing group is a disadvantage. [ABSTRACT FROM AUTHOR]

A method for five- and six-membered heterocycle formation by palladium-catalyzed C-H/N-H coupling is presented. The method employs a picolinamide directing group, PhI(OAc)2 oxidant, and toluene solvent at 80-120 °C. Cyclization is effective for sp² as well as aliphatic and benzylic sp³ C-H bonds. [ABSTRACT FROM AUTHOR]

We have developed a method for auxiliary-directed, palladium-catalyzed β-arylation and alkylation of sp³ and sp² C-H bonds in carboxylic acid derivatives. The method employs a carboxylic acid 2-methylthioaniline- or 8-aminoquinoline amide substrate, aryl or alkyl iodide coupling partner, palladium acetate catalyst, and an inorganic base. By employing 2-methylthioaniline auxiliary, selective monoarylation of primary sp³ C-H bonds can be achieved. If arylation of secondary sp³ C-H bonds is desired, 8-aminoquinoline auxiliary may be used. For alkylation of sp³ and sp² C-H bonds, 8-aminoquinoline auxiliary affords the best results. Some functional group tolerance is observed and amino- and hydroxy-acid derivatives can be functionalized. Preliminary mechanistic studies have been performed. A palladacycle intermediate has been isolated, characterized by X-ray crystallography, and its reactions have been studied. [ABSTRACT FROM AUTHOR]

The article examines the effect of copper salts on the regioselectivity of palladium-catalyzed electron-rich heterocycle arylation. The said effect may arise from the involvement of organocopper intermediates in the reaction and this presumed intermediate can generate without a palladium cocatalyst that will become a cheap and efficient method for heterocycle arylation. Moreover, the best results were obtained by using a combination of lithium t-butoxide base aryl iodide coupling partner.

The palladium-catalyzed direct arylation of indoles, pyrroles, and furans by aryl chlorides has been demonstrated. The method employs a palladium acetate catalyst, 2-(dicyclohexylphosphino)-biphenyl ligand, and an inorganic base. Electron-rich and electron-poor aryl chlorides as well as chloropyridine coupling partners can be used, and arylated heterocycles are obtained in moderate to good yields. Optimization of base, ligand, and solvent is required for achieving best results. [ABSTRACT FROM AUTHOR]

In contrast to traditional diimine-palladium complexes, sterically hindered "sandwich" diimine-palladium adducts act as olefin isomerization catalysts. Terminal olefins are selectively converted to 2-olefins by a sequence of migratory insertion, β-hydride elimination, and olefin displacement. The reaction is performed at 0 °C with 1 mol % of an air-stable precatalyst and tolerates functional groups such as ketones, silyl ethers, and halogens. The isomerization may be used to produce silyl enol ethers from protected allylic alcohols. [ABSTRACT FROM AUTHOR]

Direct arylation and alkylation of amine and carboxylic acid derivatives is achieved with different aryl and alkyl iodides as well as benzyl and allyl bromides in the presence of a palladium catalyst. [ABSTRACT FROM AUTHOR]