Palladium-catalyzed 1,1-aryloxygenation of terminal olefins

This paper describes the 1,1-arylacetoxylation of diverse α-olefins using organostannanes and hypervalent iodine oxidants. The reaction provides a convergent approach for generating a C-C and a C-O bond as well as a new stereocenter in a single catalytic transformation.     

Palladium-catalyzed isomerization of methylenecyclopropanes in acetic acid

[reaction: see text] Pd(PPh3)4-catalyzed isomerization of MCPs 1 in acetic acid proceeds smoothly at 80 degrees C in toluene to give the corresponding 1-substituted or 1,1-disubstituted dienes 2 in good to excellent yields under mild conditions. The plausible mechanism has been disclosed on the basis of a deuterium-labeling experiment.     

Palladium-catalyzed reactions of vinylidenecyclopropanes with acetic acid

Pd(PPh₃)₄-catalyzed reactions of vinylidenecyclopropanes 1 with acetic acid proceeded smoothly at 80 °C in toluene to give the corresponding acetylated dienes 2 in moderate to good yields in the presence of DPEphos ligand. The plausible mechanism is proposed on the basis of the control and deuterium labeling experiments.     

Microwave-promoted and chelation-controlled double arylations of terminal olefinic carbon of vinyl ethers

Herein we report a rapid, palladium-catalyzed terminal diarylation of the chelating olefin N,N-dimethyl(2-ethenyloxy)ethanamine under noninert conditions utilizing controlled microwave heating as a convenient energy source. Among the aryl bromides examined, both electron-rich and electron-poor substrates were demonstrated to furnish useful yields after only 10-120 min of directed microwave heating at 160-200 degrees C. The good terminal regioselectivity suggests that the precatalyst (Herrmann's palladacycle) serves as a source of weakly coordinated palladium(0) in the investigated high-temperature Heck process.     

Palladium-catalyzed aerobic oxidation of terminal olefins with electron-withdrawing groups in scCO2

Product control of palladium-catalyzed aerobic oxidation of terminal olefins with electron-withdrawing groups can be achieved through modifying reaction conditions. When the oxidant, such as CuCl₂/O₂, benzoquinone/O₂ or O₂, was present in scCO₂, aerobic oxidation of terminal olefins goes smoothly. With enough MeOH and sufficient oxygen, acetalization preponderated over cyclotrimerization, while with little MeOH as co-solvent in scCO₂ or no MeOH in DMF and an appropriate pressure of O₂, cyclotrimerization of terminal olefins became the dominated reaction. When oxygen is absent and triethylamine was added into the reaction system, palladium-catalyzed C-N bond formation occurs to produce β-amino acid derivatives as the sole product.     

An investigation of the equilibria formed between palladium(II) chloride complexes and terminal olefins in acetic acid solution

An investigation of the equilibria formed between the terminal olefins 1-hexene and 1-octene and Na₂Pd₂Cl₆ in glacial acetic acid, using preparative, Raman, and ultra-violet and visible spectroscopic methods has shown that the principal olefin complexes formed are Na[Pd₂Cl₅(Olefin)], at low olefin concentrations, and [Pd₂Cl₄(Olefin)₂], at high olefin concentrations. The value is emphasised of using the Method of Continuous Variations (Job's Method) at as wide a range of wavelengths as possible for studying systems in which more than one metal—ligand complex is formed.     

Palladium-catalyzed reduction of olefins with triethylsilane

The versatility of the palladium(II) chloride and triethylsilane system has been tested in the hydrogenation of 1-alkenes. The reduction of 1-alkenes was carried out in the presence of triethylsilane, ethanol and a catalytic amount of palladium(II) chloride, at room temperature. This facile and efficient method affords high yields for hydrogenation of unsaturated alkenes to the corresponding alkanes.     

Palladium-catalyzed intramolecular oxidative alkylation of unactivated olefins

Reaction of 5,5-dimethyl-8-nonene-2,4-dione catalyzed by PdCl2(CH3CN)2 (5 mol %) in the presence of CuCl2 (2.5 equiv) at room temperature for 3 h formed 2-acetyl-3,6,6-trimethyl-2-cyclohexenone in 96% isolated yield. Palladium-catalyzed intramolecular oxidative alkylation tolerated a range of substitution and was applicable to the synthesis of spirobicyclic compounds and to the cyclization of zeta-alkenyl beta-keto esters.     

Palladium-catalyzed addition reaction of polyhaloalkanes to olefins

Pd(OAc)₂ combined with phosphines catalyzes homolytic cleavage of the C—Cl bond of CCl₄ and CCl₃CO₂CH₃ leading to facile addition to olefins under mild conditions. BrCCl₃ also reacts with olefins to give 1,1,1-trichloro-3-bromoalkanes. The reaction is accelerated under CO atmosphere, and the presence of bases such as NaOAc or K₂CO₃ is essential to attain high yields of the adducts.     

Palladium-catalyzed phosphinylthiolation of terminal alkynes

Phosphinylthiolation of terminal alkynes with Ph₂P(O)SBu or a related compound proceeds in the presence of a palladium–PEt₃ catalyst system. Activity and stereoselectivity are highly dependent on the nature of solvent, ethylbenzene, and n-hexanol (or t-amyl alcohol) being E- and Z-selective, respectively.     

Dioxygen-promoted regioselective oxidative heck arylations of electron-rich olefins with arylboronic acids

Arylations of electron-rich heteroatom-substituted olefins were performed with arylboronic acids. This appears to constitute the first example of palladium(II)-catalyzed internal Heck arylations. The novel protocol exploits oxygen gas for environmentally benign reoxidation and a stable 1,10-phenanthroline bidentate ligand to promote the palladium(II) regeneration and to control the regioselectivity. Internal arylation is strongly favored with electron-rich arylboronic acids. DFT calculations support a charge-driven selectivity rationale, where phenyls substituted with electron-donating groups prefer the electron-poor alpha-carbon of the olefin. Experiments, verified by calculations, confirm the cationic nature of the catalytic route. This Heck methodology provides a facile and mild access to functionalized enamides. Controlled microwave heating and increased oxygen pressure were used to further reduce the reaction time to 1 h.     

Palladium-catalyzed cyclopropanation of electron-deficient olefins with aryldiazocarbonyl compounds

A concise and efficient protocol for the preparation of cyclopropanes from various aryldiazocarbonyl compounds and electron-deficient olefins catalyzed by Pd(OAc)₂ is reported.     

Palladium-catalyzed reaction of bromine- and iodine-containing isothiazoles with olefins

3-Bromo-4-alkenylisothiazoles were synthesized by the reaction of 3-bromo-4-iodoisothiazole with olefins in the presence of palladium acetate Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 534–536, March, 1998.     

Ligand and pH influence on manganese-mediated peracetic acid epoxidation of terminal olefins

[reaction: see text] Nineteen Mn(II) complexes were screened for the catalytic epoxidation of terminal olefins using peracetic acid. Few of these complexes are efficient catalysts at pH < 2, but many are effective at 1 mol % catalyst loading at pH 4. With 0.1 mol % loading, four complexes epoxidize 1-octene in approximately 80% yield in 5 min. The relative reactivity of the catalysts toward different olefins was probed using a multicomponent intermolecular competition reaction.     

Palladium-catalyzed Heck-type reaction of 2-chloro acetamides with olefins

Conditions have been developed for the palladium-catalyzed Heck-type reaction of 2-chloro acetamides with several olefins. The regiochemistry of the products obtained speaks in favor of an involvement of palladium enolates in this reaction.     

Palladium-catalyzed intramolecular hydroalkylation of unactivated olefins with dialkyl ketones

[reaction: see text] Treatment of 3-butenyl heptyl ketone with substoichiometric amounts of PdCl(2)(CH(3)CN)(2) (10 mol %), HCl (0.1 equiv), and CuCl(2) (0.3 equiv) in dioxane at 70 degrees C for 12 h in a sealed tube formed 2-hexylcyclohexanone in 77% isolated yield. A number of alkyl 3-butenyl ketones underwent hydroalkylation under these conditions to form 2-substituted cyclohexanones in moderate to good yield.     

Palladium-catalyzed heck arylations of allyl alcohols in ionic liquids: remarkable base effect on the selectivity

Pd-catalyzed Heck arylation of allyl alcohols in tetraalkylammonium ionic liquids (ILs) can be made highly selective toward the formation of either aromatic carbonyl compounds or aromatic conjugated alcohols by carefully choosing both the IL and the base.     

Palladium-catalyzed aminoallylation of activated olefins with allylic halides and phthalimide

The three-component aminoallylation reaction of the activated olefins 2 with the phthalimide 1a and allyl chloride proceeded very smoothly in the presence of Pd(2)dba(3).CHCl(3) (5 mol %)/P(4-FC(6)H(4))(3) (40 mol %) and Cs(2)CO(3) (3 equiv against 2) in dichloromethane at room temperature to give the corresponding aminoallylated products, N-pent-4-enylphthalimides 3, in 58-99% yields. The reaction of oxazolidinone 1b also proceeded very smoothly to give N-(2,2-dicyano-1-phenylpent-4-enyl)oxazolidinone in a quantitative yield; however, the Tsuji-Trost-type allylation products 4 were obtained in the case of dibenzylamine, N-tosylaniline, and pyrrolidin-2-one. Further, 2 underwent cycloaddition with N-tosylvinylaziridine 9a in the presence of Pd(2)dba(3).CHCl(3) (5 mol %)/P(4-FC(6)H(4))(3) (40 mol %) in THF at room temperature, giving the corresponding pyrrolidines 11 in 69-99% yields.