The palladium-catalyzed oxidation of alkyl enol ethers to enals, which employs low loadings of a palladium catalyst, is described. The mild oxidation conditions tolerate a diverse array of functional groups, while allowing the formation of di-, tri-, and tetrasubtituted olefins. The application of this methodology to intramolecular reactions of alkyl enol ethers containing pendant alcohols provides furan and 2,5-dihydrofuran products.

Regio- and stereoselective alkane dehydrogenation is a difficult challenge in organometallic chemistry. Intermolecular reactions of this type typically produce numerous olefin stereo- and regioisomers. Herein, we report our initial investigations into the intramolecular dehydrogenation of a datively bound alkyl ligand, demonstrating the first example of a site-selective dehydrogenation of an unactivated acyclic alkyl group. The alkyl group is located on an acylphosphine ligand that is coordinated to a Cp*IrCl2 monomer. A mechanistic proposal, guided by the isolation of a dimeric iridium complex and supported by computational results, is also described.

The allylic oxidation of cis-vinylsilanes is reported. The reaction requires a low catalyst loading of Pd(OAc)2 without the need for an external ligand. Interestingly, trans-vinylsilanes are unreactive, whereas allylic oxidations of cis-vinylsilanes proceed in good yields giving a single diastereo- and regioisomer of the branched allylic acetate trans-vinylsilane when benzoquinone is employed. The use of PhI(OAc)2 as oxidant in place of benzoquinone provides the branched, cis-vinylsilane as the major product. Additionally, the first intramolecular allylic C–H etherifications of cis-vinylsilanes to give oxygen heterocycles are also described.

The synthesis of unsymmetrical diaryl ketonesvia the Fukuyama coupling of thioesters and organozinc reagents is described. Typically, the synthesis of diaryl ketones using this methodology provides low yields. The simple complex, Pd(dba)2, was found to convert a variety of aryl thioesters to diaryl ketones in good yields.

Palladium acetate and tri-tert-butylphosphine react at room temperature via C–H activation of a tert-butyl group to form the novel palladium(II) complex [(PtBu3)Pd(CH2C(CH3)2PtBu2)(OAc)]. This cyclometalated complex can be reduced to Pd(PtBu3)2 by either heat or hydrogen, but is resistant to reduction by alkoxide bases and amines. As a result of the existence of this cyclometalated complex, the production of catalytically active palladium(0) species generated in situ from Pd(OAc)2 and tri-tert-butylphosphine is diminished, as evident by the catalytic inactivity of this complex. Additionally, datively bound tri-tert-butylphosphine is easily displaced by amines and less basic phosphines to form a series of novel cyclometalated palladium(II) complexes.

The synthesis of an iridium complex bearing the unusual di-tert-butylheptanoylphosphine ligand is described. In exploring the chemistry of this complex, it was found that the acylphosphine ligand underwent facile transmetalation to silver in the presence of silver triflate. The result was the formation of a novel anionic iridium complex. The X-ray crystal structure revealed that the anion [Cp*Ir(OTf)3]− acts as a chelating ligand for silver. The reactivity of this complex in the presence of small molecules is also described.

A variety of N-aryl-1H-indazoles and benzimidazoles were synthesized from common arylamino oximes in good to excellent yields. The product selectivity depends upon the base used in the reaction, as triethylamine promoted the formation of benzimidazoles, whereas 2-aminopyridine promoted the formation of N-arylindazoles. This method is valuable to the synthetic community because both indazoles and benzimidazoles are prevalent in pharmaceuticals.

A palladium catalyst that converts terminal olefins to linear allylic acetates at lower catalyst loadings and faster reaction times than current systems is reported. This reaction can be conducted using benzoquinone as the oxidizing agent or catalytic amounts of copper and hydroquinone under one atmosphere of oxygen. Preliminary reactivity studies of π-allylpalladium complexes under our reaction conditions do not provide results similar to those obtained in the catalytic reaction, which may suggest an alternative reaction pathway. The palladium catalyst is ligated by an aryloxyalkyl aryl sulfide, which is identified as a new ligand for homogeneous catalysis.

A catalytic amount of zinc chloride in combination with a palladium catalyst ligated by a monodentate phosphine allows the coupling of aryl and alkyl thiols with aryl bromides in high yields. The addition of zinc chloride to a palladium catalyst system that reportedly failed to promote sulfide formation allows this once ineffective catalyst system to provide the sulfide product in good yield. This paper describes a high-yielding and general monodentate phosphine-ligated palladium catalyst for biaryl and alkyl aryl sulfide formation.

The synthesis of unsymmetrical diaryl ketonesvia the Fukuyama coupling of thioesters and organozinc reagents is described. Typically, the synthesis of diaryl ketones using this methodology provides low yields. The simple complex, Pd(dba)2, was found to convert a variety of aryl thioesters to diaryl ketones in good yields.