Scheme 3. Electrophilic Functionalization Pathway (Mechanism ii): One-Electron Oxidation of Palladacycle A Scheme 4. Electrophilic Functionalization Pathway (Mechanism iii): Two-Electron Oxidation of Palladacycle A Scheme 5. Pd(OAc) 2 -Catalyzed sp 2 C-H Acetoxylation with PhI(OAc) 2 8-10 Scheme 6. Pd(OAc) 2 -Catalyzed sp 3 C-H Acetoxylation with PhI(OAc) 2 8,10,14

As oil supplies dwindle, there is a growing need to develop new routes to chemical intermediates that utilize alternative feedstocks. We report here a synthesis of para-xylene, one of the highest volume chemicals derived from petroleum, using only ethylene as a feedstock. Ethylene is an attractive alternative feedstock, as it can be derived from renewable biomass resources or harnessed from large domestic shale gas deposits. The synthesis relies on the conversion of hexene (from trimerization of ethylene) to 2,4-hexadiene followed by a Diels-Alder reaction with ethylene to form 3,6-dimethylcyclohexene. This monoene is readily dehydrogenated to para-xylene uncontaminated by the ortho and meta isomers. We report here a selective synthesis of para-xylene, uncontaminated by the ortho or meta isomers, using ethylene as the sole feedstock.

This report describes a new Pd-catalyzed oxidation reaction for the stereospecific conversion of enynes into cyclopropyl ketones. Unlike related PdII/0, Au, and Pt-catalyzed cyclopropane-forming reactions, these transformations proceed with net inversion of geometry with respect to the starting olefin. This result is consistent with a PdII/IV mechanism in which the key cyclopropane-forming step involves nucleophilic attack of a tethered olefin onto the PdIV−C bond.

This paper presents a detailed investigation of the factors controlling site selectivity in the Pd-mediated oxidative coupling of 1,3-disubstituted and 1,2,3-trisubstituted arenes (aryl-H) with cyclometalating substrates (L~C-H). The influence of both the concentration and the steric/electronic properties of the quinone promoter are studied in detail. In addition, the effect of steric/electronic modulation of the carboxylate ligand is discussed. Finally, we demonstrate that substitution of the carboxylate for a carbonate X-type ligand leads to a complete reversal in site selectivity for many arene substrates. The origins of these trends in site selectivity are discussed in the context of the mechanism of Pd-catalyzed oxidative cross-coupling.

The highly thermally stable anthraphos-based iridium pincer complex ( iPr4 Anthraphos)Ir(C 2 H 4 ) 3, was shown to catalyze transfer dehydrogenation of pentene and pentane using various olefins as acceptors in the temperature range of 160−250 °C. Using pentene itself as an acceptor, disproportionation of pentene to pentane and pentadiene was observed, but yields of (E)-and (Z)-1,3-pentadienes (piperylenes) were limited to ∼25% as a result of a self-Diels−Alder reaction of the 1,3dienes to produce isomeric mixtures of the C 10 dimers. Using propylene as the acceptor, higher yields of piperylenes were obtained (∼40%), but self-Diels−Alder adducts were again observed along with low fractions of propylene/pentadiene Diels− Alder adducts. Using ethylene as the acceptor, the pentadienes produced via hydrogen transfer undergo an in situ Diels−Alder reaction with ethylene to produce 3-methylcyclohexene (along with toluene from further dehydrogenation) in good yields (65%). 3-Methylcylohexene was quantitatively dehydrogenated to toluene over a heterogeneous Pd/C catalyst.