This paper describes a detailed investigation of factors controlling the dominance of a directing group in Pd-catalyzed ligand-directed arene acetoxylation. Mechanistic studies, involving reaction kinetics, Hammett analysis, kinetic isotope effect experiments, and the kinetic order in various reagents, have been conducted for a series of different substrates. Initial rates studies of substrates bearing different directing groups showed that these transformations are accelerated by the use of electron withdrawing directing groups. However, in contrast, under conditions where two different directing groups are in competition with one another in the same reaction flask, substrates with electron donating directing groups react preferentially. These results are discussed in the context of the proposed mechanism for Pd-catalyzed arene acetoxylation.

This paper describes a new method for the catalytic aerobic oxygenation of unactivated sp3-C–H bonds. This transformation utilizes Pd(OAc)2 as a catalyst in conjunction with NaNO3 as a redox co-catalyst. Both oxime ether and pyridine derivatives are effective directing groups for these reactions. The oxygen incorporated into the product derives from the solvent (acetic acid). Preliminary results show that the addition of simple NaCl to the reaction mixture results in aerobic chlorination under analogous conditions.

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This communication describes a new method for the Pd/polyoxometalate-catalyzed aerobic olefination of unactivated sp3 C–H bonds. Nitrogen heterocycles serve as directing groups, and air is used as the terminal oxidant. The products undergo reversible intramolecular Michael addition, which protects the mono-alkenylated product from over-functionalization. Hydrogenation of the Michael adducts provides access to bicyclic nitrogen-containing scaffolds that are prevalent in alkaloid natural products. Additionally, the cationic Michael adducts undergo facile elimination to release α,β-unsaturated olefins, which can be elaborated in numerous C–C and C–heteroatom bond-forming reactions.

Achieving high selectivity for high volume chemical synthesis is important for lowering energy consumption through reduction in waste. We report the selective synthesis of methyl estersmethyl acetate and methyl butyrate-through catalytic O 2-assisted cross-coupling of methanol with ethanol or 1-butanol using activated, support-free nanoporous gold (npAu). Both wellcontrolled studies on ingots in UHV and experiments under ambient pressure catalytic conditions on both ingots and microspherical hollow shell catalysts reveal guiding principles for controlling selectivity. Under UHV conditions the ester products of the cross-coupling of methanol with both ethanol and 1-butanol evolve near room temperature in temperature programmed reaction studies, indicating that the reactions occur facilely. Under steady-state catalytic operation high, stable activity was observed for cross-coupling in flowing gaseous reactant mixtures at atmospheric pressure and 423 K with negligible combustion. Optimum selectivity for cross

This communication describes detailed investigations of the mechanism of the Pd-catalyzed C-H chlorination and acetoxylation of 2-ortho-tolylpyridine. Under the conditions examined, both reactions proceed via rate limiting cyclopalladation. However, substrate and catalyst order as well as Hammett data indicate that the intimate mechanism of cyclopalladation differs significantly between PdCl2-catalyzed chlorination and Pd(OAc)2-catalyzed acetoxylation.

Here we demonstrate the gas-phase catalytic production of methyl acrylates by oxygen-assisted coupling of methanol with the unsaturated alcohols allyl alcohol and methylallyl alcohol over nanoporous gold (npAu) at atmospheric pressure. Analogous investigations on O-activated Au(110) exhibit the same pattern of reactivity and are used to establish that the competition between methoxy and allyloxy (or methallyloxy) reaction intermediates for adsorption sites, mediated by the reactants themselves, determines the selectivity of reaction. Our results clearly show that the CC bond substantially increases the binding efficacy of the allyloxy (or methallyloxy), thus requiring extremely high methanol mole fractions (>0.99) in order to achieve comparable surface concentrations of methoxy and produce optimum yields of either methacrylate or methyl methacrylate. Allyloxy and methallyloxy were favored by factors of ∼100 and ∼450, respectively, vs methoxy. These values are more than 1 order of magnitude greater than those measured for competitive binding of ethoxy and 1butoxy vs methoxy, demonstrating the strong effect of the carbon−carbon bond unsaturation. The 4.5-fold increase due to the addition of the methyl group in methylallyl alcohol vs allyl alcohol indicates the significant effect of the additional van der Waals interactions between the methyl group and the surface. Gas-phase acidity is also shown to be a good qualitative indicator for the relative binding strength of the alkoxides. This work provides insight into the control of reaction selectivity for coupling reactions and demonstrates the value of fundamental studies on single crystals for establishing key principles governing reaction selectivity. Notably, these oxygen-assisted coupling reactions occur without oxidation of the CC bond.

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