A new palladium mediated "one pot" synthesis of thioamides from aromatic carboxylic acids (ArCOH + RNCS → ArC(S)NHR + CO) was discovered by gas-phase experiments and theoretical studies. Palladium-mediated decarboxylation of aromatic carboxylic acids followed by addition of substituted isothiocyanates leads to the corresponding thioamide derivatives.

Gas-phase reactivity of the copper hydride anions [CuH] and [CuH] toward a range of neutral reagents has been examined via multistage mass spectrometry experiments in a linear ion trap mass spectrometer in conjunction with isotope labeling studies and Density Functional Theory (DFT) calculations. [CuH] is more reactive than [CuH], consistent with DFT calculations, which show it has a higher energy HOMO. Experimentally, [CuH] was found to react with CS via hydride transfer to give thioformate (HCS) in competition with the formation of the organometallic [CuCS] ion via liberation of hydrogen; CO via insertion to produce [HCuOCH]; methyl iodide and allyl iodide to give I and [CuHI]; and 2,2,2-trifluoroethanol and 1-butanethiol via protonation to give hydrogen and the product anions [CuH(OCHCF)] and [CuH(SBu)]. In contrast, the weaker acid methanol was found to be unreactive. DFT calculations reveal that the differences in reactivity between CS and CO are due to the lower lying π* orbital of the former, which allows it to accept electron density from the Cu center to form the initial three-membered ring complex intermediate, [HCu(η-CS)]. In contrast, CO undergoes the barrierless side-on hydride transfer promoted by the high electronegativity of the oxygen atoms. Side-on S2 mechanisms for reactions of [CuH] with methyl iodide and allyl iodide are favored on the basis of DFT calculations. Finally, the DFT calculated barriers for protonation of [CuH] by methanol, 2,2,2-trifluoroethanol, and 1-butanethiol correlate with their gas-phase acidities, suggesting that reactivity is mainly controlled by the acidity of the substrate.

Gold-catalyzed domino processes constitute a useful alternative to C-H functionalization for the synthesis of functionalized (hetero)arenes. Herein, we report computational studies on the gold-catalyzed cyclization alkynylation of keto-allenes with ethynylbenziodoxole (EBX) reagents, which identified a gold(i) picolinate complex as the active catalyst, giving the first mechanistic insights into this transformation.

Density functional theory (DFT) was used to study the reaction mechanism of cyanomethylation of aldehydes catalyzed by nickel pincer complexes under base-free conditions. The C-bound cyanomethyl complex, which was initially thought to be the active catalyst, is actually a precatalyst, and in order for the catalytic reaction to commence, it has to convert to the less-stable N-bound isomer. The carbon–carbon bond formation then proceeds via direct coupling of the N-bound isomer and the aldehyde to give a zwitterionic intermediate with a pendant alkoxide function, which is further stabilized by hydrogen-bonding interaction with water molecules (or alcohol product). The N-bound alkoxide group of the zwitterionic intermediate is subsequently substituted by MeCN via an associative mechanism, followed by deprotonation of the coordinated MeCN to afford the final product. It was found that the transition structure for the exchange reaction (substitution of MeCN for the alkoxide group) is the highest energy point on the catalytic cycle, and its energy crucially influences the catalyst efficiency. The Ni complexes ligated by bulky and weak trans-influencing pincer ligands are not appropriate catalysts for the cyanomethylation reaction due to the involvement of very-high-energy transition structures for the exchange reaction. In contrast, benzaldehydes with electron-withdrawing substituents are capable of stabilizing the exchange reaction transition structure due to the increased stability of the zwitterionic intermediate, leading to acceleration of the catalytic reaction.