Palladium-catalyzed cross-dehydrogenative coupling between anilides and aromatic aldehydes was achieved under aqueous conditions. A wide variety of the desired benzophenone derivatives was isolated in good to excellent yield. The reaction rate acceleration effect of acid and detergent has been demonstrated. Mechanistic insight has been obtained from quantum chemical calculations.Transition metal-catalyzed direct C À H bond functionalization is one of the most important transformations in recent organic synthetic strategies. [1] Although catalytic transformations based on palladium catalysts are the most frequently utilized oxidative coupling methods in organic syntheses, these reactions usually require harsh conditions (high temperature, long reaction time, necessity of inert atmosphere). Therefore the development of efficient palladium-catalyzed oxidative couplings based on highly active catalyst systems under mild reaction conditions is still highly demanded. Regarding the mechanisms of palladium-catalyzed transformations the presence of monometallic palladium complexes in the catalytic cycle is well accepted. [2] However, very recently the special role and activity of bimetallic palladium species has been discovered and demonstrated in several coupling reactions involving a C À H functionalization step. [3] Be-sides the assessment of the synthetic potential of bimetallic complexes in organic chemistry, a thorough understanding of their working mechanism is also essential. [4] There are several applications of palladium-catalyzed oxidative transformations for the formation of new carbon-carbon bonds via functional group-directed ortho-substitution. [5] Very recently, the synthesis of aromatic ketones from phenylpyridines [6] or acetanilides [7] could be achieved by the palladium-catalyzed oxidative coupling of aldehydes [8] including a C À H activation step.The recently described methodologies of Zhou, [7a] Kwong [7b] and Yu [7c] enable the transformation in toluene at 120 8C, 90 8C, and 40 8C, respectively (Scheme 1.). The latter procedure provides the most efficient conditions for the desired coupling due to the relatively short reaction time under the applied conditions (40 8C, 3 h). Utilization of ketocarboxylic acids instead of aldehydes enables the formation of benzophenone derivatives in a similar palladium-catalyzed coupling at room temperature as it was demonstrated by Ge and co-workers. [9] This transformation works efficiently at room temperature and it has excellent functional group tolerance.It is of note, amongst the previous methodologies depicted on Scheme 1., that only Kwongs proce-A C H T U N G T R E N N U N G dure [7b] offers possibilities for the transformation of ortho-substituted acetanilides.Palladium-catalyzed oxidative coupling of acetanilides with aromatic aldehydes results in 2-acylacetanilides and 2-aminobenzophenone derivatives after hydrolytic cleavage of the amide bond, which are impor-

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A novel highly C3 selective metal free trifluoroethylation of indoles using 2,2,2-trifuoroethyl(mesityl)-iodonium triflate was developed. The methodology enables the introduction of a trifluoroethyl group in a fast and efficient reaction under mild conditions with high functional group tolerance. Beyond the synthetic developments, quantum chemical calculations provide a deeper understanding of the transformation.

One of the most widespread synthetic routes to coumarins is the condensation of esters and phenols via the Pechmann reaction. Despite the industrial and technological importance of the reaction, its mechanism is still poorly understood. We have explored several possible reaction paths by DFT calculations at the M05-2X/6-31+G* level. Amphoteric groups and the solvent have a crucial role in the frequent proton-transfer steps of the mechanisms; therefore, we have employed a mixed solvent model, where we combined the implicit PCM model together with an explicit water molecule placed at the actual proton transfer region. The Gibbs free-energy profiles of the possible routes suggest that three parallel channels (featuring water elimination, trans-esterification, and electrophilic attack) operate simultaneously. Enolic routes have prohibitively high activation barriers rendering these paths untenable. The calculated profiles indicate that in each feasible route the first elementary step has the highest activation energy. Reaction intermediates identified on the free-energy profiles can explain several experimental observations.

Free energy surfaces generated via ab initio molecular dynamics simulations for H 2 activation reactions with intramolecular frustrated Lewis pairs (FLPs) point to a concerted (single-step) mechanism of H−H bond cleavage. Statistical analysis carried out for a large number of reaction trajectories reveals notable asynchronicity in the development of donor-H and acceptor-H bonds with the latter being in a more advanced phase. These findings are fully consistent with the results of static quantum chemical calculations demonstrating that the previously established mechanistic picture of FLP-mediated heterolytic H 2 cleavage remains plausible in a finite temperature dynamic model as well. As a consequence of asynchronicity, the excess kinetic energy released upon H 2 cleavage is stored in the form of donor-H bond vibrations, which may influence the mechanism of catalytic hydrogenation.