Catalytic Enantioselective Aminopalladation-Heck Cascade.

Domino processes initiated by intramolecular nucleopalladation of alkynes have been developed into powerful synthetic tools for the synthesis of functionalized heterocycles. However, a catalytic enantioselective version of this class of reactions remains scarce. We report herein that reaction of 2-alkynylanilines with prochiral cyclopentenes in the presence of a catalytic amount of Pd(OAc)2 , a chiral bidentate pyrox ligand and O2 as terminal oxidant affords the structurally diverse indole-cyclopentene conjugates bearing two stereocenters in a highly diastereo- and enantio-selective manner. One of the products is converted to a heavily functionalized tetracyclic indolinone derivative.

Auto-Tandem Catalysis: PdII -Catalysed Dehydrogenation/Oxidative Heck Reaction of Cyclopentane-1,3-diones.

A PdII catalyst system has been used to successfully catalyse two mechanistically distinct reactions in a one-pot procedure: dehydrogenation of 2,2-disubstituted cyclopentane-1,3-diones and the subsequent oxidative Heck coupling. This auto-tandem catalytic reaction is applicable to both batch and continuous flow processes, with the latter being the first example of a tandem aerobic dehydrogenation/oxidative Heck in flow. In addition, a telescoped reaction involving enantioselective desymmetrisation of the all-C quaternary centre was successfully achieved.

Product Control using Substrate Design: Ruthenium-Catalysed Oxidative C-H Olefinations of Cyclic Weinreb Amides.

A new class of Weinreb amides has been developed as directing groups for the ruthenium-catalysed regioselective oxidative C-H olefination. The new Weinreb amides successfully inhibit the N-O bond reductive cleavage usually associated with the cationic ruthenium system, thereby keeping intact the synthetic utility of Weinreb amides. Mechanistic studies reveal interesting aspects of the directing group capabilities of Weinreb amides when compared to simple amides of similar structures.

A facile and rapid access to resveratrol derivatives and their radioprotective activity.

A facile and rapid access to resveratrol derivatives has been achieved based on palladium-catalyzed oxidative Heck reaction of aryl boronic acids with styrenes followed by demethylation in moderate to good yields. A series of resveratrol derivatives with various functional groups has been synthesized easily. The radioprotective activity of synthesized compounds has also been evaluated using rat thymocytes. The results revealed that some resveratrol derivatives efficiently protected the thymocytes from radiation-induced apoptosis.

Mechanochemical Rhodium(III)-Catalyzed C-H Bond Functionalization of Acetanilides under Solventless Conditions in a Ball Mill.

In a proof-of-principle study, a planetary ball mill was applied to rhodium(III)-catalyzed C-H bond functionalization. Under solventless conditions and in the presence of a minute amount of Cu(OAc)2, the mechanochemical activation led to the formation of an active rhodium species, thus enabling an oxidative Heck-type cross-coupling reaction with dioxygen as the terminal oxidant. The absence of an organic solvent, the avoidance of a high reaction temperature, the possibility of minimizing the amount of the metallic mediator, and the simplicity of the protocol result in a powerful and environmentally benign alternative to the common solution-based standard protocol.

Combining rhodium and photoredox catalysis for C-H functionalizations of arenes: oxidative Heck reactions with visible light.

Direct, oxidative metal-catalyzed C-H functionalizations of arenes are important in synthetic organic chemistry. Often, (over-)stoichoimetric amounts of organic or inorganic oxidants have to be used in these reactions. The combination of rhodium and photoredox catalysis with visible light allows the direct C-H olefination of arenes. Small amounts (1 mol%) of a photoredox catalyst resulted in the efficient C-H functionalization of a broad range of substrates under mild conditions.

Scalable synthesis of oxazolones from propargylic alcohols through multistep palladium(II) catalysis: ß-selective oxidative Heck coupling of cyclic sulfonyl enamides and aryl boroxines.

A whale of a scale: The title oxidative Heck coupling proceeded with unusual ß selectivity to generate a variety of branched substituted oxazolones (see scheme; Ts=p-toluenesulfonyl). The three-step synthesis from readily available starting materials with a simple palladium catalyst and inexpensive reagents could be carried out in a single reaction vessel or scaled up for the preparation of large amounts of these amino acid precursors.

Heterogeneous Single-Site Catalysts for C-H Activation Reactions: Pd(II)-Loaded S,O-Functionalized Metal Oxide-Bisphosphonates.

Heterogeneous single-site catalysts contain spatially isolated, well-defined active sites. This allows not only their easy recovery by solid-liquid separation but also the detailed active site design similar to homogeneous catalysts. Here, heterogeneous Pd(II) single-site catalysts were assembled, based on mesoporous metal oxide-bisphosphonate materials as supports. This new family of hybrid organic-inorganic materials with tunable porosity was further functionalized with thioether ligands containing S,O-binding sites that enhance the activity of Pd(II) for C-H activation reactions. The structures of the resulting Pd(II) single-site catalysts were carefully analyzed via solid-state NMR spectroscopy, via texture analysis by N2 physisorption, infrared spectroscopy, and transmission electron microscopy. Furthermore, the immediate environment of the isolated Pd(II) active sites was studied with X-ray absorption spectroscopy. A clear relationship between the thioether ligand surface density and catalyst activity could be established. Significantly higher yields were obtained using highly porous metal oxide-bisphosphonate materials as supports compared to materials with lower porosities, such as conventional metal oxides, indicating that the high surface area facilitates the presence of isolated, well-accessible S,O-supported Pd(II) active sites. A wide scope of model substrates, including industrially relevant arenes, can be converted with high yields by the optimal heterogeneous Pd catalyst.

Fujiwara-Moritani Reaction of Weinreb Amides using a Ruthenium-Catalyzed C-H Functionalization Reaction.

The ruthenium-catalyzed Fujiwara-Moritani reaction (oxidative-Heck reaction) of Weinreb amides is reported herein. The reaction affords exclusively ortho-C-H olefination products, has excellent substrate scope and tolerates halogen functionalities, which increase the synthetic utility of the method. A variety of activated olefins as well as styrenes can be employed as coupling partners.