Palladium-catalyzed aerobic homocoupling of aliphatic olefins to dienes: evidence for rate-limiting concerted metalation-deprotonation.

Palladium(ii)-catalyzed dehydrogenative coupling of aliphatic olefins would enable an efficient route to (conjugated) dienes, but remains scarcely investigated. Here, 2-hydroxypyridine (2-OH-pyridine) was found to be an effective ligand for Pd(ii) in the activation of vinylic C(sp)-H bonds. While reoxidation of Pd(0) is challenging in many catalytic oxidations, one can avoid in this reaction that the reoxidation becomes rate-limiting, even under ambient O pressure, by working in coordinating solvents.

Shape-Selective Zeolites for Tandem CO Hydrogenation-Carbonylation Reactions.

The valorization of carbon dioxide as a C1 building block in C-C bond forming reactions is a critical link on the road to carbon-circular chemistry. Activation of this inert molecule through reduction with H to carbon monoxide in the reverse water-gas shift (RWGS) reaction can be followed by a wide spectrum of consecutive carbonylation reactions, but the RWGS is severely equilibrium limited at the moderate temperatures of carbonylations. Here we successfully reconcile both reactions in one pot, while avoiding incompatibilities through a zeolite-based compartmentalized approach.

Oxidative carbonylation of -protected indoles by Rh(III)-zeolites.

The oxidative carbonylation of -protected indoles was investigated to directly synthesize indole-3-carboxylic acids. Using Rh(III)-zeolites as heterogeneous catalysts, the single-site Rh-species reach unprecedented activities (>100 turnovers), while the metal is readily recovered after reaction. X-ray absorption spectroscopy (XAS) provided evidence for site-isolation of Rh(III) species on the zeolite.

Cu-α-diimine Compounds Encapsulated in Porous Materials as Catalysts for Electrophilic Amination of Aromatic C-H Bonds.

Electrophilic amination has emerged as a more environmentally benign approach to construct arene C-N bonds. However, heterogeneous catalysts remain largely unexplored in this area, even though their use could facilitate product purification and catalyst recovery. Here we investigate strategies to heterogenize a Cu(2,2'-bipyridine) catalyst for the amination of arenes lacking a directing group with hydroxylamine--sulfonic acid (HOSA).