A heterogeneous reusable palladium(II)-bis(N-heterocyclic carbene) catalyst was prepared and shown to catalyze the intramolecular C(sp 3 )À H activation/cyclization of N-alkyl-2-bromoanilines furnishing indolines. This new catalytic system was based on a bis-imidazolium ligand immobilized on a spaced crosslinked polystyrene support. The iodide ligands on the catalyst played a central role in the efficiency of the process occurring through a "release and catch" mechanism. The heterogeneous nature of the catalyst was further exploited in the design of a continuous-flow protocol that allowed a more efficient recovery and reuse of the catalyst, as well as a very fast and safe procedure.

Herein, we report the development of an effective synthetic protocol for the synthesis of oxindoles in flow based on a C(sp 3 )−H activation process promoted by a supported Nheterocyclic carbene palladium heterogeneous catalytic system using cyclopentyl methyl ether (CPME) as the reaction medium. The design of the catalyst, the selection of the solvent medium, and the definition of a tailored continuous flow reactor have been all designed to establish an efficient waste-minimized process for the intramolecular cyclization of N-methyl-2-halo-acetanilides. The use of CPME in its aqueous azeotropic mixture has allowed us to reach high yields of products with a simplified precipitation workup that includes the downstream process separation and recycling of the solvent. An assessment of the environmental and safety hazard features has also been made in order to better clarify the implications in terms of sustainability of the newly developed process.

No abstract

We herein report a general and efficient enantioselective C–H arylation of aryl bromides based on the use of BozPhos as the bisphosphine ligand and SP‐NHC‐PdII as recoverable heterogeneous catalyst. By exploiting the “release and catch” mechanism of action of the catalytic system, we used BozPhos as a broadly applicable chiral ligand, furnishing high enantioselectivities across all types of examined substrates containing methyl, cyclopropyl and aryl C–H bonds. For each reaction, the reaction scope was investigated, giving rise to 30 enantioenriched products, obtained with high yields and enantioselectivities, and minimal palladium leaching. The developed catalytic system provides a more sustainable solution compared to homogeneous systems for the synthesis of high added‐value chiral products through recycling of the precious metal.

No abstract