Pd-Catalyst Containing a Hemilabile P,C-Hybrid Ligand in Amino Dicarbonylation of Aryl Halides for Synthesis of α-Ketoamides

The amino dicarbonylation of aryl halides affording a-ketoamides with Pd catalysts is highly dependent on the stereoelectronic properties of the involved ligands. Ionic diphosphine ligand L4 can serve as precursor of a hemilabile P,C (phosphine, carbene)-hybrid ligand to form a stable Pd(II)-complex, Pd-L4. In contrast, analogues L1-L3 with a similar 1-(thiophen-3-yl)-benzimidazolyl skeleton behave as typical (mono/di)phosphines. The catalytic system resulting from the complexation of PdCl2 (MeCN)(2) and L4 exhibits good catalytic performance in terms of aryl iodides conversion (81-95%) and alpha-ketoamide selectivity (80-91%), as well as the available recyclability in the RTIL of [Bpy]BF4. The in situ FT-IR analysis reveals that the PdCl2 (MeCN)(2)-L4 catalytic system favors the amino dicarbonylation toward alpha-ketoamides according to the proposed mechanism of cycle I, which involves two independent CO-insertion steps.

Automated summary

The study investigates the mechanism of Pd-catalyzed amino dicarbonylation of aryl halides using different ligands, with the ionic diphosphine ligand L4 showing superior catalytic performance for achieving high conversion rates and selectivity.