Catalytic carbonylation of quaternary ammonium salts under anhydrous conditions was investigated using palladium catalyst. The carbonylation of tetramethylammonium iodide was chosen as a model reaction and studied systematically. Ligand-free PdCl₂ showed efficient catalytic performance for this transformation. A palladium catalyst loading as low as 0.05 mol% was sufficient for high yield (96.9%) of N,N-dimethylacetamide, corresponding to a turnover frequency of 242 h⁻¹. Under optimum conditions, several other quaternary ammonium halides were also carbonylated to corresponding tertiary amides in moderate to excellent yields. The catalytic activity of commercial palladium on activated carbon (Pd/C) catalyst was also evaluated. The Pd/C catalyst exhibited high activity for this carbonylation reaction and could be recycled six times with a slight decrease in activity. Furthermore, mechanistic considerations concerning Pd-catalyzed carbonylation of quaternary ammonium halides were also discussed. Copyright © 2014 John Wiley & Sons, Ltd.

This work describes a highly efficient unstrained C(sp³)―N bond activation approach for synthesis of N,N-dimethylacetamide (DMAc) via catalytic carbonylation of trimethylamine using a PdCl₂/bipy (bipy = 2,2′-bipyridine)/Me₄NI catalyst system. A low Pd catalyst dosage (1.0 mol%) is sufficient for high selectivity (98.1%) and yield (90.8%), with a turnover number (TON) of 90.0 mmol of DMAc obtained per mmol of PdCl₂ employed under mild reaction conditions. The influence of reaction parameters such as catalyst precursor dosage, ligand type and promoter on activity is investigated. This work also discusses in detail the halide promoter's role in the reaction, and provides a plausible mechanism based on the intermediates methyl iodide and acetyl iodide. Analyses indicate that the carbonylation of trimethylamine may proceed through an active intermediate acetyl iodide formed by carbonylation of methyl iodide generated from the decomposition of the promoter Me₄NI under reaction conditions. The formation of acetyl iodide favors the cleaving efficiency of the inert unstrained C(sp³)―N bond of trimethylamine. Copyright © 2013 John Wiley & Sons, Ltd.

We report an efficient process for the synthesis of diethyl malonate (DEM) and other malonates through the palladium-catalyzed carbonylation of chloroacetates. Excellent selectivity (96 %) and yield (94 %) were obtained without the formation of Pd black. For the first time, a weakly alkaline buffer was used to control the selectivity for DEM in the reaction and we discuss the relationship between the buffer medium and selectivity in the reaction. The combination of anisole as the solvent and a Na₂HPO₄/NaH₂PO₄ buffer was beneficial for completely restraining the phase-transfer-catalyzed substitution of DEM with ethyl chloroacetate, as well as accommodating the proposed [(PPh₃)₂PdI]⁻[Bu₄N]⁺ intermediate, by providing a suitable environment for its stable existence. We achieved the highest efficiency in the catalytic cycle by fine-tuning the balance between the rates of oxidative addition and reductive elimination; moreover, we synthesized a recoverable heterogeneous polymer-bound Pd catalyst in 85 % yield that could be reused without an appreciable loss in activity over four cycles.

The catalytic properties of CuX_n/N-ligands (X = Cl, Br and I; n = 1 or 2) in oxidative carbonylation of methanol were investigated. It was found that the interaction of halogen anions, N-ligands and Cu (I) affected the catalytic performance of copper complex catalyst in the reaction, especially iodide anion and 1,10-phenanthroline (Phen). When CuI/Phen was used as a catalyst, the conversion of methanol was 42.6%, the selectivity to dimethyl carbonate was 99.2% and the TOF was 13.1 h⁻¹ at an optimized conditions: CuI/Phen 0.2 mol l⁻¹, 120 °C, 2 h, 2.4 MPa, P_CO/P_O2 = 2:1. Compared with the plain CuI catalyst, the catalytic activity of CuI/Phen increased about 36 times. When CuI/Phen catalyst was immobilized on polystyrene (PS), the heterogenized catalyst, CuI/Phen–NH–PS, also exhibited very high catalytic activity in oxidative carbonylation. The CuI/Phen—NH—PS catalyst remained its high catalytic activity even after seven recycles. The average weight loss of CuI/Phen—NH—PS after reaction was less than 1.0%, and the leaching of copper was only about 0.15% in each recycling test. Copyright © 2010 John Wiley & Sons, Ltd.

Titania-silica immobilized Co(salen) complexes containing the heterobinuclear site were prepared by the sol–gel method for the catalytic synthesis of methyl N-phenylcarbamate (MPC) by the oxidative carbonylation of aniline. It was found that the Ti:Si mole ratio had an important effect on the catalytic performance of Co(salen) complexes. When the Ti:Si ratio was 0.1, titania-silica supported Co(salophen) showed the best catalytic activity. Under the reaction conditions, Co(salophen)/TS-0.1, 0.5 g, aniline 11 mmol, methanol 25 ml, KI 2.2 mmol, CO:O₂ 9:1, total pressure 6 MPa, 150 °C, 3 h, the conversion of aniline and the selectivity of MPC were 60.7 and 88.1%, respectively. The XRD studies showed that titania was highly dispersed in the silica matrix. Co(salophen)/TS-0.1 was reused five times with no significant loss of the activity, and no Co leaching was observed in the reaction. Copyright © 2009 John Wiley & Sons, Ltd.