95724-98-4

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• 201230-82-2 carbon monoxide 
• 623-00-7 4-bromobenzenecarbonitrile 
• 109-89-7 diethylamine 
• 3058-39-7 4-iodobenzonitrile 

Relevant academic research and scientific papers

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 α-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 α-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 α-ketoamides according to the proposed mechanism of cycle I, which involves two independent CO-insertion steps.

Palladium-Catalysed Double Carbonylation of Aryl Halides To Give α-Keto Amides. Mechanistic Studies

Various aryl halides are catalytically converted into α-keto amides and amides on treatment with secondary amines and carbon monoxide.Palladium complexes containing tertiary phosphine ligands, particularly diphenylmethylphosphine and 1,4-bis(diphenylphosphino)butane, are most effective among other transition-metal complexes.Detailed examination of factors controlling the reaction rates and selectivity for α-keto amide formation revealed the following characteristics of the reactions. (a) Reactivity of phenyl halide decreases in the order PhI > PhBr >> PhCl. (b) Oxidative addition of phenyl bromide constitutes the rate-determining step in double carbonylation of phenyl bromide, whereas in the reaction of phenyl iodide the rate determinig step is associated with the reaction of a catalitically active palladium species with carbon monoxide. (c) Introduction of an electron-withdrawing substituent into the para position of phenyl halide enhances the reactivity but decreases the selectivity for α-keto amide. (d) Employment of amines of high basicity (pKb Et2NH > piperidine > hexamethyleneimine > Me2NH > pyrrolidine probably reflects the decrease in steric bulkiness of amines. (f) Although primary amines are in general not suitable for the double carbonylation, tert-butylamine can be used because of its inertness to the product α-keto amide.Reactivity of trans-PdPh(I)(PMePh2)2 and trans-Pd(COPh)I(PMePh2)2, supposed intermediates in the catalytic reaction of PhI, toward amines and CO was examined.The relative reactivity of six secondary amines with the benzoylpalladium complex increasing in the order Pr2NH Et2NH piperidine Me2NH hexamethyleneimine pyrrolidine was found to be inversely correlated with decreasing selectivity order for α-keto amide formation in the catalytic systems.On the basis of the experimental results, a mechanism consisting of two catalytic cycles to produce α-keto amides and amides has been proposed.