Catalytic Formation of Amides
Abstract: The amide functionality is a highly important chemical bond, found in a great number of synthetic products such as pharmaceuticals, polymers and agrochemicals. The focus of this thesis has been directed towards efficient, mild and environmentally friendly methods for amide formations. The first part is devoted to the investigation of a Lewis acid catalyzed protocol for direct condensation of non-activated carboxylic acids and amines. ZrCl4 was found to be a highly active catalyst and a low catalytic loading enabled for high yields of secondary and tertiary amides under relatively mild conditions. The second part of the thesis describes our investigations towards a catalytic method for primary amides. We demonstrated that the transformation was feasible by performing minor alterations to the previous Lewis acid based procedure. A variety of primary amides could be obtained in high yields by the use of carbamates, as a non-gaseous source of ammonia in combination with carboxylic acids and catalytic amounts of TiCl4 or ZrCl4. Furthermore, the protocol was extended to include catalytic formation of N,N-dimethylamides from non-activated carboxylic acids.The use of immobilized metal nanoparticles as heterogeneous catalysts has emerged as a highly investigated research area. The final chapter of this thesis deals with the successful application of an immobilized Pd nanocatalyst for amide formation via the aminocarbonylation reaction of aryl iodides. The Pd0-AmP-MCF catalyst was found to operate through a “release and catch” mechanism, in which PdII species were released into the solution and then re-deposited onto the support after completion of the reaction. It was discovered that the combination of aryl halide and amine was the cause of the leaching, and furthermore that the homogeneous Pd species catalyzed the aminocarbonylation reaction. A selection of aryl iodides were evaluated using 2 mol% of Pd0-AmP-MCF under atmospheric pressure of CO, and the corresponding amides were obtained in good to high yields.
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