Control of Metal-Catalyzed Reactions by Organic Ligands: From Corrinoid and Porphinoid Metal Complexes to Tailor-Made Catalysts for Asymmetric Synthesis.
Corrinoid and porphinoid metal complexes playa fundamental role in nature as catalysts for a variety of biochemical transformations. The properties of the metal ion in these complexes are strongly influenced by the macrocyclic ligand. In this way, the reactivity of the metal complex is adjusted to the specific requirements of enzymatic catalysis. This is illustrated in the first part of this article, which is centered on the structure and properties of coenzyme F430, a hydroporphinoid nickel complex involved in the methane-producing step of the energy metabolism of methanogenic bacteria. A different group of metal complexes, which exemplify the concept of ligand-based selectivity control, is discussed in the second part, summarizing our work on enantioselective catalysis. Inspired by the structure of corrinoid and hydroporphinoid compounds, we have developed a route to chiral C2-symmetric semicorrins, a particular class of bidentate nitrogen ligands specifically designed for the stereocontrol of metal-catalyzed reactions. Semicorrins were found to induce remarkable enantioselectivities in the cobalt-catalyzed conjugate reduction of α,β-unsaturated carboxylic esters and amides and in the copper-catalyzed cyclopropanation of olefins with diazo compounds.
Andreas
A
Pfaltz