Iridium-katalysierte enantioselektive allylische Substitution mit nicht-aktivierten Carbonyl-Nucleophilen

• Applicant: Professor Dr. Timm Graening
• Subject Area: Organic Molecular Chemistry - Synthesis and Characterisation
• Term: Funded in 2005
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5452769

Enantioselective allylic substitution reactions have advanced to a highly valuable tool in synthetic organic chemistry and the further development of this methodology currently forms a very active area of research. High levels of enantioselectivities have been reached and catalytic systems for the most part Palladium catalysts have been developed for a variety of different substrates. Nevertheless, there are several limitations to the Pd catalysts as for the range of nucleophiles and allylic reaction partners that can be employed. Only recently significant progress has been made by several research groups with catalysts based on Iridium and chiral phosphoramidite ligands. These catalysts have been shown to yield chiral branched substitution products with monosubstituted allylic electrophiles in high enantiomeric excesses, whereas Pd catalysts almost exclusively give linear achiral reaction products. Besides these most promising results there are some indications that unactivated carbonyl nucleophiles can be integrated into this process. Up to now in the vast majority of cases with Pd catalysts extra -activated carbonyl nucleophiles have to be used. With the use of unactivated carbonyl nucleophiles the scope of the allylic substitution methodology would be greatly broadened and furthermore this would allow for the controlled construction of a second stereocenter in the reaction products when prochiral nucleophiles are employed. In the projected research program a detailed study of the enantioselective allylic substitution with unactivated carbonyl nucleophiles an the basis of Ir catalysts with phosphoramidite ligands is to be undertaken, with the goal to develop a reaction process which gives rise to synthetically important Claisen-rearrangement-type reaction products with control over the absolute configuration of the two newly formed stereogenic centers.

• DFG Programme: Research Fellowships
• International Connection: USA
• Cooperation Partner: Professor John F. Hartwig, Ph.D.