Novel carbohydrate olefin hybrid ligands in rhodium catalyzed reactions: Challenging substrates in 1,4-additions

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In the first funding period a number of new chiral heterobidendate ligands with an alkene and a phosphite moiety were prepared based on carbohydrates from the chiral pool. These ligands are well accessible, pseudo-enatiomeric hybrid ligands, which were successfully employed in asymmetric rhodium-catalyzed 1,4-additions. Here we plan to investigate in detail asymmetric catalytic 1,4-additions with challenging nucleophiles such as heteroarylboronates by NMR spectroscopy in order to identify and solve occurring problems. Further, problematic electrophiles such as cycloalkenes with an exocyclic acceptor substituent, e. g. cycloalkene-1-carbonitriles, will be employed in the reaction. On this basis the synthesis of various medicinal drugs, e. g. (-)-paroxenine, will be achieved. In addition, the so far unprecedented asymmetric catalytic 1,4-addition at C2-substituted cyclopentenes will be investigated for synthesizing the steroid hormone equilenine. 1,4-Additions at 1,3-dioxin-4-one are unknown and will be scrutinized as a new access to 3-hydroxycarbonyl compounds. Finally orienting experiments with a combination of the two project lines will be undertaken.