ORGN 783 |
| The Nozaki-Hiyama-Kishi reaction is a powerful tool for C-C-coupling of aldehydes and functionalized alkenes to yield (homo)allylic alcohols. Due to its selectivity and mild conditions it is widely used in the synthesis of complex and highly functionalized molecules. We were among the first to develop an asymmetric catalytic version of this reaction which gives rise to a large number of potential applications in organic synthesis, especially for the preparation of natural products. We elaborated a highly enantioselective catalytic system using novel chromium(II)-salen complexes which enables coupling of structurally diverse aldehydes with allylic as well as vinylic halides. Using C2-symmetric DIANANE (endo,endo-2,5-diaminonorbornane) as a chiral backbone, we synthesized a number of novel salen ligands 1 and tested their performance in the reactions (A) and (B) shown here. Furthermore, we would like to report our achievements in the utilization of metal salts as additives which significantly improved the reaction rates and selectivities. These conditions were applied to a number of substrates and yielded outstanding results. In particular, the coupling of vinylic halides and triflates, which so far has only been little investigated, could be considerably improved. We expect this new methodology to be of high synthetic value for a number of diverse applications.
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Asymmetric Reactions, Molecular Recognition, Self Assembly, Bioorganic Chemistry, Process R&D
8:00 PM-10:00 PM, Wednesday, 16 March 2005 Convention Center -- Hall D, Poster
Division of Organic Chemistry |
