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Catalytic Asymmetric Iodocyclization of N‐Tosyl Alkenamides using Aminoiminophenoxy Copper Carboxylate: A Concise Synthesis of Chiral 8‐Oxa‐6‐Azabicyclo[3.2.1]octanes
Authors:Prof?Dr Takayoshi Arai  Ohji Watanabe  Shinnosuke Yabe  Prof?Dr Masahiro Yamanaka
Institution:1. Molecular Chirality Research Center, Synthetic Organic Chemistry, Department of Chemistry, Graduate School of Science, Chiba University, 1‐33 Yayoi, Inage, Chiba 263‐8522 (Japan);2. Department of Chemistry, Rikkyo University, 3‐34‐1 Nishi‐Ikebukuro, Toshima‐ku, Tokyo 171‐8501 (Japan)
Abstract:A newly developed aminoiminophenoxy copper carboxylate ( L7 ‐Cu‐OAc)‐catalyzed asymmetric iodocyclization of N‐Tosyl alkenamides gave O‐cyclized products in good yields with high enantioselectivity. From the O‐cyclized products, a skeletal transformation was succeeded in the synthesis of biologically important chiral 8‐oxa‐6‐azabicyclo3.2.1]octanes. DFT calculations suggested that the acetoxy anion of the L7 ‐Cu‐OAc] acts as a base to generate the anion of N‐Tosyl alkenamide substrates. The exchanged acetic acid reconstructs a new hydrogen‐bonding network between the catalyst and the substrates to accomplish the highly efficient asymmetric O‐iodocyclization of N‐Tosyl alkenamides.
Keywords:asymmetric catalysis  copper  cyclization  DFT calculations  halogenation
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