Majority‐Rules‐Type Helical Poly(quinoxaline‐2,3‐diyl)s as Highly Efficient Chirality‐Amplification Systems for Asymmetric Catalysis |
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| Authors: | Dr Tetsuya Yamada Prof?Dr Michinori Suginome |
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| Affiliation: | 1. Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo‐ku, Kyoto 615‐8510 (Japan);2. JST, CREST, Katsura, Nishikyo‐ku, Kyoto 615‐8510 (Japan) |
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| Abstract: | A highly efficient majority‐rules effect of poly(quinoxaline‐2,3‐diyl)s (PQXs) bearing 2‐butoxymethyl chiral side chains at the 6‐ and 7‐positions was established and attributed to large ΔGh values (0.22–0.41 kJ mol?1), which are defined as the energy difference between P‐ and M‐helical conformations per chiral unit. A PQX copolymer prepared from a monomer derived from (R)‐2‐octanol (23 % ee) and a monomer bearing a PPh2 group adopted a single‐handed helical structure (>99 %) and could be used as a highly enantioselective chiral ligand in palladium‐catalyzed asymmetric reactions (products formed with up to 94 % ee), in which the enantioselectivity could be switched by solvent‐dependent inversion of the helical PQX backbone. |
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| Keywords: | asymmetric amplification asymmetric synthesis helical structures ligand design polymer catalysts |
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