Synthesis of enantiopure planar chiral bis‐(para)‐pseudo‐meta‐type [2.2]paracyclophanes |
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| Authors: | Risa Sawada Masayuki Gon Jun Nakamura Yasuhiro Morisaki Yoshiki Chujo |
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| Institution: | 1. Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan;2. Department of Applied Chemistry for Environment, School of Science and Technology, Kwansei Gakuin University, Sanda, Japan |
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| Abstract: | A new type of planar chiral (Rp)‐ and (Sp)‐4,7,12,15‐tetrasubstituted 2.2]paracyclophanes was prepared from racemic 4,7,12,15‐tetrabromo2.2]paracyclophane as the starting substrate. Regioselective lithiation and transformations afforded racemic bis‐(para)‐pseudo‐meta‐type 2.2]paracyclophane (4,15‐dibromo‐7,12‐dihydroxy2.2]paracyclophane). Its optical resolution was performed by the diastereomer method using a chiral camphanoyl group as the chiral auxiliary. The diastereoisomers were readily isolated by simple silica gel column chromatography, and the successive hydrolysis afforded (Rp)‐ and (Sp)‐bis‐(para)‐pseudo‐meta‐type 2.2]paracyclophanes ((Rp)‐ and (Sp)‐4,15‐dibromo‐7,12‐dihydroxy2.2]paracyclophanes). They can be used as pseudo‐meta‐substituted chiral building blocks. |
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| Keywords: | chiral auxiliary chiral building block diastereomer optical resolution regioselectivity |
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