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[摘要]：(Heterocyclic Compounds (One Hetero Atom)) Section 7,7'-Dihydroxy-8,8'-biquinolyl and 2,2'-di-tert-butyl-7,7'-dihydroxy-8,8'-biquinolyl were O,O'-dialkylated with MeI or dihaloalkanes [X(CH2)nX', n = 1, 3 - 6]. The resulting diethers, e.g. I [R = H, tert-Bu, Y = (CH2)n, n = 1, 3], were characterized by UV spectroscopy and (wherever possible) single-crystal X-ray diffraction anal. Biquinolyl basicity was found to pos. correlate with interannular dihedral angle (IDA). Two pKa points could be located for all biquinolyl diethers with IDA above ca. 65?(pKa1 2.3-2.7; pKa2 4.5-5.3 in aq MeOH). By contrast, methylene diethers (IDA ?60? were only very weakly basic (pKa 2.7-3.1) and could not be doubly protonated. Lone-pair/lone-pair proximity effects are invoked to account for the observations. |
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