N-ヘテロ芳香族の電子的性状 : 第27報 2,4,および6位フッ素置換ピリミジン誘導体の^<19>F核磁気共鳴スペクトル

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Fluorine nuclear magnetic resonance (NMR) spectra of the following derivatives of pyrimidine (Py) at 60 Mcps in dimethyl sulfoxide, with trifluoroacetic acid as internal standard, have been obtained and examined : 2,4,6-trifluoro-Py (I), 4-amino-2,6-difluoro-Py (II), 4-amino-2,6-difluoro-5-methyl-Py (III), 4-amine-2-fluoro-6-methyl-Py (IV), 4-amino-2-fluoro-5,6-dimethyl-Py (V), 6-fluoro-4-hydroxy-5-methyl-Py (VI), 4-amino-6-fluoro-5-methyl-Py (VII), 2-amino-4-fluoro-6-methyl-Py (VIII), 2-amino-4,6-difluoro-Py(IX), 2-amino-4,6-difluoro-5-methyl-Py(X), 6-fluoro-4-hydroxy-2-methyl-Py (XI), 4-amino-6-fluoro-2-methyl-Py (XII), 6-fluoro-4-hydroxy-2,5-dimethyl-Py (XIII), 4-amino-6-fluoro-2,5-dimethyl-Py(XIV), 4,6-difluoro-2-phenyl-Py(XV), 4,6-difluoro-5-phenyl-Py(XVI), 4-amino-6-fluoro-2-phenyl-Py(XVII), and 4-amino-6-fluoro-5-phenyl-Py(XVIII). ^<19>F signals of these compounds were rather broadened by ^<14>N quadrupolar relaxation. The NMR signals of 2-position fluorines occurred in lower magnetic field (for I-V, δ=-20.05--31.97 ppm) than those of 4-or 6-position fluorines (for VI-XVIII, δ=-0.50-21.79ppm). Discussion was made on the influence of substituents on the 2- as well as 4(6)-fluorine chemical shifts. It was revealed that substituent effects were expressed more markedly in the ^<19>F NMR spectra than in the ^1H NMR spectra of the corresponding non-fluorinated compounds. Smaller spin-spin coupling constants were obtained for J_4(6)F-_5H (I, II, VIII, IX, and XII, J=1.3-3.3 cps) than for J_2F-_5H(IV, J=4.7 cps). An approximate parallelism was found to exist between ^<19>F chemical shifts and electron densities at the carbon atoms adjacent to fluorines.
公益社団法人日本薬学会の論文
1968-09-25

N-ヘテロ芳香族の電子的性状 : 第27報 2,4,および6位フッ素置換ピリミジン誘導体の^<19>F核磁気共鳴スペクトル

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