Hori, Tetsuharu Otani, Yuko Kawahata, Masatoshi Yamaguchi, Kentaro Ohwada, Tomohiko Nonplanar Structures of Thioamides Derived from 7-Azabicyclo[2.2.1]heptane. Electronically Tunable Planarity of Thioamides X-ray crystallographic analysis showed that <i>N</i>-thiobenzoyl-7-azabicyclo[2.2.1]heptane displays marked nonplanarity of the thioamide (<b>1a</b>, α = 167.1° and |τ| = 11.2°) as compared with the corresponding monocyclic pyrrolidine thioamide (<b>2a</b>, α = 174.7° and |τ| = 3.9°). In a series of <i>para</i>-substituted or unsubstituted thioaroyl-7-azabicyclo[2.2.1]heptanes (<b>1a</b>−<b>1h</b>), the planarity of the thioamide depended significantly on the electronic nature of the substituent; for example, in the <i>p</i>-nitro-substituted compound, planarity was substantially restored (<b>1h</b>, α = 175.2° and |τ| = 0.1°). In solution, increasing electron-withdrawing character of the aromatic substituent was associated with a larger rotational barrier of the bicyclic thioamides, as determined by means of variable-temperature <sup>1</sup>H NMR spectroscopy and line shape analysis. The reduced rotational barrier, that is, reduced enthalpy of activation (Δ<i>H</i><sup>⧧</sup>) for thioamide rotation, of <b>1a</b> as compared with that of <b>2a</b> in nitrobenzene-<i>d</i><sub>5</sub> is consistent with the postulate that <b>1a</b> assumes a nonplanar thioamide structure in solution. These results indicate that the planarity of thioamides based on 7-azabicyclo[2.2.1]heptane is controlled by electronic factors in the solid phase and in solution. thioamide rotation;Thioamides Derived;bicyclic thioamides;solution;planarity;nonplanar thioamide structure;NMR;Nonplanar Structures;line shape analysis 2008-11-21
    https://acs.figshare.com/articles/journal_contribution/Nonplanar_Structures_of_Thioamides_Derived_from_7_Azabicyclo_2_2_1_heptane_Electronically_Tunable_Planarity_of_Thioamides/2898388
10.1021/jo801996b.s001