Effect of Through‐Bond Interaction on Conformation and Structure in Rod‐Shaped Donor–Acceptor Systems. Part 1

The crystal structures of five N‐arylpiperidin‐4‐one derivatives 2P2, 3P2, 5P2, 1P3 , and 2P3 are presented (Fig. 2 and Tables 1–5) and discussed together with the derivatives 1P2 and 4P2 published previously. In all but one structure, 1P2 , the aryl group is in an equatorial position. The piperidine ring adopts a normal chair conformation. In 1P2 , the piperidine ring central C? C bonds are significantly elongated, which is consistent with the idea that through‐bond interaction is more pronounced in the axial conformation. Through‐bond interaction also influences the pyramidalization at the piperidine C(4)‐atom in such a way that a strong interaction is directing the ethylene C‐atom C(9) into the axial direction.