885686-99-7Relevant academic research and scientific papers
Conformational properties of C2v-symmetrical resorcin[4]arene tetraethers
Morikawa, Osamu,Iyama, Eiichi,Oikawa, Tomoyoshi,Kobayashi, Kazuhiro,Konishi, Hisatoshi
, p. 214 - 218 (2007/10/03)
Resorcin[4]arene tetraether derivatives, in which a resorcinol unit and a 1,3-dialkoxybenzene unit are incorporated in an alternating order, were synthesized by the Sc(OTf)3 catalyzed '2 + 2' fragment condensation. The conformational properties were studied using variable temperature 1H-NMR spectroscopy, indicating that the resorcinarenes are flexible at room temperature but frozen in the cone formation at -90°C in CD 2Cl2, and they interconvert between two equivalent cone conformations with an energy barrier of ΔGc? = 10.2-10.5 kcal mol-1. These values are slightly lower than that for the resorcin[4]arene containing four 2-hexylresorcinol units. The cone conformation is stabilized by intramolecular hydrogen bonds between the OH hydrogen and ether oxygen, which is evidenced by the low frequencies (3423-3434 cm-1) of the OH-stretching vibrations in CDCl3 solution. Copyright
