Aromatic propellenes. Part 10. Conformational study of hexa(imidazol-1-yl)benzene and hexakis(2-methylimidazol-1-yl)benzene by means of NMR and AM1 calculations

Hexa(imidazol-1-yl)benzene, (imz)(6)bz, and hexakis(2-methylimidazol-1-yl)b enzene, (mimz)(6)bz, have been synthesized from hexafluorobenzene and imida zole or 2-methylimidazole anions in tetrahydrofuran. The stabilities of the eight possible conformers of (imz)6bz and (mimz)(6)bz have been estimated by semi-empirical calculations at the AMI level. In both compounds, the abs olute minimum corresponds to the conformation in which the beta nitrogen lo ne pair of consecutive imidazole rings is alternately oriented to opposite sides of the benzene plane. While in (imz)(6)bz only the ring signals corre sponding to a unique imidazole were observed, the presence of the eight con formers in (mimz)(6)bz has been established by H-1 and C-13 NMR spectroscop y. (C) 1999 Elsevier Science B.V. All rights reserved.