Chirale Butadiene 2. Stützeffekte bei der behinderten Rotation in penta- und hexasubstituierten Butadienen

Zusammenfassung

A number of penta- and hexasubstituted butadienes of type A was prepared from (E,E)-1,2,3,4-tetrachloro-1,3-butadiene (8) by the substitution of one or both hydrogen atoms. Barriers to rotation around the central CC single bond of butadienes A having prochiral substituents were determined by 1H-n.m.r spectroscopy. The marked influence of the „outer” substituents upon the height of these barriers (δGmath image = 12.2–17.6 (± 0.3) kcal/mol) is interpreted as a buttressing effect of these groups.