Conformation and stereodynamics of the oxepine ring system
Abstract
Low temperature n.m.r. studies on 2-cyano- and 2-ethoxycarbonyl-7-ethyloxepine establish a non-planar ring geometry with a ring inversion barrier of 6.5 kcal mol–1(27.2 kJ mol–1), and provide evidence of a rotational isomerism involving the 2-ethoxycarbonyl substituent; an X-ray crystallographic analysis of 2-t-butoxycarbonyloxepine confirms the non-planar boat geometry.