σ, π‐Isomerisierungen von Monohetero‐σ‐bishomobenzol‐Derivaten. Vorläufige Mitteilung

The cis-oxa- (13a-d) and -aza-σ-bishomobenzene (13 e) derivatives have been synthesized; they are sufficiently stable to be isolated in pure form. On heating, 13a-e are easily isomerized into the π-bishomobenzene analogues 14a-e, the processes 13 a ⇄ 14 a, 13 b ⇄ 14b and 13d ⇄ 14d being reversible. Some kinetic and thermodynamic data for these σ, π,bishomobenzene transformations are presented.