Ring Closure and Ring Expansion Reactions in Bridged Triarylphosphanes and Triarylarsanes with <i>o</i>‐Isopropenyl Substituents. Novel Candidates for Turnstile Geometry

Abstract

ortho-Cyclizations to C3r polycycles 1 and novel ring expansions by three ring members takes place on acid treatment of the 2,6-diisopropenylphenyl derivatives 2. The pentacoordinated o-chloranil adduct of 1 (Y = P) does not exhibit ideal turnstile geometry, but a distorted trigonal-bipyramidal structure.