(Z)- and (E)-Arylidene-1,3-dihydroindol-2-ones: configuration, conformation, and infrared carbonyl stretching frequencies

Abstract

The configuration and conformation of both (Z)- and (E)-arylidene-1,3-dihydroindol-2-ones were investigated. In the solid state the Z-isomer is planar whereas the E-isomer has the aryl group significantly twisted, as shown by two X-ray structures. A linear correlation was found between _(co) and the σ_p⁺ of the substituents and this allows the conformation in solution and the degree of conjugation of the Ar–CC–CO system to be inferred.