ChemInform Abstract: RAPID REVERSIBLE INTRAMOLECULAR MIGRATIONS OF GROUPS COUPLED WITH NUCLEOPHILIC CENTERS ACROSS CARBON ATOMS. IX. PHOTOINITIATED ACYLOTROPIC REARRANGEMENTS

Abstract

Die bei Kondensationen der Na‐Salze der Azomethine (I) mit Säurechloriden entstehenden N‐Acyl‐Verbindungen (II) gehen unter der Einwirkung von langwelligem Hg‐Licht in Benzol, Aceton oder DMF praktisch quantitativ in die O‐Acyl‐ Tautomeren (III) über (UV‐, IR‐Spektrum; Kinetik).

Dissociative and Photochemical Mechanisms of Intramolecular Tautomerism

“…This is explained by an unfavored orientation of the interacting orbitals of the electron lone pair in nitrogen and the carbonyl group [36,37). An analogous method for the initiation of acyl transfers has been used by Hartke and coworkers [39][40][41][42] The same basic reaction scheme was found [23,43,44] to operate in photoinitiated acylotropic rearrangements of N-acylaminomethylene derivatives of 3(2H)benzo( b )thiophenones and their analogs XVlIa. However, the rearrangement XVa ~ XVb proceeds rapidly and completely upon UV irradiation of solutions of XVa, leading to the intermediate formation of the E-isomer XVc, whose structure meets the steric requirements of the 1,3-acyl transfer reaction.…”

“…An analogous mechanism with only singlet excited states is, apparently, operative also in the photoinitiated reaction of the ° ~ N transfer of the acetyl group [23]. Upon absorption of (hvl) in the long-wave-band region of the electronic spectrum of IXa (340 nm), the molecule comes to be in the vibrationally excited region of the first single state of IXb, and on emission of the quantum hv 2 , by which the presence of the tautomer IXb can be established, or through a radiationless transition, this molecule, after overcoming an insignificant activation barrier /);.E: ~ b' returns to the stable form IXa.…”