Products of Photo- and Thermochemical Rearrangement of 19-Membered di- tert -Butyl-Azoxybenzocrown.

The preparation and characterization of products of the photochemical and thermochemical rearrangements of 19-membered azoxybenzocrowns with two, bulky, tert -butyl substituents in benzene rings in the para positions to oligooxyethylene fragments ( meta positions to azoxy group, i.e., t -Bu-19-Azo-O have been presented. In photochemical rearrangement, two colored typical products were expected, i.e., 19-membered o -hydroxy- m,m '-di- tert -butyl-azobenzocrown ( t -Bu - 19- o -OH ) and 19-membered p -hydroxy- m,m '-di- tert -butyl-azobenzocrown ( t -Bu - 19- p -OH ). In experiments, two colored atypical macrocyclic derivatives, one 6-membered and one 5-membered ring, bearing an aldehyde group ( t -Bu-19-al ) or intramolecular ester group ( t -Bu-20-ester ), were obtained. Photochemical rearrangement led to one more macrocyclic product being isolated and identified: a 17-membered colorless compound, without an azo moiety, t -Bu-17- p -OH . The yield of the individual compounds was significantly influenced by the reaction conditions. Thermochemical rearrangement led to t -Bu-20-ester as the main product. The structures of the four crystalline products of the rearrangement- t -Bu - 19- o -OH , t -Bu - 19- p -OH , t -Bu-20-ester and t -Bu-17- p -OH -were determined by the X-ray method. Structures in solution of atypical derivatives ( t -Bu-19-al and t -Bu-20-ester ) and t -Bu - 19- p -OH were defined using NMR spectroscopy. For the newly obtained hydroxyazobenzocrowns, the azo-phenol⇄quinone-hydrazone tautomeric equilibrium was investigated using spectroscopic methods. Complexation studies of alkali and alkaline earth metal cations were studied using UV-Vis absorption spectroscopy. 1 H NMR spectroscopy was additionally used to study the cation recognition of metal cations. Cation binding studies in acetonitrile have shown high selectivity towards calcium over magnesium for t -Bu - 19- o -OH .