73078-76-9Relevant academic research and scientific papers
Azastilbenes. 2. Photodimerization
Vansant, J.,Toppet, S.,Smets, G.,Declercq, J. P.,Germain, G.,Meerssche, M. Van
, p. 1565 - 1573 (1980)
The photochemical behavior of several azastilbenes has been followed in concentrated solution and in the solid state.In acetonitrile and benzene isomerization and dimerization occur, the reactions being generally faster in acetonitrile.In methanol, however, photoreduction as well as photoaddition of the solvent intervene and are important processes.With irradiation in the solid state, dimerization occurs only for some azastilbenes and their quaternary salts, depending on the orientations of the molecules within the crystal lattice and the distances between adjacent double bonds (3.5-4.2 Angstroem).X-ray analysis has shown that trans-1,2-di(2-pyrazinyl)ethylene crystallizes in two distinct modifications of which only one has a crystal stacking suitable for topochemical dimer formation.The dimers were characterized by 1H and 13C NMR, IR, and mass spectroscopy.The crystalline and molecular structures of five of them were determined by X-ray diffraction, namely cyclobutane dimers of 1,2-di(4-pyridyl)ethylene, 1,2-di(2-pyridyl)ethylene, 1,2-di(2-pyrazinyl)ethylene (all three r-ctt dimers), and 1-(3-pyridyl)-2-(2-pyrazinyl)ethylene (r-ctt head-to-head and head-to-tail dimers).
[2+2] Photodimerization of bispyridylethylenes by a controlled shift of the protonation equilibrium
Yamada, Shinji,Kusafuka, Momoko,Sugawara, Mai
supporting information, p. 3997 - 4000 (2013/07/25)
Irradiation of trans-4,4′-bispyridylethylene in the presence of 1 equiv of concd HCl produced a syn dimer with high selectivity, whereas irradiation in the presence of more than 2 equiv of concd HCl or in the absence of HCl gave a mixture of dimers and by-products with much lower selectivity. This indicated that a suitable amount of acid served as a catalyst for the [2+2] photodimerization of BPEs through cation-π interactions between the pyridinium and pyridine rings.
Pyridyl-substituted Cyclobutanes via Photodimerisation of Azastilbenes
Horner, Michael,Huenig, Siegfried
, p. 1183 - 1210 (2007/10/02)
Mono- and diazastilbenes A1 - A9 as well as their mono- and dihydro- or -alkyl quaternary salts are irradiated (UV).Mono salts are smoothly converted into cyclobutanes C in crystalline state and/or in solution.The free bases A or their bis salts, reacting in solution only, from partly or exclusively different products.Their structures together with the constitutions and configurations of the cyclobutanes A are elucidated.Results from the literature are partly confirmed and partly corrected.
