Photochemical Reaction of 2,3-Dipyrazine Derivatives in the Crystalline State and in Solution

Article abstract of DOI:10.1246/bcsj.66.2987

The photoreaction of 2,3-di<(E)-styryl>pyrazine derivatives was carried out in the crystalline state and in solution.Among them, 2,3-di(p-chlorostyryl)pyrazine an d2,3-di(p-cyanostyryl)pyrazine were photoreactive in the crystalline state and gave, upon photoirradiation, <2.2>orthocyclophanes in 76 and 58percent yields, respectively.Such a topochemical photo- behavior was interpreted on the basis of X-ray crystllographic analyses of the crystals.The photoirradiation of 2,3-distyrylpyrazine in solution gave <2.2>orthocyclophane and anti head-to-tail type monocyclic dimer as the major products.The yields of the products varied depending on the solvent; with decreasing the polarity of the solvent, the yield of the cyclophane decreased, whereas the yield of the monocyclic dimer increased.In a similar manner, the photoirradiation of the other 2,3-distyrylpyrazine derivatives in acetonitrile/chloroform (10/1) or acetonitrile gave the corresponding <2.2>orthocyclophanes and monocyclic dimers, respectively, as major products through two types of excimers.