Formation of novel photodimers from 4-aryl-1,4-dihydropyridines.
N-substituted 3-alkoxycarbonyl-4-aryl-1.4-dihydropyridines have been photochemically investigated for the first time. In contrast to reports of analogous 3,5-dialkoxycarbony] derivatives, they are unreactive in the solid state with shortest distances of potentially reacting double bonds of 6.883(3) A for one derivative examined by x-ray crystal structure analysis. Solution irradiation with unfiltered light (lambda > or = 270 nm) led to novel diazatetrakishomocubanes in 30-50% yields. Diazatetrakishomocubanes were also obtained by irradiation with filtered light (lambda > 313 nm) besides head-to-tail connected syn-dimers. The irradiation of the syn-dimers with unfiltered light led to centrosymmetric cage dimers accompanied by some dimer fragmentation. Formation of the homocubanes via intermediate biradicals is supported by the available data.
Hilgeroth
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Institut für Pharmazeutische Chemie, Halle, Germany. hilgeroth@pharmazie.uni-halle.de
Baumeister
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