Photoisomerization of Tetraethyl 6,8,15,17-Tetrahydro-7H,16H-5,18-benzeno-9,14-ethenodibenzocyclotetradecene-7,7,16,16-tetracarboxylate. Structure of Tetraethyl 2,3,3a,7b,9,10,10a,14b-Hexahydro-1H,8H-3a,7b-benzeno-10a,14b-ethenodibenzo dicyclopentacycloocte..

Article abstract of DOI:10.1107/S0108270193014064

The initially formed cyclophane product, tetraethyl 6,8,15,17-tetrahydro-7H,16H-5,18<1',2'>-benzeno-9,14-ethenodibenzocyclotetradecene-7,7,16,16-tetracarboxylate (I), produced from the cyclization of 9,10-bis<<2,2-di(ethoxycarbonyl)>ethyl>anthracene by treatment with sodium hydride followed by 1,4-bis(bromomethyl)naphthalene, was completely isomerized into its intramolecular <4?s + 4?s> cycloaddition product, tetraethyl 2,3,3a,7b,9,10,10a,14b-hexahydro-1H,8H-3a,7b<1',2'>-benzeno-10a,14b-ethenodibenzodicyclopentacyclooctene-2,2,9,9-tetracarboxylate (II), when passed through a silica gel column under fluorescent light.The crystal structure analysis of (II) as its methylene chloride solvate showed that the length, 1.65 (1) Angstroem, of each central bond, C3a-C14b and C7b-C10a, is larger than expected, and that the five-membered rings are exceptionally puckered.