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Irradiation of the 9-formyl-, 9-acetyl-, 9-nitro- and 9-tent-substituted dibenzobarrelenes gave the corresponding 4b-substituted dibenzosemibullvalenes, (2a) (8b,8c-dibenzoyl-4b,8b,8c,8d-tetrahydrodibenzo[a,f]-cyclopropa[cd]pentalene-4b-carbaldehyde, C 31 H 20 O 3 ), (2b) (4b-acetyl-8b,8c-dibenzoyl-4b,8b,8c,8d-tetrahydrodibenzo[a,f]cyclopropa[cd]pentalene, C 32 H 22 O 3 ), (2c) (8b,8c-dibenzoyl-4b-nitro-4b,8b,8c,8d-tetrahydrodibenzo[a,f]cyclopropa[cd]pentalene, C 30 H 19 NO 4 ) and (2d) (8b,8c-dibenzoyl-4b-tert-butyl-4b,8b,8c,8d-tetrahydrodibenzo[a,f]cyclopropa[cd]pentalene). The product (2d) gave the corresponding dibenzopentalenofuran derivative, (3d) (10c-benzoyl-6b-tert-butyl-2-phenyl-10b,10c-dihydro-6bH-dibenzo[a,f]furo[2,3,4-cd]pentalene, C 34 H 28 O 2 ). The structures of (2a), (2b), (2c) and (3d) have been established unequivocally via X-ray crystallographic analysis. The molecular structures of (2a), (2b), and (2c) incorporate the basic dibenzosemibullvalene skeleton, which contains the 6:5:5:6:3 fused ring system with normal bond lengths and bond angles. The crystal structures of (2a), (2b), and (2c) have intermolecular hydrogen-bonding interactions (< 2.60 A) which are almost linear around the H atoms. The structure of (3d) shows a 6:5:5:6:5 fused ring system and does not indicate hydrogen-bonding-type intermolecular interactions. |
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