Abstract:The reaction of dicyanoacetylene (DCA) with the partially hydrogenated dimethano-bridged anthracene and pentacene derivatives 3 and 18 lead to the (1:1) Diels ± Alder adducts 5 and 19, respectively, and to the 9,10-dihydronaphthalene derivatives 6 and 21, respectively. These compounds are intensely colored, most likely due to a charge-transfer absorption. Photolysis of the (1:1) adducts 5 and 19 produces the corresponding cyclooctatetraene derivatives 7 and 8, which are not planar despite the torsional constraints caused by the fusion of the eight-membered ring to norbornane and norbornene units. The mechanisms of formation of the dihydronaphthalene derivatives 6 and 21 were elucidated by the use of high pressure; this allowed the (2:1) adducts 11 and 20 to be detected as intermediates in the reaction of DCA with 5 or 19 to give 6 and 21, respectively. A degenerate rearrangement consisting formally of a [1,5] The finding that the irreversible rearrangement of 6 accompanied by the elimination of HCN to give the azulene derivative 14 proceeds only on heating of 6 to 80 8C in a polar solvent is good evidence for a polar mechanism in this case.
Belowground ecosystems are accessible by mining, where a specific microbial community can be discovered. The biodiversity of a former alum mine rich in carbon, but with a low pH of 2.6–3.7, was evaluated by DNA- and cultivation-dependent methods using samples of the black slate rock material, secondary mineralization phases and seepage water. Pyrite oxidation within the low-grade metamorphic Silurian black slate established high concentrations of Fe and $\rm{SO}_4^{2-}$ forming the extreme conditions visible with acidophilic and Fe-oxidizing microorganisms. In addition, an unexpected predominance of fungi in this C-rich and acidic cave ecosystem, including high numbers of Mucoromycota and Mortierellomycota, was detected. Therefore, fungal cultures were obtained, mainly from the secondary mineral phases that are iron phosphates. Hence, the fungi might well have been involved in phosphate mobilization there. The rock material itself is rich in organic carbon that can be used by oxidase activity. The cultivation setup mimicked the cave conditions (low temperature, low pH, oxic conditions), with one oligotrophic and one medium rich in nutrients that allowed for isolation of different fungal (and eutrophic bacterial) groups. The acidic conditions prevented the occurrence of many basidiomycetes, while the isolated fungi could survive these adverse conditions.
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