Fluorene, structure

Fig-i Fluorene structure showing numbering of sites available for substitution, as well as an illustration of the decoupling provided by bonding groups to its 9-position... 

Cook Utilized an atypical selenium dehydrogenation of a partially saturated keto-derivative to afford pyrene in 1934 [35). Cook and coworkers also successfidly synthesized several new polycycles and numerous derivatives through the process of their research. A few examples of novel systems produced include new isomers of benzopyrene, anthraceneotetraphene 35, benzopentaphene 36, dibenzanthracene 37, as well as several condensed fluorene structures such as 38 and 39 (Fig. 1.4) [36], Cook s formation of cydopentenophenanthrene 40, an important phenan-threne derivative used to produce several active natural products, was an early highlight of his career [37],... 

The excited triplet states of quinones can be fairly readily populated by irradiation and nuclear polarization observed (Cocivera, 1968). Hydrogen atom abstraction leads to the relatively stable semiquinone radicals and, in alkaline media, radical anions. Recombination of radical pairs formed in this way can give rise to CIDNP signals, as found on irradiation of phenanthraquinone (20) in the presence of donors such as fluorene, xanthene and diphenylmethane (Maruyama et al., 1971a, c Shindo et al., 1971 see also Maruyama et al., 1972). The adducts are believed to have the 1,2-structure (21) with the methine proton appearing in absorption in the polarized spectrum, as expected for a triplet precursor. Consistently, thermal decomposition of 21 as shown in equation (61) leads to polarization of the reactant but now in emission (Maruyama... 

Figure 7.23 shows the prototype diazobenzo[Z ]fluorene-based natural products kinamycin A and prekinamycin. The kinamycin A-D family were first isolated from Streptomyces murayamaensis, but the structures were incorrectly characterized as having a cyanobenzo[Z ]carbazole ring. Since the initial discovery of the kinamycins, many new analogues have been discovered from natural sources.88-92... 

Charge-transfer adducts are formed with the gold(I) trimers [Au3(MeN=COR)3] (R = Me, Et), which act as electron donors, and organic electron acceptors as nitro-9-fluorenes. The structures of these adducts involve mixed stacks in which the gold trimers and the planar nitro-fluorenes are interleaved.3130 No luminescence has been observed from these solid charge-transfer adducts, which is not surprising since the luminescence of [Au3(MeN=COR)3] is a property that is associated with the supramolecular organization in the solid. 

The matter was settled in 1994 in back-to-back communications by Gould [12] and Dmitrienko [13]. Gould showed that treatment of natural prekinamycin with dirhodium tetraacetate in methanol yielded the fluorene 16 (Scheme 3.1). The vinyl proton formed in this reaction (H-l) provided a critical spectroscopic handle and allowed unambiguous determination of the carbocyclic structure, excluding the presence of an indole heterocycle. In parallel, his research group obtained a high-quality crystal structure of a kinamycin derivative. The refined data set was shown to best accommodate a diazo rather than cyanamide (or isonitrile) function. 

Figure 14 The structure of 9-bromo-9-[(bromomagnesium)methylene]fluorene 30. 

Type 61b of the intensely colored quinocyclopropenes is represented by the di-cyanomethylene species 115 and 118 of p- and o-quinonoid structure. In addition to the systems 115,119, and 122 reported by Gompper1001 a series of o- and p-quino-cyclopropenes in the benzene, naphthalene, anthracene, phenanthrene, and fluorene series (718-125) were prepared75) carrying the bis-(p-anisyl)-cyclopropenyl residue, which brings about a better stabilization of the cyclopropenium moiety101 ... 

Intramolecular Friedel-Crafts reactions can sometimes compete with organosil-icon hydride reductions of benzylic-type alcohols to cause formation of undesired products. An example is the attempted reduction of alcohol 26 to the corresponding hydrocarbon. When 26 is treated with triethylsilane in trifluoroacetic acid at room temperature for 15 hours, a mixture of the two fluorene isomers 27 and 28 is obtained in a combined yield of 45%. None of the hydrocarbon structurally related to the substrate alcohol 26 is obtained.171 Whether this problem could be circumvented by running the reduction at a lower temperature or with a different acid remains subject to experimentation. 

Boyle, T.P., S.E. Finger, R.L. Paulson and C.F. Rabeni. 1985. Comparison of laboratory and field assessment of fluorene. Part II. Effects on the ecological structure and function of experimental pond ecosystems. Pages 134-151 in T.P. Boyle (ed.). Validation and Predictability of Laboratory Methods for Assessing the Fate and Effects of Contaminants in Aquatic Ecosystems. ASTM STP 865. American Society for Testing and Materials, Philadelphia, PA. 

Kinamycin Antibiotics Revised Structures as Diazobenzo[b]fluorenes. . 137... 

A series of publications elucidating the correct structure of kinamycins A, B, C, and D as 5-diazobenzo[fr]fluorenes (7a-f, Fig. 13), have appeared in the literature [41,42], The earlier assignment of these antibiotics as benzolfr]carbazoloquinonccynamides [40] (Fig. 14) was discarded upon mismatch of the synthesized structure with the natural products. While most of them are known to possess antibacterial activity, some have shown considerable toxicity to cancerous cells [44,46,47]. 

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