Fluorenone preparation

By analogy, thermal cyclization was described also for 6-nitro-2 -hydroxy-biphenyl-2-carboxylic acids, e.g. 14, obtained by other methods. The same product 15 was also formed from lactone 17, prepared by oxidation of fluorenone 16 (Scheme 2). If the reaction was performed in DMF, the corresponding dimethylamide was isolated (82KGS703, 86KGS852, 87KGS314, 89MI1). 

Fluorenone derived linker 17 prepared in two steps was coupled to aminomethyl-PS via DIPCDI [21]. Due to the presence of an electron-withdrawing carboxamide group, the release of carboxylic acids from this support requires strong acids, such as trifluoromethanesulfonic acid (TFMSA) (Scheme 1). Insertion of an oxygen adjacent to the biphenyl rings to the fluorenone scaffold provides xanthene 18 handle [22]. The oxygen is strategically located to decrease the acid concentration required... 

Patents of Dow Chemicals first described 9,9-diaryl-substituted PF homopolymers 204 and 205 by Yamamoto polymerization of the corresponding 2,7-dibromo monomers [272], although the methods for monomer preparation were not described. For unsubstituted fluorenone, a convenient method for its conversion into 9,9-(4-hydroxyphenyl)-[307-309] and 9,9-(4-alkoxyphenyl)fluorenes [310] was reported previously, which included condensation of fluorenone with phenol or its ethers in acidic conditions (dry HC1 [308,309] or H2SO4 [307,311]) in the presence of (3-mcrcaptopropionic or mercaptoacetic acids. Both polymers 204 and 205 showed similar Mn 21,000 with PDI of 1.48 and 1.75, respectively, and spectral data typical for PF (205 Aabs = 389 (r 50,000 //(mol cm) APL = 417, 439, and 473 mn (THF)) (Chart 2.48). 

The conditions for the photocycloaddition (discussed in detail in a later section of this review) can be relatively mild. There is usually a small probability of the oxetane being destroyed in dark reactions which would probably preclude isolation after preparation by any method. One mode of decomposition of oxetanes is fragmentation, either back to the starting materials or to the other possible carbonyl compound and olefin. For example, the oxetane from 4,4 -dimethoxybenzophenone and isobutylene forms readily and is easily detected and characterized by infrared and NMR spectroscopy. All efforts to purify it, however, have led to its decomposition into formaldehyde and the diarylethy-lene.17 37 In some cases, as with fluorenone and isobutylene37 or 2-methyl-2-butene,25b the oxetane is apparently too unstable for detection, but the presence of the olefin 96 attests to its formation. 

This method has been applied to the preparation of enaminothioketones243 although sometimes the yields are very low (30%)244. The dimerization product is obtained in the reaction of fluorenone with H2S/HCI245, and the pyrolysis of the dimer leads to the hydrocarbon rubicene (equation 21). However, almost quantitative yields of monomeric thiofluorenone can be obtained by performing the reaction at lower temperatures and with higher concentrations of H2S/HCI246. 

The yields of decarbonylation reactions are quite high for bicyclic ketones. When camphor is slowly distilled through a glow discharge some 70-80 per cent of the starting material is converted predominantly to dimethyl-2,1,1-bicyclohexane 20>. Fluorenone decarbonylates to biphenylene almost quantitatively 21>, thus providing a convenient one-step route for the preparation of... 

The products obtained from esters of anthranilic acid and substituted anthranilic acids are of interest because fluorenones can be prepared from them. From diazotized methyl anthranilate and benzene, 2-carbometh-oxybiphenyl is obtained in 24% yield. Hydrolysis affords 2-biphenylcar-boxylic acid, which can be cyclized to fluorenone. By this procedure, a number of 2- and 3-substituted fluorenones have been prepared.16 Thus, 3-chlorofluorenone was prepared from methyl 4-chloroanthranilate and benzene through the following steps. 

Ring closure of w s-o-aminostilbene (XIX) to phenanthrene, o-aminobi-benzyl (XX) to 9,10-dihydrophenanthrene, and o-aminodiphenylmeth-ane (XXI) to fluorene can be effected likewise through the diazoniflm reaction.26 A number of substituted fluorenones have been prepared by this method.26 ... 

Hydrazoic acid attacks the carbonyl and carboxy groups of fluorenone-l-carboxylic acid simultaneously giving mainly 4-amino-phenanthridone together with some acidic material, presumably phenanthridone-4-carboxylic acid.89 The latter is best prepared by prior protection of the carboxy group with pyrrolidine.106 112 The increase in strain associated with the conversion of 4,5-dimethyl-fluorenone into 1,10-dimethylphenanthridone is reflected in the relatively low yield (50%) obtained under Schmidt conditions.22... 

For general synthetic purposes, any of the direct and sensitized photoisomerization routes can be used in the preparation of (E )-stilbenes from the corresponding (Z)-isomers. However, if really pure (Z)-stilbene 90aZ is required, fluorenone sensitization is highly recommended. Otherwise, trace... 

The formyloxy group of cis-8,9a-H-8-formyloxyperhydropyrido[2,l-c][l,4]-thiazin-4-one was hydrolyzed to a hydroxy group and the hydroxy group was oxidized to an oxo group with fluorenone in the presence of ferf-BuOK in benzene at ambient temperature (81EUP34015). 6-Oxoperhydropyrido[2,l-c][l,4]oxazine-4-carboxylic acid was obtained by hydrolysis of the ethyl ester in the presence of LiOH in aqueous THF at 0°C (96MIP8). An amide was prepared from 4-carboxylic acid. 

The natural product was synthesized together with its 8-hydroxy isomer (160) via the cyclization of 4-methyl-2-(3-hydroxyphenyl) nicotinic acid (90). A11 four ring C monohydroxylated onychines have been prepared by a different, unambiguous route and their mass, UV, and H-NMR spectra discussed in detail, showing that the base- and aluminum chloride-induced bathochromic shifts are useful criteria for the location of phenol functions on the benzene ring of aza-fluorenones (97). 

Traditionally cyanohydrins have been prepared by processes that require the establishment of an equilibrium between a ketone and its corresponding cyanohydrin. For many ketones, especially those that are sterically hindered, the position of the equilibrium is unsatisfactory for the effective synthesis of the cyanohydrin. We describe herein a general method for the synthesis of cyanohydrins which does not depend on an equilibrium process. As a result this synthetic procedure can be used to convert a wide variety of dialkyl, diaryl, and arylalkyl ketones into their corresponding cyanohydrins. In addition to the described conversion of benzophenone into its cyanohydrin, acetophenone, fluorenone, tert-butyl phenyl ketone, and a wide variety of aliphatic ketones have been converted into cyanohydrins by this general procedure (Table... 

Molecular complexes, such as the complex formed between poly(N-vinylcaibazole) and 2,4,7-trinitro-9-fluorenone, and dye-polymer aggregates were widely used as generation materials in many early applications. Since these materials are not infrared sensitive, there has been increasing emphasis on pigments. The more widely studied are various azo, phthalocyanine, squaraine, and peiylene diimide derivatives. A common feature of all of these materials is that they are polymorphic and exist in many different crystal forms. The properties are thus very sensitive to the conditions used in their preparation. Further, the sensitivity of these materials is strongly field dependent as well as dependent on the transport material. For a review of generation materials, see Law (1993). 

A halo acid, p-(/S-bromoethyl)-benzoic acid (87%), a hydroxy acid, yS-hydroxyisovaleric acid (9%), and an acetylated amino acid, p-(/3-acetyl-aminoethyl)4>enzoic acid (78%), have been made by this method. Attempts to prepare 3-nitro- and 4-hydroxy-benzoic acids from the corresponding acetophenones have failed. Oxidation of the methylene group of 2-acetylfluorene occurs during the reaction to give fluorenone-2-car-boxylic acid (60%). ... 

Eastman white label 9-fluorenone, m.p. 82-84°, was used. The checkers used material, m.p. 83.5-84.5°, prepared from flu-orene. ... 

The procedure described here is essentially that of Newman and Lutz. 2,4,5,7-Tetranitrofluorenone has been prepared by nitration of fluorenone, 2,4,7-trinitrofluorenone, and 4,5-di-nitrofluorenone. The preparation by Schmidt et al., - which supposedly yielded the 2,3,6,7-isomer, has been shown to yield the 2,4,5,7-isomer. 

The 9-phenyl-9-fluorenyl (PhFl, 118, Scheme 56) amino-protecting group has been proposed by Christie and RapoportF as it is significantly more stable to solvolysis in acid conditions than the trityl group because of the antiaromatic character of the fluorenyl cation. In fact, solvolysis of Trt-Cl is 6000 times faster than PhFl-Cl.f The AI -PhFl amino acid derivatives are prepared with PhFl-Br (commercially available or prepared from fluorenone and phen-yUithium and subsequent substitution with HBr) and lead nitrate, which is required to trap the bromide (Scheme 56).F f2i] lead-free alternative using nitromethane as solvent has also been reported. ... 

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