Fluorene purification

N,N-Dimethylacetamide (DMAc), 4-fluorobenzoic acid, 4-fluorobenzoyl chloride, aluminum chloride, 1 -bromonaphthalene, nitrobenzene, ferric chloride, dimethyl sulfone, 4,4 -dihydroxybiphenyl (DHB), and potassium carbonate were obtained from Aldrich and used without purification. 4,4-(Hexafluoroiso-propylidiene)-diphenol (6F-BPA), 9,9-bis(4-hydroxyphenyl)fluorene (HPF), and l,l-bis(4-hydroxyphenyl)-l-phenylethane (Bisphenol AP) were obtained from Ken Seika Corporation and used without purification. 4,4 -Dihydroxydiphenyl sulfone (DHDS) was obtained from Nachem Incorporated and used without purification. 

Tetrabenzo[a,c,g,i]fluorene has been used to selectively link synthetic intermediates to charcoal, for the purpose of their purification. In polar solvents, the tetrabenzo-fluorene is strongly adsorbed by charcoal this enables efficient separation of the intermediate from reagents. After centrifugation and washing, the intermediate is displaced from the charcoal and released into solution by addition of a non-polar solvent, and a new synthetic operation in solution can be conducted (Figure 3.43). Tetrabenzo-fluorene has also been used for the purification of peptides [849] and oligonucleotides [850], and for the synthesis of quinolones [851]. 

If technical fluorene (m.p. 103-107°) from Eastman Kodak Company or the Barrett Company is used, much difficulty is experienced in the purification of the product. Technical fluorene can be rendered suitable for the preparation by rccrystallization... 

Acetylfluorene melting at 124-126° has been found to give as good results as the pure compound of melting point 128-129°. The submitters report that the over-all yield from fluorene to fluorenone-2-carboxylic add can be improved by the use of the crude product of the acylation (m.p. 113-117°) without purification (p. 4). 

A solution of 9-diazo-9f/-fluorene (200 mg, 1.0 mmol) in styrene (20 mL, 18.2 g, 0.17 mol) was placed in a Pyrex outer jacket surrounding a quartz immersion well. After being purged with a dry N2 gas stream for 2 h, the solution was irradiated for 24 h with a Hanovia 450-W medium-pressure Hg lamp placed within the water-cooled immersion well and shielded by a cylindrical uranium glass filter to remove all wavelengths below 330 nm. After removal of excess styrene in vacuo, yellow crystals were observed. Purification by chromatography on a column of silica gel (230-400 mesh) with 20% benzene in hexane as eluant gave 246 mg (92%) of product mp 127 C. 

Materials. The preparation, purification, and analyses of 9-phenylflu-orene, fluorene, triphenylmethane, [9-14C]fluorene, triphenyl[14C]methane and [13,14C]H3I have been described previously (2). Tetrabutylammonium hydroxide (Fluka, 1.5 M), n-Bu4NOH, was titrated against standard HCl prior to use. n-Butyllithium (n-BuLi, Aldrich, 1.6 M) was standardized periodically against di-phenylacetic acid according to published procedures (5). Tetrahydrofuran (THF) was freshly distilled from LiAlH4 by using triphenylmethane as an indicator. 

Solid-phase synthesis of the hexamer 106 (Fig. 14) was performed on Rink amide resin by coupling 6>-succinimidyl-(9/7-fluoren-9-ylmethoxycar-bonylamino)-ethyl carbamate derivatives 105b (5 equiv.) with DIEA in DMF for 2 X 90 min. The Fmoc group was removed under standard conditions with 20% piperidine in DMF. After cleavage, the purity of the crude product was about 63% based on HPLC. Lyophilization and HPLC purification yielded 106 in 42% overall yield. Subsequently, it was found that the use of a weaker base such as NMM instead of DIEA led to significant improvement in overall yield (G. Guichard, unpublished data). 

Bis-(4-hydrox5 henyl)-fluorene is commercially synthesized by the reaction of phenol with 9-fluorenone, in the same way as the synthesis of bisphenol A proceeds. Hydrogen chloride, 3-mercaptopropionic acid or methanesulfonic acid are used as catalysts. The condensation reaction of fluorenone and phenol in the presence of gaseous hydrogen chloride proceeds with sufficient speed already by 30°C. ° A high purity monomer can be obtained by a two-step purification process. In the first purification step, the crude 9,9-bis-(4-hydrox5 henyl)-fluorene is refluxed in acetonitrile and recrystallized. In the second step, the product is purified by crystallization from a toluene/isopropanol mixture. 

S. Angiolini and M. Avidano. High purity 9,9-bis-(hydroxyphenyl)-fluorene and method for the preparation and purification thereof. US Patent 6 620 979, assigned to Ferrania, S.p.A. (Ferrania, IT), September 16, 2003. 

In this chapter, synthetic routes to fluorene monomers and fluorene polymerization methods are introduced, with a specific focus on homopolymers. However, the polymerization methods can be used for alternating or random copolymers. Recent developments in polymerization methods, including purification, are mentioned. 

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