Rolf Koppang

Cellulose fibers from endodontic paper points as an etiological factor in postendodontic periapical granulomas and cysts

Histological sections of eight periapical granulomas and cysts developing after conventional endodontic therapy and displaying faintly hematoxylinophilic, birefringent foreign bodies were investigated by light and polarization microscopy, scanning electron microscopy, energy-dispersive X-ray, and chemical analysis. In addition to a variably dense mononuclear infiltrate, the granulomas and cysts revealed varying amounts of giant cells associated with the birefringent foreign bodies. These structures were identified as cellulose fibers, most probably originating from endodontic paper points, which in our opinion can be held responsible for the initiation and perpetuation of chronic postendodontic periapical lesions.

Substitution on hexafluorobenzene with anilides

The difference in reactivity of lithium anilides towards hexafluorobenzene in different solvents has been described. In tetrahydrofuran lithium N-methylanilide gave a 1,4-disubstituted compound, while lithium anilide rendered a monosubstituted compound. In a mixture of tetrahydrofuran and hexamethylphosphoric triamide lithium N-methylanilide gave a 1,2,4,5-tetrasubstituted compound, while lithium anilide gave a 1,2-disubstituted compound. The anilides have been prepared in tetrahydrofuran at 0–10° by treating the anilines with lithium amide.

Reactions of hexafluorobenzene and pentafluorophenylamino compounds with amides and anilides (steric effects)

Abstract Contrary to N-lithium-N-methylanilide and N-lithium-diphenylamide, trimethyl-N-lithium-N-phenyl-silylamide gave with hexafluorobenzene in molar ratio 2:1, only the monosubstituted compound. Competitive reactions gave the following order of reactivity toward N-lithiumanilide: 2,3,4,5,6-pentafluorotriphenylamine > 2,3,4,5,6-pentafluoro-N-methyl-diphenylamine > hexafluorobenzene ⪢ trimethyl-2,3,4,5,6-pentafluoro-N,N-diphenyl-silylamine. A reason for the low reactivity of trimethyl-2,3,4,5,6-pentafluoro-N,N-diphenyl-silylamine against aromatic amides has been proposed. Some new aromatic amines have been synthesized, among them hexamethyl-N-pentafluorophenyl-disilylamine.

Preparation of poly-(n-phenylimino-perfluoro-phenylene). Solvent effects on reactions between anilides and hexafluorobenzene

Abstract Reactions between anilides and hexafluorobenzene have been shown to be accelerated in presence of dipolar aprotic solvents, and the yield of prepared poly(N-phenylimino-perfluoro-phenylene), from 2,3,4,5,6-pentafluoro-N-lithium-phenylanilide and hexafluorobenzene, reflects this solvent effect. The structure and some thermal properties of the insoluble polymer are discussed.

Synthesis and NMR spectroscopy of 2′, 3′, 4′, 5′, 6′ - pentafluoroformanilide

Abstract Pentafluoroformanilide was prepared by a new synthetical route. The 1 H, 13 C, and 19 F chemical shifts for the compound indicated the presence of cis and trans isomers in chloroform with a rotational energy barrier of 13.4 Kcal mol -1 for the N-C(O) bond. N, N′-Bis(2,3,4,5,6-pentafluorophenyl) formamidine was obtained from pentafluoroformanilide.

Reactions of pentafluorobenzene with amino derivatives.

Abstract A metal hydrogen exchange seems to take place in pentafluorobenzene in reactions with strongly basic amino derivatives, such as lithium amide, lithium morpholide or N-lithium-N′,N′-dimethylhydrazide. On the other hand a fluorine substitution in pentafluorobenzene takes place with N-lithium-p-methoxy-anilide, N-lithium-N-methylanilide, N-1ithiumanilide, dimethylamine, methylamine, ammonia, morpholine, and hydrazine. No reaction occurred with N,N-dimethylhydrazine, p-phenylenediamine, p-methozyaniline, N-methylaniline or aniline.

Reaction of dilfuorocarbene and hexafluoropropene with polyfluorinated N-metal-diphenylamides

Abstract N-difluoromethyl and N-(perfluoropropenyl)-decafluorodiphenylamine together with N-(perfluoropropenyl)-2,3,4,5,6-pentafluorodiphenylamine have been prepared by reacting N-lithium or sodium diphenylamides with difluorocarbene or hexafluoropropene. The amines were hydrolyzed to the respective N,N-decafluorodiphenyl amides with sulphuric acid. The 19 F NMR spectra of the N,N-decafluorodiphenylamides showed a set reasonances for each of the phenyl groups indicating hindered internal rotation around the N-C(O) bond.

β-lumicolchicine as a Tool to Elucidate Microtubular Function in Dentinogenesis

β-lumicolchicine, an isomer of colchicine which does not interrupt microtubular function, was given to 8 rats in a dose of 1.5 mg/kg. Four rats served as controls. Histomorphological investigations of odontoblasts and dentin in the maxillary incisors after two weeks revealed no disturbances. This finding, compared with the previously reported effects of colchicine, as well as colcemid, vincristine and vinblastine, indicates dentin production to be dependant on microtubules.

Disubstitution on hexafluorobenzene with N-methylformamides

Abstract Nucleophilic attack on hexafluorobenzene by N -methylformamide, treated with different bases, gave N -methyl- 2,3,4,5,6-pentafluoroformanilide, N -formyl- N,N′ -dimethyl-2,3,5,6-tetrafluorophenylene- 1,4-diamine and N,N′ -diformyl- N,N′ -dimethyl-2,3,5,6-tetrafluorophenylene-1,4-diamine. The substituted benzenes could be hydrolyzed to N - methyl-2,3,4,5,6-pentafluoroaniline and N,N′ -dimethyl-2,3,5,6-tetrafluorophenylene-1,4-diamine.

Disubstitution on hexafluorobenzene with formanilides

Abstract Nucleophilic attack on hexafluorobenzene by sodium formanilides gave N,N′-diphenyl-2,3,5,6-tetrafluorophenylene-1,4-diamine as the main product at elevated temperature and N,N′-diformyl-N,N′-diphenyl-2,3,5,6-tetrafluorophenylene-1,4-diamine as the main compound at ambient temperature. Metallation of formanilide with lithium hydroxide instead of sodium hydride gave only 2,3,4,5,6-pentafluorodiphenylamine.