Benzimidazoles derivatization

Auf ahnliche Weise wird 4-Chlor-2-piperidino-l-nitro-benzol zum Benzimidazol-Derivat cyclisiert4 ... 

Dabei lauft die basenkatalysierte Isomerisierung von 14 zum reak-tiveren A2-Oxazolinon 13 und dessen Aminolyse der Anlagerung des Amins an 14 vollkommen den Rang ab. Das besonders acide 2-Trifluor-methyl-4-(2.2.2-trifluorathyl)-A3-oxazolinon-(5) 188> wird selbst von o-Phenylendiamin isomerisiert, wobei das Benzimidazol-Derivat 53 ent-steht (82> vgl. auch 201>). 

Diformyl-pyrrol598 Zu 24,8 g (0,21 mol) Benzimidazol in 90ml Acetanhydrid gibt man unter Riihren bei 120° tropfenweise die Losung von 6,7 g (0,1 mol) Pyrrol in 10m/ Acetanhydrid. Nach weiteren 3 Stdn. Erhitzen zum Sieden wird gekiihlt und vom Dihydro-benzimidazol-Derivat (44,1 g, 94°/o) abgesaugt. 

Urine extracts from rats exposed to OPD were examined without derivatization. The major metabolites were identified as methyl-benzimidazole, methylquinoxalinc, and dimethylquinoxaline. 

Die wegen dcr Tautomericverhaltnisse (s.S. 219) interessantc Rontgcnstrukturanalyse von 2-Hydroxy-benzimidazol (2-Oxo-2,3-dihydro-benzimidazol) steht bislang nicht zur Verfiigung, 2-Thiono-2,3-dihydro-benzimidazol (2-Merc.apto-benzimidazol) existiert im kristallinen Zustand als planares Thioharnstoff-Derivat mit 80% C,S-Doppelbindungsanteil. Die C,S-Doppel-bindung ist mit 1,672 A etwas kiirzer als in Thioharnstoff selbst (1,71 A)680,s-a-39. 

Bei der Verseifung der 2-Alkoxycarbonyl- bzw. 2-Aminocarbonyl-Funktion decarboxyliert das zunachst entstehende 2-Carboxy-l,3-dimethyl-benzimidazolium-iodidzu 1,3-Dimethyl-benziinid-azoUum-iodid (81% Schmp. 196 -198°). Das Cyan-Derivat solvolysiert allerdings in hoi Bern Methanol zu l,3-Dimethyl-2-oxo-2,3-dihydro-benzimidazol (67%)499 ... 

Eight benzimidazoles Animal tissues ACN extn, liq-liq partns, two SPE cleanups 24 Hewlett-Packard RP-18,5 m, with Kontron RP-18 Presat, 25-40 m, guard column O.OIM pentane-sulfonate contg 0.5% TEA, pH 3.5/ACN (50 50) UV 298 nm/ 20-50 ppb/ GC-NPD 39-87% or GC-EI-MS or GC-Pulsed PICI-NICI-MS after derivatization with methyl iodine or pentafluoro- benzyl bromide 358... 

Multiresidue methods for benzimidazoles and macrocyclic lactones are applied in many testing laboratories. For example, benzimidazoles may be determined by extraction from tissue with ethyl acetate, removal of fat by liquid/liquid partitioning between acidic ethanol and hexane, cleanup by automated SPE on Cl8 or Cg cartridges, and EIPLC chromatography with UV detection at 298 nm. In the case of the macrocyclic lactones, samples are typically extracted using acetonitrile and modified with water-triethylamine prior to purification on Cg or Ci8 SPE cartridges. Residues may be determined, after derivatization, by HPLC with fluorescence detection (excitation 365 nm, emission 475 nm) or determined without derivatization by LC-MS/MS. 

Liquid-liquid extraction (LLE) LLE is the classical method used for herbicide isolation, especially from water and biological fluid samples. Ethyl acetate, dichloromethane, and their mixtures are among the preferred extraction solvents for phenylureas, triazoles, amides, carbamates, benzimidazoles, and chlorotriazines. The extraction efficiency is modified by adjustment of pEI and ionic strength in the aqueous phase. In situ derivatization of the target analytes is also used as an effective tool (e.g., chlorophenoxy acidic herbicides are derivatized with dimethyl sulfate prior to their extraction by n-hexane). The classical way of performing LLE is the separation funnel extraction. Some continuous LLE extractors or steam distillers are also available. 

In the case of biocides giving antibacterial property to the textile material based on nano silver, nano zinc, triclosan, tin organic compounds, benzimidazole derivatives, etc. the limit of detection is 1 ppm for individual substances. The testing method for them is quite complex, requiring derivatization of the same with acetic anhydride, and analysis on capillary GLC with electron capture detection. These antibacterial agents... 

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