Benzimidazole 1-alkoxy

Benzimidazole, 2-alkoxy-l-methyl-transalkylation, 5, 443 Benzimidazole, 1-alkyl-metal derivatives, 5, 448 reactions... 

Tab. 12 2-Alkoxycarbonylamino-benzimidazole durch Cyclisierung von o-Diamino-arenen mit Thiokohlensaure-alkoxy-... 

In alkaline solution benzimidazole iodinates at C-2. l-Alkoxy-2-iodobenzimidazole is formed when the corresponding Grignard reagent reacts with iodine. 

The kinetics and mechanism of the transalkylation reaction between 2-alkoxy-1-methyl-benzimidazoles and thiophenol have been studied. The results demonstrate a rapid protonation of the azole followed by an 5n2 reaction which forms the benzimidazolinone. The basicity of the benzimidazole and the pH both affect the reaction rate (Scheme 126). The corresponding sulfur analogue, l-methyl-2-methylthiobenzimidazole, does not react with thiophenol, probably because of the poor electron-donating ability of the sulfur atom of thiophenate (71 JCS(B)2299). 

Some special methods have been developed to prepare benzimidazoles. For example, iV-alkoxy benzimidazoles 1226, 1227 can be prepared in a simple two-step process from 2-fluoro nitroaromatics. The imidazole-forming step involves tandem heterocyclization and 0-alkylation with an in situ alkylating agent (Scheme 305) <2002TL7707>. 

Benzimidazole derivatives with alkoxy groups on adjacent carbon atoms are subject to the o-dialkoxy effect (ODE) (Section III,E,1), The ODE is... 

Replacement of sulphur in 5(6)-alkyl/arylthiobenzimidazole-2-carbamates (50) by oxygen gives 5-alkoxy/aryloxybenzimidazole-2-carbamates (53), which have been found to possess weaker activity than the corresponding 5-alkyl/ arylthiobenzimidazole-2-carbamates [5,85-88], The most effective benzimidazoles of this class are oxibendazole (21) and luxabendazole (22), which exhibit high activity against different helminth parasites in domestic animals [57],... 

Less common methods of synthesis include nitrosation of suitable alkenes in acetonitrile solution (see Section 3.02.8.1.3(ii)) <84TLI319>, cyclization of iV-alkoxy ureas <87S1058>, and specific approaches to benzimidazole oxides from quinoxaline oxides, and to imidazole oxides from oxa-diazine and pyrazine oxides <93CHE127>. 

Miscellaneous PAEs (Table 14). Several other PAEs have been examined with respect to emission. The most interesting ones are PAEs in which pyridine (7). benzimidazole (8) (Table 14. entries 7—9). or bipyridine (9) (Table 14. entry 1) units are separated by alkoxy-substituted diethynylbenzenes or diethynyl-(3-hexylthiophene)s 15. These polymers display high fluorescence, which can be pH dependent. A decrease in pH leads to a bathochromic shift in the emission of the imidazoles 8 and may thus find use in sensory applications. Bipyridine-containing PPE 9 may be useful to detect and connect polymer chains by metal ions in a supramolecular fashion. However, solid-state emission of these materials is mostly not reported. 

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