Benzimidazolium

Azomethines add with great ease and stereospecificity to carbon-carbon double bonds affording pyrazolidines. They also add to carbon-carbon triple bonds with the formation of pyrazolines. Benzimidazolium iV-imines, e.g. (622), are a special case of azomethines. Its reaction with DMAD yields l-(2-methylaminophenyl)pyrazole (624), which is formed by cleavage of the initial adduct (623) (75JHC225). 

In situ derived systems, in general, performed similarly to preformed complexes, in telomerisation of butadiene with MeOH, Tables 4.1 and 4.2 [68,70,71,77,78], In situ systans may be generated from free NHC or from imidazolium salt in combination with an appropriate Pd(0) or Pd(ll) source. Typically, 2-4 equivalents of imidazolium salt relative to Pd have been nsed [68,70,77], In situ catalysts derived from mono- and bis-Fc-snbstituted (Fc = ferrocenyl) imidazohnm and benzimidazolium salts (64-68) (Table 4.2) showed interesting telomerisation activities ascribed to the steric bulk of the Fc substituents [70]. Unsymmetrical salts 65 and 66 bearing A -Fc and A -Me... 

The CH groups of those compounds are activated by CN, C02R, Benzimidazolium, or Pyridazine... 

Benzimidazolium is one of the typical scaffolds of the hemicyanine group, and cationic hemicyanine derivatives can be assumed as potential fluorescent sensors due to their electrostatic interactions. Based on this assumption, Chang and... 

Fig. 21 Synthetic scheme of benzimidazolium scaffold-based combinatorial library and their general structures and photophysical properties of the representative examples. All the photophysical properties were measured in methanol...

Wang S, Chang YT (2006) Combinatorial synthesis of benzimidazolium dyes and its diversity directed application toward GTP-selective fluorescent chemosensors. J Am Chem Soc 128 10380-10381... 

Methylsull anyT I //-tetrazole was found to crystallize in a monoclinic form, and could be sublimed into an orthorhombic form, with the structures differing in the relative polarity of the molecular layers in the two forms [47]. /) -1 o d o a ce t o p h e n one was found to crystallize in two polymorphs that both contained C—H-re points of contact, but where the contacts were shorter in one form than in the other [48]. A second monoclinic modification of the mixed salt benzimidazolium 3-carboxyphe-noxyacetate 3-carboxyphenoxyacetic acid was reported, where the acid hydrogen atom and the two monoanions comprised a carboxylate monoanion/neutral molecule in which the acid proton was disordered between the two anionic units [49]. 

Benzimidazolium 1-nitroimidate, 2704 Benzotriazolium 1-nitroimidate, 2281 Benzotriazolium 2-nitroimidate, 2282 4-Nitroamino-1,2,4-triazole, 0777... 

The abnormal metallation is also favored when the conjugated pyridine-imid-azolylidene precursor (with a smaller bite angle) is used. For these precursors, an abnormal binding is produced even with a small wingtip group, as shown in Scheme 3.12. Under the same conditions, the pyridine-benzimidazolium analogue afforded the C2 carbene complex (Scheme 3.12) [27]. 

The abstraction of a hydride is an additional route for the preparation of ben-zimidazolium salts Treatment of 2,3-dihydro-1 /f-benzimidazoles with tritylium tetrafluoroborate generates the benzimidazolium salt and triphenylmethane [Eq. (6)].44... 

The use of /r-hydroxo or ju-alkoxo bridged polynuclear complexes of chromium, molybdenum, tungsten, or rhenium in this route leads to the formation of monomeric bis(NHC) complexes, to the elimination of hydrogen, and to the partial oxidation of the metal [Eq.(ll)]. Chelating and nonchelating imidazolium salts as well as benzimidazolium and tetrazolium salts can be used. 

As mentioned earlier, triazolium salts can be converted into 5-methoxy-4,5-dihydro-lH-triazoles by reacting them with sodium methanolate in methanol. The heterocycles eliminate methanol upon heating in vacuo [Eq. (21)] and the formed triazolin-5-ylidenes can then be isolated. " The same method works with imidazolium and benzimidazolium salts." ... 

Das einfach protonierte Benzimidazolium-tetrafluoroborat( ) liegt dimer vor mit dem Proton in einem asymmetrischen Minimum bei 2,787(3) A zwischen den beiden Ringsystemen678. Die unterschiedlichen N, —C- bzw. C -N-,-Bindungslangen in (2-Naphthyloxy-methyl)-benzimid-azol werden erwartungsgemaB egalisiert, wenn man mit Methyliodid 3-Melhyl-l-(2-naphthyl-oxy-methyl)-benzimidazolium-iodid (II) erzeugt25 (vgl. a. Lit.679). 

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