Benzimidazole ring

The key synthetic challenges in the target molecule 1 were the chiral 2-arylpyrrolidine fragment, the densely functionalized benzimidazole ring, and the hindered biaryl ether linkage. 

Triazines now are widely used as pesticides. Scheme 107 shows one approach to this class of compounds, which consists in the conversion of the iminophosphorane of 2-aminobenzimidazole (301). After alkylation of the benzimidazole ring, treatment with two equivalents of isothiocyanate affords cyclization to l,3,5-triazino[l,2-a]benzimidazole (302) (92S297). 

JOC4620). The reaction is considered to be initiated by protonation at the nitrogen atom of the benzimidazole ring. The sulfenic acid is eliminated... 

With the aldaric acids, condensation occurs on both ends of the molecule, yielding products having two benzimidazole rings separated by a polyhydroxyalkylidene group, as in 97. These products are well adapted for the characterization of uronic acids and their polymers114-116 and of the hydrolysis products of nucleic acids.117... 

We have previously described the basic resin handling and washing procedures, as well as nitro group reduction, cyclization with aldehydes to form the benzimidazole ring, and chemical encoding procedures for a related benzimidazole system.18 Reagents and solvents used are available from Aldrich (Milwaukee, WI) and Calbiochem-Novabiochem (San Diego, CA). 

The methylsulfinyl group, which adopts a trails conformation, links the pyridine and benzimidazole rings in an almost coplanar orientation. Thus the molecule, as a whole, adopts a nearly extended form. Two centrosymmetrically related molecules form a cyclic dimer by intermolec-ular N-H- O hydrogen bonding, and the dimers are held together by van der Waals contacts between the neighboring aromatic rings in the crystal structure. 

On the other hand, the benzimidazole ring in the dimer also forms a stacking interaction with the centrosymmetrically related ring with an average spacing of 3.38 A (Fig. 4.5B). 

In the synthesis of 47, 4-methoxysalicylaldehyde is condensed with 2-chloro-methyl-l-methyl-5-methylsulfonylbenzimidazole, ring closure is effected, and the product is quatemized with dimethyl sulfate [83], To enhance water solubility, the methyl sulfate anion is converted to the acetate anion the benzimidazole ring is... 

The suspected 5-coordinate complexes, Co(saloph)R and base-off al-kylcobalamins, share the behavior that Co—C bond homolysis is less facile than in the counterpart 6-coordinate complexes, LCo(saloph)R and base-on alkyl-cobalamins [93,141,145], Base-off cobalamins (made by adding acid to hy-dronate the benzimidazole ring) and cobinamides (which are derived from cobalamins but lack 5,6-dimethylbenzimidazole) are believed to be 5-coordinate when R is a strong electron donor, but the evidence is primarily spectroscopic [141], However, 5-coordinate species are generally more thermally stable than their 6-coordinate counterparts. 

The preparation of N-benzyl derivatives by replacement of the acidic hydrogen atom of the benzimidazole ring has been described by Moore and Link20 and by Huebner, Lohmar, Dimler, Moore, and Link.22 Pertinent data on these and other miscellaneous derivatives will be found in Table I of this review. 

Reaction with a pseudo thiourea also leads to the benzimidazole rings... 

The world s best selling medicine in 1998 was Omeprazole, an antiulcer drug from Astra. It prevents excess acid in the stomach and allows the body to heal ulcers. It contains a pyridine ring and a benzimidazole ring, two aromatic heterocycles. 

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