Benzimidazolones

Chemical Name 1-[3-[4-(Dlphenvlmethyl)-1-piperazlnyl] propyl] -2-benzimidazolone Common Name Oxatimide Structural Formula / ... 

Habib and co-workers observed the rearrangement of 2-quin-oxalinone 4-oxides (219) on treatment with acetic anhydride to 1,3-diacetyl- or l-acetyl-3-acyl-2-benzimidazolones (220).219 Recently, the ring contraction of 2-azidoquinoxaline 1-oxide to 2-cyano-l-hydroxy-benzimidazole has been reported.220... 

Direct-sunlight photolysis of 2-benzoyl-3-phenylquinoxaline 1,4-dioxide (227) yields the ring-contracted product, l,3-dibenzoyl-2-benzimidazolone (228) (70%).53,228... 

Vernin et a/.154 have recently described the synthesis of 1-alkyl- and l,3-dialkyl-2-benzimidazolones from benzimidazolones, using PTC. 

Chemical Name l-[3-[4-(Diphenylmethyl)-l-piperazinyl]propyl]-2-benzimidazolone... 

Ricardo, A.T., Victor, S. and Walter, T. (2003) Electrochemical treatment of industrial wastewater containing 5-amino-6-methyl-2-benzimidazolone. Toward an electrochemical-biological coupling. Water Res. 37,3118-3124. 

When an o-nitroaniline is acylatcd by ethyl chloroformate and then catalyti-cally reduced, thermolysis of the reduction product (33) gives a 1-substituted 2-benzimidazolone (34) (Scheme 2.1.15) f99J. Presumably the carbamates (33) eliminate ethanol as they cyclize. and so the reactions bear similarities to those which proceed through isocyanates (see Scheme 2.1.18). In the presence of magnesium chloride, which appears to activate the urea carbonyl group to solvolysis and condensation, some benzimidazolones are converted into 2-alkyl- and 2-arylbenzimidazoles [100],... 

The difficulty of monobrominating benzimidazole and its 1-substituted derivatives mirrors the state of affairs with the uncondensed imidazoles. Electrophilic bromination occurs at first in the 5-position, then at C-7, but excess brominating agent often substitutes all available positions on the fused benzene ring [23]. It has been found, though, that NBS supported on silica gel forms the 2-bromobenzimidazole (67%) in the first instance [32]. The same compound can also be made from 2-benzimidazolone, and it should be readily available via the 2-anion formed by reaction of an Al-protected benzimidazole with LDA, n-butyllithium or t-butyllithium. Hydroxymethyl and A -(dialkylamino)methyl protecting groups would appear to be the best choices [24, 25]. 

The protonation of a number of nitro-substituted 2-benzimidazolones has been shown to occur on the oxygen, and the usual base-weakening effects of successive nitro groups were observed <83J0U376>. 

Photooxidation of benzimidazole with singlet oxygen in methanol gives 2,4 -bibenzimidazole (10%), 2,5 -bibenzimidazole (22%), 2-benzimidazolone (10%), and the benzimidazo-benzimidazolone (80) (10%) <85CZ231>. 

There are a number of examples also of the formation of 2-imidazolones and 2-benzimidazolones from reaction of 2-halogeno salts with dilute sodium hydroxide <81AG(E)612, 82CHE830>. With... 

Friedel-Crafts acylation of 2-benzimidazolone and its 5-methyl derivative with aliphatic acid chlorides occurs at the 5(6)-positions. It is necessary to use a large excess of aluminum chloride catalyst because it binds at the oxygen function <84CHE658>. 

High yields of 2-imidazolines are obtained on iodocyclization of A-allylthioureas <89TL4435>. Reaction of A-methoxy-A -arylureas with r-butyl hypochlorite gives unstable A-chloro-A-methoxy-A-arylureas which cyclize in basic conditions to give l-methoxy-2-benzimidazolones (56-83%) in a one-pot reaction <82G507>. ) ,y-Acetylenic carbanilides cyclize and subsequently isomerize to 2(3//)-imidazolethiones and 2(3//)-imidazolones when treated with hydrogen sulfide and potassium hydroxide respectively in r-butanol. Yields are almost quantitative <94TL1585>. 

Investigating the photodecomposition of methazole Ivie et al. (1973) found the following photoproducts 3,4-dichloronitrobenzene, l-(3,4-dichlorophenyl)-3-methylurea and two isomer dichloro-l-methyl-2-benzimidazolones. 

Tetrameric caHx[2]benzimidazolone[2]arenes 178a and 178b and octameric calix[4]benzimidazolone[4] arenes 179a-f, have been formed by high dilution and template induced condensation of l,3- > (bromomethyl)benzene and the trinuclear... 

Moriarty and coworkers have developed a convenient synthetic approach to 2-benzimidazolones, 2-benzoxazolones and related compounds based on the Hofmann-type rearrangement in the reaction of anthranilamides, salicylamides and some P-substituted amides with (diacetoxyiodo)benzene [501]. For example, various 2-benzimidazolones (401, X = NR) and 2-benzoxazolones (401, X = O) were prepared by the treatment of amides 400 with (diacetoxyiodo)benzene in a basic methanolic solution (Scheme 3.160). This reaction probably occurs via initial Hofmann-type rearrangement followed by intramolecular cyclization of the intermediate isocyanate [501]. 

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