Benzimidazolone 5-nitro

Pigment Orange 36 [12236-62-3] 11780 monoaZo benzimid- azolone coupling of diazotized 2-nitro-4-chloro-aniline with acetoacetyl-5-amino-benzimidazolone... 

The effect of a Lewis acid on the o-nitro-(-aniline system is well illustrated by the unexpected result from the attempted Friedel-Crafts acetylation of these compounds. In 1926, van Romburgh and co-workers51,52 observed that the action of acetic anhydride and zinc chloride on the o-nitrodimethylaniline (111) did not give the acetylated product (112), but instead the benzimidazolone (113). Even more surprising was their alleged observation that the same reagents converted the diethyl compound (114) into the quinoxaline... 

Thus, for example, Kym and Ratner [77] found that benzimidazolone (XX) is readily nitrated to the 5,6-dinitro derivative (XXI). According to the experiments of Efros and Yeltsov [78] the compound obtained may undergo further nitration to the tetranitro derivative (XXII) having all nitro groups placed adjacent to one another (see also p. 552) ... 

Figure 8.6. Benzimidazolone reds structure (R = methoxy, Y = nitro for PR 171 X = acetyl, Y = H for PR 175).

Benzimidazolone-2 and benzimidazolthione-2 derivatives are more prone to nitration [105, 106], and in this case the nitro group enters the position 5(6). It should be noted that depending on the reaction conditions, it is possible to obtain benzimidazolone dinitro, trinitro, or tetranitro derivatives [103,107]. 5-Nitrobenzimi-dazolone-2 is nitrated with concentrated nitric acid on heating (80-90°C) only to the position 6 to give 5,6-dinitrobenzimidazolone-2 [108],... 

Analysis of the 13C and 15N NMR spectra of benzimidazolone and its nitro derivatives in comparison with those of model 1,3-dimethyl derivatives has shown nitrobenzimidazolone to exist in the benzimidazolone form A rather than in the... 

The introduction of the nitro group does not affect much the tautomeric equilibrium in the series of benzimidazolones studied. However, the position and number of nitro groups in the compounds influence markedly the values of chemical shifts and coupling constants of 13C and 15N nuclei [562],... 

The tautomerism of nitrated benzimidazolones and benzimidazolethiones is studied [1094,1095]. The vibration frequencies of complexes of 5(6)-nitro- [1096], 4(7)-nitrobenzimidazole [1097] and 5-nitrobenzotriazole [1098] with transition metal ions (Co, Cu, Ni, Zn, Cd, Hg) are reported. The characteristics of infrared spectra of other nitrobenzimidazoles are given in [1099-1101],... 

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>. 

A side-chain methylenamino group reacts with a nitroso group (introduced in situ) when the compound is heated with mineral acid [2466]. An unusual reaction occurred when the nitro-t-amine (103.4) was refluxed with acetic anhydride and zinc chloride the course of this reaction may involve an A -oxide [2039]. When an o-nitroalkylamine is heated with ethoxide, the two functions are converted into a 1-hydroxyimidazole ring [3004]. Nitrosation of the pyrim-idinone (103.5) involves several steps including a Fischer-Hepp rearrangement of an iV-nitroso to a ring-C-nitroso the final product is a 6-(4 -nitrophenyl-amino)purin-2-one [2667]. In a weakly basic medium, the nitroamine (103.6) is cyclized to either the benzimidazole (when R == H), or the benzimidazolone (when R H). 

There are general reviews on heterocyclic syntheses by cycloaddition reactions of isocyanates and on the use of heterocyclic cations in preparative organic chemistry. More specific topics are 5-hydroxymethylfuran-2-carb-aldehyde, isobenzofurans and related ort/io-quinonoid systems, the conversion of 2//-cyclohepta[Zj] furan-2-one (1) into derivatives of azulene, the synthesis of indoles from o-alkylphenyl isocyanides, and abnormal Fischer indolization reactions of o-methoxyphenylhydrazones. Two reviews on isoindoles have appeared and a lecture on highly conducting charge-transfer complexes that are based on heterocyclic selenium and tellurium donors has been reprinted.Recent advances in the chemistry of imidazole and in the use of nitro-imidazoles as radiosensitizers have been summarized. There have been reviews on benzimidazole A -oxides and on dihydrobenzimidazoles, benzimidazolones, benzimidazolethiones, and related compounds. Other topics are synthetic applications of 1,3-dithiolium and 1,3-oxathiolium salts and of isoxazoles, the chemistry of benzisoxazoles, 2-amino-oxazoles, 5-oxazolones (2), furoxans, benzofuroxans, and related systems, the synthesis of five-membered meso-ionic compounds, and tetrazoles. ... 

The synthesis of substituted benzimidazolone analogues (Xi H) was started from appropriate 2-chloronitrobenzenes (VII) as outlined in Scheme 3. The reaction of VII with aminoalkanols in an inert solvent afforded N-hydroxy-alkyl-2-nitroanilines (VIII). Catalytic hydrogenation of the nitro group resulted in o-phenylene-diamines (IX) which reacted with urea to give the N-hydroxyalkyl-benzimidazol-2-ones (X). After treatment of Xwith thionylchlo-ride, the desired chloroalkylbenzimidazol-2-ones (I) could be isolated. 

The behaviour of the two components (aldehyde 24b and nitro compound) separately, in the presence of water and catalyst is shown in runs 7 and 8 respectively. Only a very small amount of aldehyde reacted and the only product observed was the decarbonylated derivative, chlorobenzene. On the contrary, the nitro compound was completely converted, giving mainly o-phenylenediamine (25). Another product formed in significant amounts (30 %) was the benzimidazolone (26) (eq. 11) ... 

Fig. 10. Stepwise transformation of MeO-PEG-bound nitro aniline 11 to MeO-PEG-bound benzimidazolone 14 (top to bottom).

IL-anchored orffeo-phenylenediamine 97 was used as a common scaffold to construct skeletal diversity of novel heterocyclic molecules using various acids, isothiocyanate, and cyanogen bromide (Scheme 12). IL-supported 97 condensation with 3-nitrobenzoic acids followed by cyclization gave benzimidazole heterocycles 100. The ipso-fluoro displacement by primary amine and subsequent nitro reduction resulted benzimidazole-linked o-phenylenediamine 101. IL-grafted 101 was selected as a common scaffold to the synthesis of 2-alkyl-substituted l zs-benzimidazole 102, and pyrrole[l,2-fl]benzimidazolones 103 using various keto acids in one step (Scheme 12) [43]. IL-supported pyrrole[l,2-a]benzimidazolones 103 were treated with Lawesson s reagents to afford thiopyr-ido-benzimidazolone 106. 

---