Synthesis of Glycal-Based Chiral Benzimidazoles by VO(acac)₂−CeCl₃ Combo Catalyst and Their Self-Aggregated Nanostructured Materials

Abstract

VO(acac)(2)-CeCl(3) combo catalyst has been developed for chemoselective cyclocondensation cum oxidation under mild reaction conditions toward synthesis of a new class of optically pure compounds, 2-(2'-C-3',4',6'-tri-O-benzyl/methyl-glycal)-1H-benzimidazoles. It involves an operationally simple synthetic protocol efficient for the syntheses of a wide range of chiral benzimidazoles in high yields without formation of undesired 1,2-disubstituted and pseudoglycal byproducts. Vanadium(V) is found as active oxidant for the chemical processes which is investigated by UV absorption spectroscopy. Highly ordered one-dimensional low molecular mass organic nanostructured materials are fabricated by nanocrystallization of the chiral nanoscale building blocks. Theoretical calculation by the B3LYP/6-31G** level of theory of the glycal-based chiral benzimidazoles shows out of planar geometry of the 1H-anthra[1,2-d]imidazole-6,11-dione moiety, which is responsible for the strong self-aggregation to generate ultralong nanostructured materials. We have also found nice agreement between the theoretical results with the experimental observation in 2D-NOESY experiments. The photophysical property of the solid nanostructured materials is also reported.

Galactosylsphingamides: new α-GalCer analogues to probe the F’-pocket of CD1d

“…4. It was decided to start from commercially available tri- O -acetyl- d -galactal ( 16 ), which was readily converted into the 3,4,6-tri- O -benzyl-protected derivative 17 34 . Hydrolysis of the enol ether was achieved upon treatment with 4 m sulfuric acid, furnishing 2-deoxygalactose intermediate 14 35 .…”

Synthesis and Spectroscopic Analysis of Novel 1H-Benzo[d]imidazoles Phenyl Sulfonylpiperazines

“…Many procedures which can attain this goal have been reported in recent literature. For example, the treatment of the appropriate aldehyde with an ortho- diaminobenzene in the presence of an oxidizing agent can afford the corresponding benzimidazole [16,17,18,19,20]. Also, the treatment of o -nitroanilines with aldehydes in the presence of Na 2 S 2 O 4 can also afford benzimidazoles [21].…”

Metal Catalyzed Synthesis of Pentose-Sugar-Based Chiral 2-Substituted-1H-Benzimidazoles

“…1a,15 However, Maiti and co-workers have established glycal-based chiral benzimidazoles by using Vo(acac) 2 -CeCl 3 Combo catalyst. 16 Cerium is a useful element which have been extensively used in synthetic chemistry. CeCl 3 is a very useful metal catalyst, whose unique behavior is used to synthesis various heterocycle.…”