One-pot synthesis of highly fluorescent polycyclic benzimidazole derivatives

Abstract

An efficient one pot synthesis of polycyclic benzimidazole derivatives has been developed (up to 90% yield). The protocol is very mild, metalfree, and not restricted to anhydrous conditions. It also demonstrates an example of preferential electrocyclic reaction over Michael reaction. These new benzimidazole derivatives are highly fluorescent and show a dramatic change with pH; The characteristic bright bluish fluorescence was observed in MeOH (UV-light, 366 nm) but the intensity was totally diminished at pH ¼ 2.5.

Pd‐catalyzed C‐H Arylation: A General Route for the Synthesis of Benzo[b]carbazolenaphthoquinones

“…Previously our group established a pathway of synthesizing pyranapthoquinones and its related natural product pentalogin via palladium catalyzed Heck reation . In continuation of our endeavor in heterocyclic synthesis , we hereby wish to communicate a synthetic route of benzo[ b ]carbazolenaphthoquinone derivatives 4 by Pd catalyzed C‐H arylation of 2‐bromo‐3‐(arylamino)naphthalene‐1,4‐diones 3 (Scheme ). Moreover, we have developed benzo[ b ]phenazine‐6,11(5H,12H)‐dione derivatives 6 via two component coupling reaction of 2,3‐dibromonaphthalene‐1,4‐dione with o ‐phenelenediamine derivatives in water medium (Scheme ).…”

Polycyclic Benzimidazole: Synthesis and Photophysical Properties

“…The synthesized polycyclic benzimidazoles are highly fluorescent and showed a dramatic change with pH. The characteristic bluish fluorescence was observed in MeOH (UV‐light, 366 nm) but at pH 2.5 the intensity was totally diminished …”