Photocyclisation of 1-styrylimidazoles. A novel route to N-bridgehead compounds

Novel Cyano- and Amidino-Substituted Derivatives of Styryl-2-Benzimidazoles and Benzimidazo[1,2-a]quinolines. Synthesis, Photochemical Synthesis, DNA Binding, and Antitumor Evaluation, Part 3

“…4- N -amidino-substituted 1,2- o -phenylenediamines were prepared from cyano derivatives in the Pinner reaction using earlier described methods. , Cyano-substituted E -2-styryl-1 H -benzimidazoles 24 and 25 were prepared from o -substituted benzaldehydes and 6-cyano-2-methylbenzimidazole . Novel N -amidino-substituted Z -2-styryl-1 H -benzimidazoles 10 − 17 were prepared by photochemical isomerization of ethanolic solution ( c = 1.3 × 10 -2 mol dm -3 ) of N -amidino-substituted E -2-styryl-1 H -benzimidazoles 2 − 9 . Reaction of photochemical isomerization was followed by UV/vis spectroscopy according to the Figure .…”

“…Benzimidazo[1,2- a ]quinolines have remained unexplored for their biological activity most likely because of the lack of general synthetic methods starting from easily accessible precursors. Unsubstituted benzimidazo[1,2- a ]quinoline was first prepared by the classical method from 2-aminoquinoline and picric acid and later also in reaction of photochemical dehydrocyclization by UV irradiation of methanolic solution of styryl-2- benzimidazole . Recently, Venkatesh has developed a new efficient palladium-catalyzed synthetic method for preparing substituted benzimidazo[1,2- a ]quinolines starting from phenylamino-substituted benzimidazoles .…”

Palladium‐Catalyzed Oxidative Intramolecular CC Bond Formation via Double sp2 CH Activation between the 2‐Position of Imidazoles and a Benzene Ring

“…Compared with the cross‐coupling protocols between a CH bond and a CX (X=Cl, Br, I, OTf, CO 2 H) or CM bond (M=B, Sn, Si, Mg, Zn), the oxidative CC bond formation between two CH bonds would be a better choice due to the atom economy and fewer synthetic steps. Early in the 1976, Cooper and Irwin had reported a photocyclization of 1‐styrylimidazoles 12. To the best of our knowledge, no examples of CC bond‐forming cross‐coupling between imidazoles or benzimidazoles and a benzene ring via two CH bonds activation have been documented to form these heteroaromatic structures.…”

Synthesis of Novel Benzimidazolyl-substituted Acrylonitriles and Amidino-substituted Benzimidazo[1,2-a]Quinolines

“…In the photochemical dehydrocyclization reaction of 3 and 4 (ethanolic solution, c = 1.3 × 10 -3 mol dm -3 ) cyclic bezimidazo[1,2-a]quinolines 5 and 6 were prepared [23]. Irradiation was performed for about 12-15 h with a 400-W high-pressure mercury lamp using a Pyrex filter under oxidative conditions, with a small amount of iodine as a catalyst.…”