Construction of Nitrogen-containing Polycyclic Aromatic Compounds by Intramolecular Oxidative C-H/C-H Coupling of Bis(9H-carbazol-9-yl)benzenes and Their Properties

Synthesis, Structure, and Chiroptical Properties of Indolo‐ and Pyridopyrrolo‐Carbazole‐Based C2‐Symmetric Azahelicenes

“…As for the construction of azahelicenes containing a pyrrole‐type nitrogen, a carbazole skeleton is often employed and typically located in the center of helicene molecules (Scheme 1a, Cz‐helicene), [5g,11a–e] while some related less symmetrical azahelicenes have been known [11f–i] . On the other hand, we have been interested in indolo[3.2.1,‐ jk ]carbazole as another carbazole motif (Scheme 1b, ICz), [12] as the derivatives of ICz are highly fluorescent and can also be appended with donor moieties to form D‐π‐A‐type dyes for applications in dye‐sensitized solar cells [13] and host materials for phosphorescent organic diodes [14] . The ICz skeleton is apparently strained and should be a promising core scaffold of azahelicenes of the twisted nature.…”

“…Consequently, we designed a new ICz‐based azahelicene with C 2 ‐symmetry that contains a pair of ICz units (Scheme 1c, ICz‐helicene). Among two possible key routes for the construction of the ICz‐helicene by means of recently developed step‐economic palladium‐catalyzed dehydrogenative coupling, we chose a double dehydrogenation route of 11,12‐dihydro‐11,12‐diphenyl‐indolo[2,3‐ a ]carbazole, as the similar reaction of 1,2‐di(9 H ‐carbazol‐9‐yl)benzene underwent monocyclization between the carbazole moieties and did not afford the ICz‐helicene structure (Scheme 1d) [12,15] . Herein, we report the successful preparation and optical resolution of diphenyl‐substituted ICz‐helicene and its pyridopyrrolo derivatives, together with their structural, (chir)optical, and electronic features.…”

“…The synthesis of ICz‐helicene 7 (R=H, X=CH) was started from the Ullmann‐type reaction of 11,12‐dihydro‐indolo[2,3‐ a ]carbazole ( 1 a ) with 3‐bromo‐1,1’‐biphenyl ( 2 a ) to give the corresponding 11,12‐bis(1,1’‐biphenyl‐3‐yl)‐substituted indolocarbazole 3 (Scheme 2). [16] Then, this was subjected to double dehydrogenative cyclization with a combination of Pd(TFA) 2 /AgOAc as an oxidant system to furnish the target helicene 7 [12] . The pyridopyrrolo‐type helicene 8 was similarly constructed with use of 1 a and 2‐bromo‐6‐phenylpyridine ( 2 b ) as the starting materials.…”

“…Among two possible key routes for the construction of the ICz-helicene by means of recently developed step-economic palladium-catalyzed dehydrogenative coupling, we chose a double dehydrogenation route of 11, 12-dihydro-11,12-diphenyl-indolo[2,3-a]carbazole, as the similar reaction of 1,2-di(9H-carbazol-9-yl)benzene underwent monocyclization between the carbazole moieties and did not afford the ICz-helicene structure (Scheme 1d). [12,15] Herein, we report the successful preparation and optical resolution of diphenylsubstituted ICz-helicene and its pyridopyrrolo derivatives, together with their structural, (chir)optical, and electronic features. Remarkably, while keeping the comparable structure, chiroptical responses are considerably enhanced in pyridopyrrolo-helicenes as compared with the parent ICz-helicene.…”

Alkylated Indolo[3,2,1-Jk]carbazoles as New Building Blocks for Solution Processable Organic Electronics

“…[11,12,15] Additionally, the planar ICz motif was implemented in larger conjugated systems in electron donating molecules or materials employed as emitters. [30][31][32][33][34] So far, all ICz based materials for OLED devices were exclusively processed by vacuum deposition.…”