Oxidative cyclodehydrogenation

Diels-Alder reaction of 22 and cyclopentadienones 24. The second step is an oxidative cyclodehydrogenation to yield HBCs 27. 

Rg. 1. Formation of l,4-bis(benzimidazole-2-yl)benzene by FeCh-catalyzed oxidative cyclodehydrogenation of A,Af -bis(2-aminophenyl)-p-xyIenediimine in dimethylacetamide at 60 °C, monitored by electronic absoiption spectroscopy. Spectra were taken at time intervals over a period of 150 min. Curve 1(5) spectrum taken at start (on completion) of experiment... 

Lewis Acid-Catalyzed Oxidative Cyclodehydrogenation (Scholl Reaction) 377... 

Lewis Acid-Catalyzed Oxidative CYclodehYdrogenation (Scholl Reaction) I 387... 

Under Heck conditions, bromostilbene derivatives 277 reacted with dipheny-lacetylene 278 to afford indene 279. Oxidative cyclodehydrogenation of 279 with FeClj (Scholl reaction) affords the pentalene 280 as a dark purple solid in 38% yield (Scheme 6.70) [164]. Tilley and Levi [165] appUed the method to the synthesis of a series of extended dibenzopentalene derivatives 281-283 (Figure 6.13). 

Scheme 3.3. Synthesis of circumanthracene by photocyclization and oxidative cyclodehydrogenation.

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