Azahelicenes from the Oxidative Photocyclization of Boron Hydroxamate Complexes.
Chem Asian J
; 12(7): 726-729, 2017 Apr 04.
Article
em En
| MEDLINE
| ID: mdl-28244263
ABSTRACT
Aromatic hydroxamic acids (Ar-CO-NOH-Ar') were used as bidentate chelating ligands to generate the corresponding boron hydroxamate complexes, which were subsequently transformed into nitrogen-containing helicenes (azahelicenes) using an oxidative photocyclization method that is frequently used for stilbene-type (Ar-CH=CH-Ar') precursors of carbohelicenes. The nitrogen atom of the hydroxamate linker was thus directly embedded into the helicene core without using nitrogen-containing aromatic rings in the stilbene-type precursors. In a batch photoreaction, aza[4]helicenes were readily and efficiently prepared, but aza[6]helicenes underwent severe decomposition upon irradiation. Alternatively, a continuous flow photoreactor was employed to furnish an amide-type aza[6]helicene.
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MEDLINE
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En
Ano de publicação:
2017
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Article