BF3.OEt2-promoted synthesis of acridines via N-aryl nitrenium-BF3 ions generated by dissociation of 2-oxo azidoarenes in benzene

Abstract

2-Oxo-substituted aryl azides such as 2-azidobenzenecarbaldehyde 1, 1-(2-azidophenyl)-1-ethanone 2 and (2-azidophenyl) (phenyl)methanone 3 react with benzene in the presence of BF 3 •OEt 2 , mainly affording 9-substituted acridines via formal 2-anilino-oxobenzene-BF 3 complexes rapidly followed by intramolecular cyclo-dehydration at the activated carbonyl groups. Under the same conditions, 2-azidobenzoic acid 4 gives mainly 2-anilinobenzoic acid 4b together with trace amounts of the 9(10H)-acridinone 4a. On the other hand, 2-azidobenzenecarbonitrile 5 gives the 9-amino acridine 5a via a conjugated imine, which undergoes intramolecular cyclization. The BF 3 •OEt 2 promoted dissociation of aryl azides to aryl nitrenium ions is compared with those promoted by AlCl 3 or a strong protic acid (TFA/TFSA mixture).

Synthesis of 5,12-Diazapentacenes and Their Properties

“…The diazapentacenes were obtained from an acid-mediated cyclization of the precursors with trifluoroacetic acid (TFA) and/or trifluoromethanesulfonic acid (TFMSA) using a previous report for the synthesis of 9aminoacridine (9-AA). 22 It is worth noting that the syntheses of the precursors and diazapentacenes proceed in relatively short reaction times with high yields and do not require column chromatography for purification.…”

Synthesis of Acridines by the [4 + 2] Annulation of Arynes and 2-Aminoaryl Ketones

“…Another commonly used method for preparing acridines involves the reduction of acridones . However, until our recent report (eq ), the syntheses of acridones have also required high temperatures and strongly acidic conditions to affect intramolecular electrophilic aromatic substitution of N -phenylanthranilic acids. , Also published recently were the annulations of 2-oxoaryl azides and 2-azidobenzenecarbonitrile by benzene, giving rise to a variety of acridines, including 9-aminoacridine …”