Efficient novel synthesis of pyrano[3,2-a]- and pyrazolo[4,3-a]-acridines

ABSTRACT

The synthesis of pyrano[3,2-a]acridines is presented, where 7-chloro-9-phenyl-2,3-dihydroacridin-4(1H)-one reacts with arylaldehydes and malononitrile in the presence of piperidine in ethanol, giving with high yield via a multicomponent method. Also a new synthesis of pyrazolo[4,3-a]acridines is reported, where 7-chloro-9-aryl-2,3-dihydroacridin-4(1H)-one on Claisen condensation with ethylformate followed by hydrazine hydrate treatment through the intermediate 7-chloro-4-hydroxy-9-aryl-1,2-dihydroacridin-3-carbaldehyde. The structures of newly synthesized compounds were deduced by spectroscopic techniques, elemental analysis, and single-crystal x-ray diffraction.

GRAPHICAL ABSTRACT

KEYWORDS:

• 7-Chloro-9-aryl-2,3-dihydroacridin-4(1H)-one
• 7-chloro-4-hydroxy-9-aryl-1,2-dihydroacridin-3-carbaldehyde
• multicomponent reaction
• pyrano[3,2-a]acridines
• pyrazolo[4,3-a] acridines

Acknowledgements

Our sincere thanks go to the SIF, VIT-University, Vellore, for providing access to their NMR spectral facilities. W. Kaminsky thanks the Department of Chemistry, University of Washington, Seattle, USA, for free access to the x-ray diffraction facility.