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

<p>The synthesis of pyrano[3,2-<i>a</i>]acridines is presented, where 7-chloro-9-phenyl-2,3-dihydroacridin-4(<i>1H</i>)-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-<i>a</i>]acridines is reported, where 7-chloro-9-aryl-2,3-dihydroacridin-4(<i>1H</i>)-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.</p>