A Facile Method To Transform trans-4-Carboxy-3,4-dihydro-3-phenyl- 1(2H)-isoquinolones to Indeno[1,2-c]isoquinolines

The indeno[1,2-c]isoquinolines are an important class of topoisomerase I inhibitors with anticancer activity. The condensation of Schiff bases with homophthalic anhydrides provides a mixture of cis- and trans-4-carboxy-3,4-dihydro-3-phenyl-1(2H)isoquinolones. Although the cis products can be readily converted to indeno[1,2-c]isoquinolines with thionyl chloride, the trans products do not afford indeno[1,2-c]isoquinolines using this method. The present report describes a route for conversion of the trans diastereomers to indeno[1,2-c]isoquinolines using selenoxide elimination and Friedel−Crafts cyclization chemistry.