ANTITUMOR POLYCYCLIC ACRIDINES - PART 5 - SYNTHESIS OF 7H-PYRIDO[4,3,2-KL]ACRIDINES WITH EXPLOITABLE FUNCTIONALITY IN THE PYRIDINE RING

Two series of new 9-(1,2,3-triazo-1-yl)acridines 8 and 11 have been sy nthesised by base catalysed cyclisation reaction of 9-azidoacridine 5 with either 1,3-dicarbonyl compounds or activated acetonitriles. Ring formation occurred in a regiospecific manner indicating a stepwise ion ic reaction sequence. The combination of activating base and solvent, as well as the solubility of the products, are crucial for achieving a cceptable yields. Several of the 9-(1,2,3-triazol-1-yl)acridines have been converted to fluorescent 7H-pyrido[4,3,2-kl]acridines 14 by Graeb e-Ullmann nitrogen-expulsion degradations employing boiling diphenyl e ther as the thermolytic medium. In one case, the thermolysis of onyl-5 -(4-chlorobutyl)-1,2,3-triazol-1-yl]acridine 16, the chlorobutyl side- chain participated in an additional intramolecular cyclisation step le ading to the pentacyclic quinolizino[2,3,4-kl]acridine 18.