Fused Polycyclic Nitrogen-Containing Heterocycles: IX. Oxidative Fusion of Imidazole Ring to 3-Benzoylquinoxalin-2-ones
摘要:
3-alpha-Chlorobenzyl- and 3-benzoylquinoxalin-2-ones react with benzylamine in DMSO to give intermediate 3-(alpha-benzyliminobenzylidene)quinoxalin-2-one which is capable of existing in several tautomeric forms. The subsequent oxidative cyclocondensation leads to imidazo[1,5-a]quinoxalin-4-one. This new procedure for building up iniidazo[1,5-a]quinoxalin-4-one system has been applied to the synthesis of various bis(irnidazo[1,5-a]quinoxalin-4-ones).
4-Aza-2,3-dehydro-4-deoxypodophyllotoxin analogues 3a-n were synthesized through quinolines 2a-n. Comparison of their cytotoxicity against P-388 leukemia cells revealed that the steric effects of the ring B substituents on the activity are greater than the electronic effects, while the presence of a methoxy group on the ring E is not essential to exhibit potent cytotoxicity. Analogues 3a and 3b proved to be more than twice as cytotoxic as natural podophyllotoxin (1). (C) 2000 Elsevier Science Ltd. All rights reserved.