Purines,pyrimidines, and related fused systems. 19. Use of S N H methodology for the synthesis of a new heterocyclic system,pyrrolo[3",2":3,4]pyrimido[4,5-c]pyridazine

Sonogashira cross-coupling of 3-chloro-6,8-dimethylpyrimido[4,5-c]pyridazine-5,7(6H,8H)-dione with terminal alkynes afforded the corresponding 3-(alkyn-1-yl) derivatives. Oxidative amination of the latter compounds with primary alkylamines was accompanied by heterocyclization to give 6,8-dimethylpyrrolo[3",2":3,4]pyrimido[4,5-c]pyridazine-7,9(6H,8H)-diones.