New pathways towards pyridazino-fused ring systems

Novel, efficient synthetic pathways were developed for the synthesis of a variety of pyridazino-fused polycyclic ring systems not easily accessible by other routes. The strategy is based on the sequential or one-pot combinations of a palladium catalyzed C-C bond forming process (Suzuki or Heck-type reaction) and a C-X (X = N, O) or another C-C bond forming reaction (for C-X: nucleophilic substitution, condensation, lactonization, nitrene C-H insertion, Buchwald-Hartwig amination; for C-C: Pschorr reaction, Heck-type reaction). Some of these methodologies have also been extended to the preparation of several diazino-fused ring systems.