The regio ‐ and chemo ‐selective Pd‐catalyzedC−H activation methods have been successfully reported for directedC−H sulfonation and halogenation of pyridazinedione with arylsulfonyl chlorides and N‐halosuccinimide, respectively. These protocols are compatible with a range of various functional groups on substrates and exhibit excellent regio‐selectivity under mild reaction conditions by use of inexpensive
with α‐diazotized Meldrum’s acid afforded tetracyclic phthalazine derivatives with a carbonyl group in 98% yield in only 30 min. The initial formation of tetracyclic phthalazine derivatives also provided access to a powerful building block. The utility of this method is emphasized by the synthetic transformation into a series of potentially bioactive derivatives.