Photoinduced Tandem Cyclization of Unsaturated Aldehyde Hydrazones with <i>N</i> ‐Amidopyridinium Salts to Access Amidated Pyrazolones

Photopromoted amidation annulation of aldehyde hydrazones with N ‐amidopyridinium salts was completed, which efficiently produced diverse aryl, heterocycle, and alkyl‐featured amidated pyrazolones with good selectivity/substrate scope. Meanwhile, various applied studies (scaled‐up operations and active molecular derivatization transformations) and mechanistic exploration (fluorescence quenching experiments/radical capturation/light‐on–off operations) were performed to test the merits and reaction process of this cascade system.