Base‐Regulated Synthesis of the Bestmann‐Ohira or Seyferth‐Gilbert Reagent Utilizing FSO₂N₃

Herein, we present a new application of fluorosulfonylazide (FSO 2 N 3 ) for diazotizing a series of activated methylene compounds to deliver the corresponding diazo products. Notably, by the judicious choice of bases, the selective generation of the Bestmann‐Ohira reagent (BOR) or the Seyferth‐Gilbert reagent (SGR) has been realized from FSO 2 N 3 and dimethyl‐2‐oxopropylphosphonate. We also investigated the kinetics of the homologation of aldehydes using these two reagents with K 2 CO 3 as a base in MeOH, finding that a faster reaction rate was achieved by using SGR. Moreover, the facile one‐pot synthesis of terminal alkynes from aldehydes has been established, which could be further coupled with azides to deliver triazoles using CuAAC click chemistry.