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

Herein, we present a new application of fluorosulfonylazide (FSO₂N₃) 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 FSO₂N₃ and dimethyl‐2‐oxopropylphosphonate. We also investigated the kinetics of the homologation of aldehydes using these two reagents with K₂CO₃ 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.