Azetidine Sulfonyl Fluorides (ASFs). For the first time, we report the reactivity of azetidine sulfonyl fluorides (ASF) as reagents for the mild synthesis of 3-aryl-3-substituted azetidines. Reacting PMP(Cbz)ASF 11 with morpholine in acetonitrile in the presence of triethylamine or K2CO3 effected the deFS reaction without any observable SuFEx reactivity (Scheme 4a). The Cbz group was readily removed using TMSI to give NH azetidine-amine 107 in 78% yield, unveiling the additional vector for growth and further derivatization. The NH-amino-azetidines also represent potential isosteres of amidines with differences in conformation, and subtle differences in pKa. The kinetics of the deFS process with PMP OSF (1) and PMP(Cbz)ASF ( ) was examined by heating at 60 °C in MeCN-d3 in the presence of triethylamine and morpholine as a coupling partner. This study revealed a remarkably similar profile for the consumption of these reagents, with only a slightly larger activation energy for the deFS of the azetidine reagent (difference of 2.4 kcal mol -1 ; Scheme 4b).