Reactions of Arylsulfonate Electrophiles with NMe₄F: Mechanistic Insight, Reactivity, and Scope

Abstract

This paper describes a detailed study of the deoxyfluorination of aryl fluorosulfonates with tetramethylammonium fluoride (NMeF) and ultimately identifies other sulfonate electrophiles that participate in this transformation. F NMR spectroscopic monitoring of the deoxyfluorination of aryl fluorosulfonates revealed the rapid formation of diaryl sulfates under the reaction conditions. These intermediates can proceed to fluorinated products; however, diaryl sulfate derivatives bearing electron-donating substituents react very slowly with NMeF. Based on these findings, aryl triflate and aryl nonaflate derivatives were explored, since these cannot react to form diaryl sulfates. Aryl triflates were found to be particularly effective electrophiles for deoxyfluorination with NMeF, and certain derivatives (i.e., those bearing electron-neutral/donating substituents) afforded higher yields than their aryl fluorosulfonate counterparts. Computational studies implicate a similar mechanism for deoxyfluorination of all the sulfonate electrophiles.

Stereoselective Synthesis of (Z)‐β‐Enamido Triflates and Fluorosulfonates from N‐Fluoroalkylated Triazoles

“…The fluoro-enamides 9 resultedf rom fluorodesulfonylation of 6 and 8.T he formation of 9 is in line with the recent Sandford's reports of nucleophilic deoxyfluorination of aryl triflates and fluorosulfonates in which the latter underwent am ore facile deoxofluorination than triflates. [51,52] Triazoles 1 and 3 were unreactivei nr eactions with other strong acids, such as nitric or chlorosulfonic acids.…”

Deoxyfluorination of (Hetero)aryl Aldehydes Using Tetramethylammonium Fluoride and Perfluorobutanesulfonyl Fluoride or Trifluoromethanesulfonic Anhydride

“…NMe 4 F and 1.2 equiv. PBSF in DMF at room temperature for 24 h. This transformation afforded 1‐bromo‐4‐(difluoromethyl)benzene ( 4 ) in 63 % yield as determined by 19 F NMR spectroscopy (Table , entry 1). Moving to 3 equiv.…”

Sulfonyl Fluorides and Their Analogs Deoxofluorination

“…Mechanistic investigation disclosed that the diaryl sulfates 6 are formed rapidly during the nucleophilic fluorination of aryl fluorosulfonates 4 with NMe 4 F, thus decreasing the efficiency of the fluorination to some extent [16]. The external addition of SO 2 F 2 can suppress the formation of the diaryl sulfates 6 and lead to a productive nucleophilic fluorination reaction via aryl fluorosulfonate intermediates 4.…”

“…The external addition of SO 2 F 2 can suppress the formation of the diaryl sulfates 6 and lead to a productive nucleophilic fluorination reaction via aryl fluorosulfonate intermediates 4. Computational studies suggest that the reaction of aryl fluorosulfonates 4 with fluoride (F À ) proceeds through the formation of a pentacoordinate sulfur species 7 followed by a concerted C-O cleavage and C-F bond formation (Scheme 4) [16].…”