PPh₃/Selectfluor‐Mediated Transformation of Carboxylic Acids into Acid Anhydrides and Acyl Fluorides and Its Application in Amide and Ester Synthesis

Abstract

By taking the advantage of PPh3/Selectfluor system, carboxylic acids are efficiently converted into the pivotal intermediates acyloxyphosphonium ions that can selectively react with a second carboxylic acid or fluoride to in situ yield the corresponding acid anhydrides or acyl fluorides. The developed protocol features commercially availabile reagents, no involvement of base, room temperature conditions, and simple experimental procedure. Additionally, various amides or esters are readily achieved, respectively, with the addition of amines or alcohols.

Cobalt-Catalyzed Divergent Aminofluorination and Diamination of Styrenes with N-Fluorosulfonamides

“…In addition, it was found that the inclusion of PPh 3 was the major factor in this switch of reactivity from aminofluorination to diamination. Consistent with this observation, mixing of NFSI and PPh 3 readily generated nucleophilic benzenesulfonimide species (PhSO 2 )­N  and fluorine-trapping products (F 2 PPh 3 and FPPh 3 + ; see the Supporting Information for details) …”

N-Hydroxybenzimidazole as a structurally modifiable platform forN-oxyl radicals for direct C–H functionalization reactions

“… 15 , 16 While several synthetic methods for acyl fluorides have been reported, they are typically prepared by using toxic fluorination reagents and/or precious metal catalysts. 17 , 18 Therefore, the development of their different synthetic approach with high practicability is in great demand.…”

Recent Advances in the Synthesis of Acyl Fluorides

“…During the second step, the resulting acyloxyphosphonium Tang and co-workers developed a similar synthetic pathway, by using PPh 3 combined with Selectfluor TM instead of NBS and Et 3 N•3HF (Scheme 28). 46 These conditions provided an anhydride as the major product along with trace amounts of the corresponding acyl fluoride. Even though acyl fluorides could generally not be isolated, small amounts were observed after each reaction.…”