Photo‐fluorodecarboxylation of 2‐Aryloxy and 2‐Aryl Carboxylic Acids

Abstract

Coming to light: The title reaction simply requires an aqueous alkaline solution of Selectfluor and light. The method is inexpensive and effective for a wide range of neutral and electron‐poor 2‐aryloxy and 2‐aryl acetic acids to provide fluoromethyl ethers (see scheme) and benzyl fluorides, respectively. The mechanism most likely proceeds through an initial aryl excitation with a subsequent single‐electron transfer.

Recent synthetic additions to the visible light photoredox catalysis toolbox

“…40 Sammis reported a similar transition metal-free photo decarboxylative fluorination of the same class of substrates; however, the reaction required a higher energy UV light source. 41 Later,…”

Decarboxylative Fluorination of Aliphatic Carboxylic Acids via Photoredox Catalysis

“…Indeed, the earlier work of Sammis clearly delineated that such a possibility was viable with an electrophilic source of fluorine. 12 We further assumed that base-mediated formation of an alkyl carboxylate followed by an SET oxidation ( $E_{1/2}^{\text{red}}=+1.16\mathrm{normalV}$ for hexanoate) 16 using the transiently formed Ir(IV) species 5 ( $E_{1/2}^{\text{red}}=+1.69\mathrm{normalV}$ vs SCE in CH 3 CN) 14 would be thermodynamically feasible. This process is envisioned to generate a carboxyl radical, which upon immediate extrusion of CO 2 should provide the SOMO species 7 .…”

“…Precedent for this transformation has been demonstrated via the silver-mediated Hunsdiecker reaction 11 and the work of Sammis to achieve a light-promoted decarboxylative fluorination of 2-aryloxyacetic acids to generate α -oxyfluoro motifs. 12 Despite these seminal studies, a general light-mediated strategy for the fluorination of a wide range of aliphatic carboxylic acids has not yet been reported. In this communication, we further advance the visible light activation concept to describe the first broadly applicable…”

6.06 Synthesis of Fluorides

“…Photodecarboxylative fluorination of α-aryloxyacetic acid with NaOH and F-TEDA-BF 4 can afford aryl fluoromethyl ethers. 46 Additionally, electrochemical fluorination with alkali metal fluorides has been explored as an approach for the synthesis of organofluorides. Propargyl fluorides can be synthesized via deoxyfluorination of propargyl alcohols with DAST 48 and with SF 4 , 49 dialkylaminosulfur trifluorides, 50 Yarovenko's reagent (Figure 1), 51 and Ghosez's reagent (N,N-diisopropyl-1-fluoro-2-methylpropenamine).…”