A photoredox-neutral Smiles rearrangement of 2-aryloxybenzoic acids

Abstract

We report on the use of visible light photoredox catalysis for the radical Smiles rearrangement of 2-aryloxybenzoic acids to obtain aryl salicylates. The method is free of noble metals and operationally simple and the reaction can be run under mild batch or flow conditions. Being a redox neutral process, no stoichiometric oxidants or reductants are needed.

Visible-Light Photoredox-Catalyzed C–O Bond Cleavage of Diaryl Ethers by Acridinium Photocatalysts at Room Temperature

“…S34). These reduction potentials indicate the prior formation of PC -• and the carboxylic acid radical [55][56][57][58][59][60] by a SET between PC* and the carboxylic acid anion. Furthermore, a quantum yield value of φ=0.20 was determined.…”

“…However, the two issues make the transformation more challenging. First, although some intramolecular electrophilic attack of aryl carboxylic acid radicals to arenes has been reported, [55][56][57][58][59][60] the intermolecular electrophilic attack of aryl carboxylic acid radicals to arenes has not been successfully explored. The intermolecular electrophilic attack of aryl carboxylic acid radicals to arenes was proposed in thermal decomposition of substituted dibenzoyl peroxides in diphenyl ether, in which the corresponding aryl benzoates were obtained in less than 39% yields with low selectivity.…”

“…[62][63] However, the possible intermediate B is indicated to lack stronger driving force of C-O bond cleavage, compared with the sixmembered ring intermediate in the intramolecular reaction. [55][56][57][58][59][60] As mentioned below, less than 10% product with the remained starting material was obtained under the optimized reaction conditions for intramolecular reactions (Table 1, entries 1, 2). Perhaps a Lewis acid could activate the ether.…”

Perylene Diimide Based Imine Cages for Inclusion of Aromatic Guest Molecules and Visible‐Light Photocatalysis

“…where F 0 and F are the fluorescent intensity of the emitter and of the mixture of emitter and quencher, respectively, k q is the quenching rate and equals K sv / τ 0 , τ 0 is the lifetime of emitter, and [Q] is the concentration of the quencher . The quenching rate k q of the tested PAHs ranges from 1.8×10 13 L mol −1 s −1 (9,10‐diphenylanthrace) to 7.7×10 13 L mol −1 s −1 (naphthalene) (Scheme S2).…”

“…The results show that the formation of ( RRRR )‐PDI‐TFBE − and the carboxylic acid radical of the substrates is thermodynamically feasible via single‐electron transfer (SET) between ( RRRR )‐PDI‐TFBE* and the carboxylic acid anion of the substrates. Based on the results and the literature, the catalytic mechanism is proposed in Scheme . As indicated, the substituents on the substrate may remarkably change the catalyst‐substrate (host‐guest) interaction, thus causing different catalytic activity.…”