Acyl Radical Smiles Rearrangement To Construct Hydroxybenzophenones by Photoredox Catalysis

Abstract

The first visible-light-induced acyl radical Smiles rearrangement to transform biaryl ethers to hydroxybenzophenones under mild and metal-free conditions is reported. Using the dual catalysis of hypervalent iodine(III) reagents and organophotocatalysts, ketoacids readily generate acyl radicals and undergo 1,5-ipso addition. This method can construct electron-deficient and electron-rich hydroxybenzophenones with excellent chemoselectivity and on gram scale. The performance of the reaction in neutral aqueous conditions holds potential for future biomolecule applications.

Excited State Anions in Organic Transformations

“…TPT + and ACR + , Figure 2) are strong oxidants in their excited states and have found widespread synthetic applications. [17,[61][62][63][64][65][66][67][68] Surprisingly, in contrast to the wealth of reports dealing with photoexcited cations,t he photochemistry of closed-shell anions has received far less attention, although it constitutes the logical counterpart (Scheme 4E).…”

Recent Synthetic Applications of the Hypervalent Iodine(III) Reagents in Visible-Light-Induced Photoredox Catalysis

“…Chen and coworkers developed the first acyl radical Smiles rearrangement for transformation of biarylethers into hydroxybenzophenones (Li J. et al, 2019 ) ( Figure 12C ). Under dual hypervalent iodine(III)/photoredox catalysis, α-keto acids undergo ester exchange with BI-OAc to form BI-keto acid complexes in situ , which can readily afford acyl radicals and then suffer 1,5-ipso addition and eventually give hydroxybenzophenones.…”

Deoxygenative Arylation of Carboxylic Acids by Aryl Migration

“…2019,25,[12724][12725][12726][12727][12728][12729] www.chemeurj.org by direct deoxygenation of carboxylic acids by means of photoredox catalysis and phosphoranyl radicals ynergism. Twoe legant acyl radical Smiles examples [13] have been reported, but both required the use of external oxidants, such as di-tertbutyl peroxides( DTBP)o rh ypervalent iodine(III) reagents,t o trigger the generation of acyl radicals. Our deoxygenative arylation strategy reflects as ignificant synthetic advance because it is ar edox-neutral process, has mild reaction conditions and uses readily accessible starting materials.…”

“…Startingw ith o-aminobenzophenones, several important five-to eight-membered heterocyclic skeletons can be easily obtained. As shown in Scheme4a, indole (11), quinoline (12), quinazoline (13), diazepinone (14), and dibenzodiazocine (15) can be constructed, furtheru nderscoring the synthetic value of the o-aminobenzophenones. YaequinoloneA2 ( 17), isolated from Penicillium janczewskii or Penicillium sp.…”