Cerium(IV) Carboxylate Photocatalyst for Catalytic Radical Formation from Carboxylic Acids: Decarboxylative Oxygenation of Aliphatic Carboxylic Acids and Lactonization of Aromatic Carboxylic Acids

Abstract

We found that in situ generated cerium(IV) carboxylate generated by mixing the precursor Ce(O t Bu) 4 with the corresponding carboxylic acids served as efficient photocatalysts for the direct formation of carboxyl radicals from carboxylic acids under blue light-emitting diodes (blue LEDs) irradiation and air, resulting in catalytic decarboxylative oxygenation of aliphatic carboxylic acids to give C−O bond-forming products such as aldehydes and ketones. Control experiments revealed that hexanuclear Ce(IV) carboxylate clusters initially formed in the reaction mixture and the ligand-to-metal charge transfer nature of the Ce(IV) carboxylate clusters was responsible for the high catalytic performance to transform the carboxylate ligands to the carboxyl radical. In addition, the Ce(IV) carboxylate cluster catalyzed direct lactonization of 2-isopropylbenzoic acid to produce the corresponding peroxy lactone and γ-lactone via intramolecular 1,5-hydrogen atom transfer (1,5-HAT).

Electrophotocatalytic Decarboxylative C−H Functionalization of Heteroarenes

“…Conducting the reaction under air (entry 5) or with the organic catalysts 4b-4e resulted in decreased yields (entries 6-9). Thee lectrophotocatalyticd ecarboxylative alkylation reaction was found to be compatible with primary (7)(8)(9)(10)(11)(12), secondary (13)(14)(15)(16)(17), tertiary (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28), and a-alkoxy (29-32) aliphatic carboxylic acids,d espite the fact that alkyl radicals derived from the latter two were prone to further oxidation (Scheme 2). Furthermore,avariety of N-heterocycles,including several drug molecules,w ere well tolerated.…”

Electrophotocatalytic Decarboxylative C−H Functionalization of Heteroarenes

“…Based on the above studies and previous literature reports, [15,18] ap ossible mechanism for the electrophotocatalytic decarboxylative CÀHalkylation and carbamoylation was proposed using lepidine as amodel substrate.T he alkylation reaction commences with the anodic oxidation of Ce III to Ce IV (Scheme 5d). Thelatter coordinates with the carboxylic acid…”

“…Forschungsartikel under air (entry 5) or with the organic catalysts 4b-4e resulted in decreased yields (entries 6-9). Thee lectrophotocatalyticd ecarboxylative alkylation reaction was found to be compatible with primary (7)(8)(9)(10)(11)(12), secondary (13)(14)(15)(16)(17), tertiary (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28), and a-alkoxy (29-32) aliphatic carboxylic acids,d espite the fact that alkyl radicals derived from the latter two were prone to further oxidation (Scheme 2). Furthermore,avariety of N-heterocycles,including several drug molecules,w ere well tolerated.…”

Nanoarchitectonics for Coordination Asymmetry and Related Chemistry

“…Tsurugi, Satoh, Mashima, and co-workers revealed that formation of an oxygen-bridged hexanuclear Ce cluster has important roles in highly activated photocatalysts. 125 In situ generation of Ce IV carboxylate upon mixing of the precursor Ce(OtBu)4 and the corresponding carboxylic acids worked as efficient photocatalysts to give carboxyl radicals from carboxylic acids with blue light irradiation. Decarboxylative oxygenation of aliphatic carboxylic acids to result in C-O bond products such as aldehydes and ketones was catalytically proceeded.…”