The atom-transfer carbonylation reaction of various alkyl iodides thereby leading to carboxylic acid esters was effectively accelerated by the addition of transition-metal catalysts under photoirradiation conditions. By using a combined Pd/hν reaction system, vicinal C-functionalization of alkenes was attained in which α-substituted iodoalkanes, alkenes, carbon monoxide, and alcohols were coupled to give functionalized esters. When alkenyl alcohols were used as acceptor alkenes, three-component coupling reactions, which were accompanied by intramolecular esterification, proceeded to give lactones. Pd-dimer complex [Pd(2)(CNMe)(6)][PF(6)](2), which is known to undergo homolysis under photoirradiation conditions, worked quite well as a catalyst in these three- or four-component coupling reactions. In this metal/radical hybrid system, both Pd radicals and acyl radicals are key players and a stereochemical study confirmed the carbonylation step proceeded through a radical carbonylation mechanism.
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http://dx.doi.org/10.1002/chem.201200752 | DOI Listing |
Angew Chem Int Ed Engl
January 2025
Yunnan University, Key Laboratory of Medicinal Chemistry for Natural Resources, Ministry of Education, East Outer Ring Road, 650500, Kunming, CHINA.
The reduction of carboxylic esters to aldehydes and alcohols is a fundamental functional group transformation in chemistry. However, the inertness of carbonyl group and the instability of ketyl radical anion intermediate impede the reduction of carboxylic esters via photochemical strategy. Herein, we described the reduction of aliphatic carboxylic esters with synergistic dual photocatalysis via phenolate-catalyzed single electron transfer process and thiol-catalyzed hydrogen atom transfer process.
View Article and Find Full Text PDFJ Org Chem
January 2025
College of Material, Chemistry and Chemical Engineering, Key Laboratory of Organosilicon Chemistry and Material Technology, Ministry of Education, Hangzhou Normal University, Hangzhou 311121, China.
In this study, a novel approach that combines photoinduced electron transfer (ET) with hydrogen atom transfer (HAT) has been introduced for the selective β-C(sp)-H pyridination of carbonyl compounds. This method is notable for its absence of transition metals and its ability to function under benign reaction conditions, resulting in a range of pyridinated carbonyl derivatives with consistently moderate to good yields. The significance of this technique is further underscored by its potential for the late-stage functionalization of pharmaceutically significant molecules.
View Article and Find Full Text PDFJ Am Chem Soc
December 2024
Department of Chemistry, University of Wisconsin─Madison, Madison, Wisconsin 53706, United States.
Herein, we introduce a new platform for alkene carboxy-alkylation. This reaction is designed around CO addition to alkenes followed by radical polar crossover, which enables alkylation through carbanion attack on carbonyl electrophiles. We discovered that CO adds to alkenes faster than it reduces carbonyl electrophiles and that this reactivity can be exploited by accessing CO via hydrogen atom transfer from formate.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
November 2024
Univ. Bordeaux, CNRS, Bordeaux INP, ISM UMR 5255, F-33400, Talence, France.
Polystyrene (PS) is a commodity plastic recalcitrant to chemical recycling or upcycling processes. Approaches aimed at deconstructing PS by photocatalytic means struggle to generate high-energy species capable of cleaving the robust C-H and C-C bonds of PS. We show that 9-mesityl-10-methylacridinium perchlorate (MA) is capable of upcycling various grades of PS substrates into up to 40 % benzoic acid (BAc), formic acid (FA) and small proportions of acetophenone (ACP), under visible light (456 nm) or through solar radiation.
View Article and Find Full Text PDFOrg Lett
November 2024
School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China.
A general and flexible platform for catalytic aldehyde-alkyne couplings triggered by ketyl radicals is described. This open-shell strategy necessitates only a catalytic quantity of a photoredox catalyst, along with Hünig's base (DIPEA) as a halogen atom transfer reagent. The reaction proceeds through sequential steps involving activation, halogen atom transfer, and radical addition.
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