Article (Scientific journals)
Caffeine and theophylline as sustainable, biosourced NHC ligand precursors for efficient palladium-catalyzed Suzuki–Miyaura cross-coupling reactions
Mazars, François; Zaragoza, Guillermo; Delaude, Lionel
2022In Journal of Organometallic Chemistry, 978, p. 122489
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Keywords :
Alkaloids; Biaryls; Carbene ligands; Green chemistry; Palladium; Anion exchange; Complex 1; Green-chemistry; Ligand precursors; Methyl iodide; NHC ligands; Palladium-catalyzed; Suzuki-Miyaura cross-coupling reaction; Biochemistry; Physical and Theoretical Chemistry; Organic Chemistry; Inorganic Chemistry; Materials Chemistry
Abstract :
[en] The alkylation of caffeine with methyl iodide afforded 1,3,7,9-tetramethylxanthinium iodide, which was further reacted with PdCl2, KI, and K2CO3 in neat pyridine to afford the [PdI2(NHC)(Py)] complex 1 in two steps and 73% overall yield. An intermediate anion exchange afforded the corresponding dichlorido complex 2 in 70% overall yield. Theophylline was successfully converted into a new xanthinium salt bearing an isobutyl group on its N7 atom, which was further employed to prepare the [PdCl2(NHC)(Py)] complex 3. These three Pd-PEPPSI catalyst precursors were fully characterized and the molecular structure of complex 2 was determined. Complexes 1–3 displayed a high catalytic activity in the Suzuki–Miyaura cross-coupling of aryl halides with phenylboronic acids. Aryl bromides and iodides bearing either electron-donating or withdrawing substituents afforded a wide range of biaryl derivatives that were isolated in 40–93% yields (30 examples). The reactions required only a low catalyst loading (0.25 mol%) and were carried out in a green, water-based solvent mixture using K2CO3 as a base in the presence of air. Although less reactive, aryl chlorides were also successfully activated under more forcing conditions, provided that an electron-withdrawing group was present on their aromatic ring.
Disciplines :
Chemistry
Author, co-author :
Mazars, François ;  Université de Liège - ULiège > Molecular Systems (MolSys)
Zaragoza, Guillermo;  Universidade de Santiago de Compostela, Santiago de Compostela, Spain
Delaude, Lionel  ;  Université de Liège - ULiège > Département de chimie (sciences) > Chimie organométallique et catalyse homogène
Language :
English
Title :
Caffeine and theophylline as sustainable, biosourced NHC ligand precursors for efficient palladium-catalyzed Suzuki–Miyaura cross-coupling reactions
Publication date :
November 2022
Journal title :
Journal of Organometallic Chemistry
ISSN :
0022-328X
Publisher :
Elsevier B.V.
Volume :
978
Pages :
122489
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 13 September 2022

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