Synthesis, Characterization, and Catalytic Evaluation of Ruthenium Complexes Bearing Xanthinium-8-dithiocarboxylate Ligands Derived from Caffeine and Theophylline

作者: Delaude, Lionel ; Zaragoza, Guillermo ; Mazars, François

Various exptl. procedures and purification techniques were applied to alkylate or arylate the N7 and N9 positions of caffeine and theophylline into xanthinium salts.These N-heterocyclic carbene (NHC) precursors were converted into xanthinium-8-dithiocarboxylate zwitterions using CS₂ and either Cs₂CO₃ or NaOtBu.The NHC·CS₂ betaines were employed as chelating ligands to prepare a wide variety of [RuX(p-cymene)(S₂C·NHC)]Y (X = Cl, SAc; Y = Cl, PF₆, [RuCl₃(p-cymene)]) and [Ru(S₂C·NHC)₃]X₂ (X = Cl, PF₆) complexes that were characterized by NMR and HRMS.Moreover, the mol. structures of three betaines, one hetero-, and one homoleptic complex were determined by XRD.The catalytic potentials of all these complexes were investigated in the transfer hydrogenation of ketones with isopropanol, the synthesis of vinyl esters from benzoic acid and 1-hexyne, and the cyclopropanation of styrene with Et diazoacetate.The reduction of acetophenone into 1-phenylethanol was chosen as a model reaction for the former application.Monitoring the time course of this transformation showed that chelates bearing a NHC·CS₂ ligand displayed an initial activity slightly higher than the analogous [RuCl₂(p-cymene)(NHC)] complex.Contrastingly, for the last two catalytic processes, the Ru(S₂C·NHC) chelates did not outperform their Ru-NHC counterparts.

2022-11-01·Journal of Organometallic Chemistry

Caffeine and theophylline as sustainable, biosourced NHC ligand precursors for efficient palladium-catalyzed Suzuki–Miyaura cross-coupling reactions

作者: Mazars, Francois ; Delaude, Lionel ; Zaragoza, Guillermo

The alkylation of caffeine with Me 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 iso-Bu 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 mol. structure of complex 2 was determinedComplexes 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.

1998-03-01·Bioorganic & Medicinal Chemistry Letters4区 · 医学

New bronchodilators selected by molecular topology

4区 · 医学

Article

作者: P. Santamaria ; J. Cortijo ; I. Ríos-Santamarina ; J. Gálvez ; R. García-Domenech ; E. Morcillo

Molecular topology has been applied to find new lead compounds with bronchodilator activity. Among the selected compounds stands out 3-(1H-tetrazol-5yl)-9H-thioxanthene-9 -one-10,10-dioxide, anthrarobin, 9-oxo-9H-thioxantene-3-carboxylic-10,10-dioxide acid, acenocoumarol and griseofulvin, with a percentage of relaxation, at 0.1 mM, of 91, 92, 85, 69, and 74%, respectively. Theophylline shows a correspondent value of 77% (Emax = 100% at 1 mM).

100 项与异丁茶碱相关的药物交易

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