Recycling of allylic alkylation Pd catalysts containing phosphine-imidazoline ligands in ionic liquids

Fuente, Verónica de la; Fleury‐Brégeot, Nicolas; Castillón, Sergio; Claver, Carmen

doi:10.1039/c2gc35732a

Cited by 18 publications

(5 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This is in contrast to compounds 35 and 39 , which do not possess a hemilabile moiety, and decomposed during column chromatography forming [Pd(allyl)Cl] 2 and a cationic bis‐NHC [Pd(histidylidene) 2 (allyl)] + Cl – complex 41 (Figure 1). Similar complexes have been obtained with noncoordinating counterions 76,77…”

Section: Resultssupporting

confidence: 76%

Allylpalladium(II) Histidylidene Complexes and Their Application in Z‐Selective Transfer Semihydrogenation of Alkynes

et al. 2015

View full text Add to dashboard Cite

We have studied the use of amino acid histidine as a precursor for N-heterocyclic carbene (NHC) ligands. This natural amino acid possesses an imidazole substituent, which makes it an interesting NHC precursor that contains both an acid and an amino functionality. These functionalities may be used for further tuning of NHC complexes. We have developed routes for the synthesis of symmetric and dissymmetric alkyl, benzyl, and aryl-substituted histidinium salts.[a] Molecular Scheme 3. Synthesis of symmetrically substituted benzylic histidinium bromides. The Cyclic Urea ApproachSubsequently, we employed the cyclic urea approach, which allows the synthesis of dissymmetrically substituted histidinium salts and further tuning of the properties of the NHC metal complex. This is not straightforward because histidine has two tautomeric forms, which means that the δ-and the ε-nitrogen of the imidazole possess both imine and amine character (compound 4, Scheme 5). [20] Therefore, mixtures of regioisomers are obtained when the imidazole is reacted with one equivalent of an electrophile. To obtain the desired dissymmetrically substituted histidinium salts, we applied a route based on the report by Hodges and Chivikas, [17] and was improved by Brégeon et al. [30] (Scheme 4). Scheme 4. The cyclic urea route toward dissymmetrically substituted histidinium salts.This cyclic urea route induces regioselectivity because only the six-membered cyclic urea 5 can be formed. The second nitrogen atom can then be functionalized selectively through nucleophilic substitution. Subsequently, the R 1functionalized urea compounds can be ring-opened by reaction with an alcohol, which liberates the δ-nitrogen atom of the imidazole, and provides a carbamate-protected amine. The use of tBuOH affords the Boc-protected histidine, Eur. J. Inorg. Chem. 2015, 982-996

show abstract

Section: Resultssupporting

confidence: 76%

Allylpalladium(II) Histidylidene Complexes and Their Application in Z‐Selective Transfer Semihydrogenation of Alkynes

et al. 2015

View full text Add to dashboard Cite

show abstract

“…2012 年, De la Fuente 等 [71] 有机化学综述与进展应是仿生有机合成化学研究的重要课题 [72] . Pandit 等 [73,74] 曾在 1979 年最早提出以碘化 3-甲基-1-对苯磺酰基(或乙酰基)咪唑啉作为甲酸氧化态的四氢叶酸辅酶模型化合物, 并研究了该模型与各种亲核试剂的反应; 夏炽中等 [75～77] 在此基础上, 进一步做了大量开创性工作, 使咪唑啉模型化合物仿四氢叶酸辅酶生物学功能的合成研究较为系统.…”

Section: 在工业防腐领域的应用unclassified

Progress in the Synthesis and Applications of 2-Imidazolines

Baoyue¹,

Zhang²,

Li³

et al. 2013

Chin. J. Org. Chem.

View full text Add to dashboard Cite

As an important class of heterocyclic scaffolds, 2-imidazolines and their derivatives are an important class of molecules. Based on their good reactivity and biological activity, they are widely used in the field of drugs and pharmaceuticals, natural product chemistry, synthetic organic chemistry, coordination chemistry, anticorrosion and homogeneous catalysis. Significant effort has been devoted to the synthesis and applications of such compounds. This review provides a summary of recently developed methods for the preparation of 2-imidazolines, and their latest developments of applications.

show abstract

“…8 Recently, imidazolium-based ILs were successfully applied in palladium catalysed AAA under MW irradiation to increase the reaction rate, thus avoiding the formation of inactive and non-selective carbenic species, which are otherwise observed. 9 In order to gain insight into the role of palladium species involved in catalysed AAA in imidazolium-based ILs, we assessed the abilities of the catalytic system Pd/(S)-BINAP to perform AAA in a variety of imidazolium-based ILs (Scheme 1). Furthermore, we investigated the species responsible for the activity and selectivity observed.…”

Section: Introductionmentioning

confidence: 99%

Catalyst life in imidazolium-based ionic liquids for palladium-catalysed asymmetric allylic alkylation

Guerrero‐Ríos

Martin

2014

Dalton Trans.

View full text Add to dashboard Cite

A Pd/(S)-BINAP system was successfully applied to the asymmetric allylic alkylation of rac-1,3-diphenyl-3-acetoxyprop-1-ene () using imidazolium-based ionic liquids (ILs) attaining up to 225 h(-1) TOF and 88% ee of the (R)-product. Although the system was barely active in the recycling experiments, the catalyst life was confirmed after recharging the system with substrate/reactants resulting in an alkylated product. In the latter case, the conversion rates and enantiomeric excesses were similar or lower compared to those in the first cycle. In order to explain the observed catalyst performance in the recycling as well as in the recharging experiments, we investigated the reactivity between the catalyst precursors, substrate and reactants in ILs. We were able to identify the species involved in the catalytic reactions under various conditions by means of (31)P NMR analyses. Allylpalladium intermediates () were found to be the active and selective species at a high substrate concentration. When the substrate was consumed, competing reactions took place leading to different palladium complexes. [PdCl(NHC(Bu,Me))((S)-BINAP)]Cl (), together with [Pd((S)-BINAP)2] (), were recognised as the species responsible for the loss of activity, meanwhile, the decrease in enantioselectivity was accounted for by the formation of mixed (NHC)(monophosphine)-palladium species.

show abstract

Recycling of allylic alkylation Pd catalysts containing phosphine-imidazoline ligands in ionic liquids

Cited by 18 publications

References 37 publications

Allylpalladium(II) Histidylidene Complexes and Their Application in Z‐Selective Transfer Semihydrogenation of Alkynes

Allylpalladium(II) Histidylidene Complexes and Their Application in Z‐Selective Transfer Semihydrogenation of Alkynes

Progress in the Synthesis and Applications of 2-Imidazolines

Catalyst life in imidazolium-based ionic liquids for palladium-catalysed asymmetric allylic alkylation

Contact Info

Product

Resources

About