1174062-52-2Relevant academic research and scientific papers
Olefin Metathesis in Confined Geometries: A Biomimetic Approach toward Selective Macrocyclization
Ziegler, Felix,Teske, Johannes,Elser, Iris,Dyballa, Michael,Frey, Wolfgang,Kraus, Hamzeh,Hansen, Niels,Rybka, Julia,Tallarek, Ulrich,Buchmeiser, Michael R.
, p. 19014 - 19022 (2019)
The synthesis of macrocycles is severely impeded by concomitant oligomer formation. Here, we present a biomimetic approach that utilizes spatial confinement to increase macrocyclization selectivity in the ring-closing metathesis of various dienes at elevated substrate concentration up to 25 mM using an olefin metathesis catalyst selectively immobilized inside ordered mesoporous silicas with defined pore diameters. By this approach, the ratio between macro(mono)cyclization (MMC) product and all undesired oligomerization products (O) resulting from acyclic diene metathesis polymerization was increased from 0.55, corresponding to 35% MMC product obtained with the homogeneous catalyst, up to 1.49, corresponding to 60% MMC product. A correlation between the MMC/O ratio and the substrate-to-pore-size ratio was successfully established. Modification of the inner pore surface with dimethoxydimethylsilane allowed fine-tuning the effective pore size and reversing surface polarity, which resulted in a further increase of the MMC/O ratio up to 2.2, corresponding to >68% MMC product. Molecular-level simulations in model pore geometries help to rationalize the complex interplay between spatial confinement, specific (substrate and product) interaction with the pore surface, and diffusive transport. These effects can be synergistically adjusted for optimum selectivity by suitable surface modification.
Multicomponent synthesis of 1,2,3-triazoles in water catalyzed by silica-immobilized NHC-Cu(I)
Wan, Li,Cai, Chun
, p. 1134 - 1140 (2012/10/29)
1,2,3-Triazole derivatives were synthesized in one-pot procedure via three-component reaction between organic halides, aromatic alkynes and sodium azide in the presence of 0.5 mol% Silica-immobilized NHC-Cu(I) catalyst. The catalyst showed high catalytic activity and 1,4-regioselectivity for the [3 + 2] Huisgen cycloaddition in water as a green solvent. This procedure has advantages that without the need to handle organic azides because of they are generated in situ. The reaction has a broad scope and good to excellent yields were obtained. The catalyst was recycled six times without significant loss of activity. Graphical Abstract: 1,2,3-triazole derivatives were synthesized in one-pot procedure via three-component reaction between alkynes, alkyl halides, and sodium azide in the presence of 0.5 mol% Silica-immobilized NHC-Cu(I) catalyst. The catalyst could be readily recovered and reused for 6 cycles without significant loss of its activity[Figure not available: see fulltext.]
Heterogenised N-heterocyclic carbene complexes: Synthesis, characterisation and application for hydroformylation and C-C bond formation reactions
Dastgir, Sarim,Coleman, Karl S.,Green, Malcolm L. H.
, p. 661 - 672 (2011/02/28)
The imidazolium salts: 1-mesityl-3-(3-trimethoxysilylpropyl)imidazolium iodide and 1-tert-butyl-3-(3-trimethoxysilylpropyl)imidazolium iodide, abbreviated as (tmpMes)HI (3a) and (tmptBu)HI (3b), respectively, have been synthesised. The palladium(ii) complexes (η3-C 3H5) (tmpMes)PdCl (5a) and (η3-C 3H5)(tmptBu)PdCl (5b), rhodium(i) and iridium(i) complexes (η4-1,5-COD) (tmpMes)MCl, M = Rh (6a), Ir (7a) and (η4-1,5-COD)(tmptBu)MCl, where M = Rh (6b), Ir (7b), were synthesised by silver transmetallation reactions using the silver(i) complexes (tmpMes)AgI (4a) and (tmptBu)AgI (4b). The iridium complex 7b has been structurally characterised. The Pd(ii) and Rh(i) complexes have been immobilised by attachment to chemically modified MCM-41. The immobilised palladium(ii) materials have been tested as recyclable catalysts for Suzuki type C-C bond formation reactions in water and the immobilised rhodium(i) materials have been examined for their catalytic ability for the hydroformylation of 1-octene.
N′-activation of N-arylimidazoles: Facile syntheses of N-alkyl-N′-arylimidazolium iodides from less expensive chloro substrates
Oertel, Anna Magdalena,Ritleng, Vincent,Chetcuti, Michael J.
experimental part, p. 1647 - 1650 (2009/12/24)
A series of N,N′-asymmetrically substituted imidazolium iodide salts have been synthesized, starting from N-arylimidazoles and the less expensive, but less reactive, 1-chlorobutane or (3-chloropropyl)trimethoxysilane. The addition of potassium iodide and
