2232-08-8Relevant articles and documents
Facile synthesis of β-cyclodextrin-dextran polymers by "click" chemistry
Nielsen, Thorbjorn Terndrup,Wintgens, Veronique,Amiel, Catherine,Wimmer, Reinhard,Larsen, Kim Lambertsen
, p. 1710 - 1715 (2010)
Three series of novel water-soluble β-cyclodextrin-dextran polymers have been prepared by "click" chemistry. The polymers were synthesized from alkyne-modified dextrans (AMDs) onto which mono-6-O-deoxy-monoazido- βCD (N3βCD) was grafted by a copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). The polymers have been characterized by NMR spectroscopy and size exclusion chromatography (SEC). The binding properties have been characterized by isothermal titration calorimetry (ITC) and show excellent accessibility of the βCDs.
Imidazolium-functionalized β-cyclodextrin as a highly recyclable multifunctional ligand in water
Kairouz, Vanessa,Schmitzer, Andreea R.
, p. 3117 - 3124 (2014)
We describe here the synthesis and the catalytic properties of a novel dodecyl-imidazolium modified β-cyclodextrin as a self-assembled catalytic system (Fig. 1) in neat water for an effective Suzuki-Miyaura reaction. The introduction of the dodecyl-imidazolium motif on the primary face of the β-cyclodextrin allowed the development of a green highly recyclable catalytic system for reactions in an aqueous environment. We present the application of this system to the Suzuki-Miyaura coupling without the use of a co-solvent or stabilizing phosphine ligands in aqueous media. The catalytic system is highly recyclable, allowing the reuse of the palladium catalyst in subsequent catalytic runs without loss of activity. This journal is the Partner Organisations 2014.
Reactivity of nucleophiles towards X-3-(p-tolylsulfonyl)-1,2,3-benzoxathiazole 2,2-dioxides: Kinetics, activation volumes and mechanism
Andersen, Kenneth K.,Hubbard, Colin D.,Gerhard, Achim,Van Eldik, Rudi,Kociolek, Marting
, p. 175 - 181 (1997)
The kinetics of the reaction of four X-3-(p-tolylsulfonyl)-1,2,3-benzoxathiazole 2,2-dioxides (X=S-Cl, 5-Br, 5-NO2 and 6-NO2) with hydroxide ion and imidazole in aqueous acetonitrile and aqueous ethanol solutions were investigated at various pressures. The volumes of activation were all found to be negative and consistent with a bimolecular reaction involving considerable solvent electrostriction. No significant dependence on the solvent composition was found.
Lewis acid mediated, mild C-H aminoalkylation of azolesviathree component coupling
Emmert, Marion H.,He, Cyndi Qixin,Shah, Akshay A.,Felten, Stephanie
, p. 3890 - 3897 (2021/04/02)
This manuscript reports the development of a mild, highly functional group tolerant and metal-free C-H aminoalkylation of azolesviaa three-component coupling approach. This method enables the C-H functionalization of diverse azole substrates, such as oxazoles, benzoxazoles, thiazoles, benzothiazoles, imidazoles, and benzimidazoles. DFT calculations identify a key deprotonation equilibrium in the mechanism of the reaction. Using DFT as a predictive tool, the C-H aminoalkylation of initially unreactive substrates (imidazoles/benzimidazoles) can be enabled through anin situprotecting/activating group strategy. The DFT-supported mechanistic pathway proposes key interactions between the azole substrate and the Lewis acid/base pair TBSOTf/EtNiPr2that lead to azole activation by deprotonation, followed by C-C bond formation between a carbene intermediate and an iminium electrophile. Two diverse approaches are demonstrated to explore the amine substrate scope: (i) a DFT-guided predictive analysis of amine components that relates reactivity to distortion of the iminium intermediates in the computed transition state structures; and (ii) a parallel medicinal chemistry workflow enabling synthesis and isolation of several diversified products at the same time. Overall, the presented work enables a metal-free approach to azole C-H functionalizationviaLewis acid mediated azole C-H deprotonation, demonstrating the potential of a readily available, Si-based Lewis acid to mediate new C-C bond formations.
Water soluble homogeneous catalysts that are recoverable by phase selectivity and host-guest interactions
-
Page/Page column 8, (2020/08/30)
A chemical reaction is catalyzed in an organic solvent using a water soluble N-heterocyclic carbene homogeneous catalyst to form a reaction mixture. An aqueous phase in the reaction mixture. A solvent in which the catalyst is insoluble is added to the reaction mixture, causing the catalyst to migrate to the aqueous phase to form a catalyst-laden aqueous phase. The catalyst is extracted from the catalyst-laden aqueous phase.
Electron Transfer Photoredox Catalysis: Development of a Photoactivated Reductive Desulfonylation of an Aza-Heteroaromatic Ring
Qiang-Liu,Liu, Yu-Xiu,Song, Hong-Jian,Wang, Qing-Min
supporting information, p. 3110 - 3115 (2020/07/04)
Herein, we report a protocol for desulfonylation of aza-heteroaromatic rings via photoinduced electron transfer and hydrogen atom transfer. This general protocol has a wide substrate range and moderate to good yields. The utility of the method was demonstrated by the chemoselective desulfonylation of a molecule containing both an aliphatic and an aromatic sulfonamide. (Figure presented.).
Reusable shuttles for exchangeable functional cargos: Reversibly assembled, magnetically powered organocatalysts for asymmetric aldol reactions
Mendoza, Carolina,de la Croix, Augustin,Riente, Paola,Llorens, Lluís,de Mendoza, Javier,Pericàs, Miquel A.
supporting information, (2019/09/17)
A supramolecular approach has been followed to support adamantyl substituted proline organocatalysts onto the surface of magnetite nanoparticles decorated with a β-cyclodextrin motif. The resulting magnetic nanoparticles (ca. ～10 nm diameter) were used as modular, magnetically recyclable catalysts in the asymmetric aldol reaction of aromatic aldehydes with cyclic ketones in water. The catalytic assemblies can be easily dismantled in organic media, and the recovered nanoparticles (magnetically powered chemical shuttles) re-complexed with another suitably substituted catalytic unit (replaceable functional cargo).
Removable Water-Soluble Olefin Metathesis Catalyst via Host-Guest Interaction
Kim, Cheoljae,Ondrusek, Brian A.,Chung, Hoyong
supporting information, p. 736 - 739 (2018/02/09)
A highly removable N-heterocyclic carbene ligand for a transition-metal catalyst in aqueous media via host-guest interactions has been developed. Water-soluble adamantyl tethered ethylene glycol in the ligand leads a hydrophobic inclusion into the cavity of β-cyclodextrin. Ruthenium (Ru) olefin metathesis catalyst with this ligand demonstrated excellent performance in various metathesis reactions in water as well as in CH2Cl2, and removal of residual Ru was performed via filtration utilizing a host-guest interaction and extraction.
Bioactive Phytochemicals: Efficient Synthesis of Optically Active Substituted Flav-3-enes and Flav-3-en-3-o-R Derivatives
Achilonu, Matthew Chilaka,Sedibe, Moosa Mahmood,Shale, Karabo
, (2017/06/05)
The structural core of flavene (2-phenyl-2H-chromene) is commonly found in plant flavonoids, which exhibit a wide range of biological activities and diverse pharmacological profiles (e.g., antioxidant and anticancer activities). Flavonoids have attracted significant interest in medicinal and synthetic chemistry. Substituted flav-3-ene 13 was exclusively synthesized by the stereoselective elimination of the O-mesyl moiety on C-3 of 5,7,3′,4′-tetramethoxyflavan-3-mesylate 12 with 1,8-diazabicyclo[5.4.0]undec-7-ene. The reaction of 5,7,3′,4′-tetramethoxyflavan-3-one 15 with ytterbium trifluoromethanesulfonate in methanol afforded a novel 3-O-substituted flav-3-ene derivative (3,5,7,3′,4′-pentamethoxyflav-3-ene) 17. The reduction of 4-(1,3,5-trihydroxybenzene)-5,7,3′,4′-tetra-O-benzylflavan-3-one 19b with hydrogen afforded a new compound: 3-hydroxy-4-(1,3,5-trihydroxybenzene)-5,7,3′,4′-tetrahydroxyflavan-3-en-3-ol 21 in good yield (95%), while the acetylation of 19a and 21 afforded the expected novel flav-3-en-3-acetoxy derivatives 20 (92%) and 22 (90%), respectively.
Metal-free synthesis of sulfonamides via iodine-catalyzed oxidative coupling of sulfonyl hydrazides and amines
Parumala, Santosh Kumar Reddy,Peddinti, Rama Krishna
supporting information, p. 1232 - 1235 (2016/03/01)
A novel, rapid, and environmentally-friendly protocol for the synthesis of sulfonamides using iodine as catalyst under solvent-free conditions is described. This method involves the oxidative coupling of sulfonyl hydrazides and amines in the presence of catalytic amount of iodine using TBHP as oxidant. This protocol does not require purification techniques such as column chromatography and recrystalization.
