163277-63-2Relevant articles and documents
Catalytic Activation of a Carbon-Chloride Bond by Dicationic Tellurium-Based Chalcogen Bond Donors
Steinke, Tim,Wonner, Patrick,Engelage, Elric,Huber, Stefan M.
, p. 2043 - 2050 (2021)
Noncovalent interactions such as halogen bonding (XB) and chalcogen bonding (ChB) have gained increased interest over the last decade. Whereas XB-based organocatalysis has been studied in some detail by now, intermolecular ChB catalysis only emerged quite
External chiral ligand-induced enantioselective lithiation/S(E)2 reactions of isochroman and phthalan
Tomooka,Wang,Okazaki,Nakai
, p. 6121 - 6125 (2000)
Treatment of isochroman and phthalan with a t-BuLi/chiral bis(oxazoline) complex followed by reaction with carbon-electrophiles such as benzaldehyde and CO2 is shown to afford the α-substituted derivatives in moderate-to-high enantioselectivities (up to 97% ee and 83% ee, respectively). The asymmetric induction is proved to occur at the post-lithiation step. (C) 2000 Elsevier Science Ltd.
Cationic Multidentate Halogen-Bond Donors in Halide Abstraction Organocatalysis: Catalyst Optimization by Preorganization
Jungbauer, Stefan H.,Huber, Stefan M.
, p. 12110 - 12120 (2015)
In contrast to hydrogen bonding, which is firmly established in organocatalysis, there are still very few applications of halogen bonding in this field. Herein, we present the first catalytic application of cationic halogen-bond donors in a halide abstraction reaction. First, halopyridinium-, haloimidazolium-, and halo-1,2,3-triazolium-based catalysts were systematically tested. In contrast to the pyridinium compounds, both the imidazolium and the triazolium salts showed promising potency. For the haloimidazolium-based organocatalysts, we could show that the catalytic activity is based on halogen bonding using, e.g., the chlorinated derivatives as reference compounds. On the basis of these studies, halobenzimidazolium organocatalysts were then investigated. Monodentate compounds featured the same trends as the corresponding imidazolium analogues but showed a stronger catalytic activity. In order to prepare bidentate versions which are preorganized for anion binding, a new class of rigid bis(halobenzimidazolium) compounds was synthesized and structurally characterized. The corresponding syn isomer showed unprecedented catalytic potency and could be used in as low as 0.5 mol % in the benchmark reaction of 1-chloroisochroman with a silyl enol ether. Calculations confirmed that the syn isomer may bind in a bidentate fashion to chloride. The respective anti isomer is less active and binds halides in a monodentate fashion. Kinetic investigations confirmed that the syn isomer led to a 20-fold rate acceleration compared to a neutral tridentate halogen-bond donor. The strength of the preorganized halogen-bond donor seems to approach the limit under the reaction conditions, as decomposition is observed in the presence of chloride in the same solvent at higher temperatures. Calorimetric titrations of the syn isomer with bromide confirmed the strong halogen-bond donor strength of the former (K≈ 4 × 106 M-1, δG≈ 38 kJ/mol).
Stereodivergent Anion Binding Catalysis with Molecular Motors
Dorel, Ruth,Feringa, Ben L.
, p. 785 - 789 (2020)
A photoresponsive chiral catalyst based on an oligotriazole-functionalized unidirectional molecular motor has been developed for stereodivergent anion binding catalysis. The motor function controls the helical chirality of supramolecular assemblies with chloride anions, which by means of chirality transfer enables the enantioselective addition of a silyl ketene acetal nucleophile to oxocarbenium cations. Reversal of stereoselectivity (up to 142 % Δee) was achieved through rotation of the motor core induced by photochemical and thermal isomerization steps.
Anion-Binding Catalysis by Electron-Deficient Pyridinium Cations
Berkessel, Albrecht,Das, Somnath,Pekel, Daniel,Neud?rfl, J?rg-M.
, p. 11660 - 11664 (2014)
A new activation principle in organocatalysis is presented: halide binding through Coulombic interactions. This mode of catalysis was realized by using 3,5-di(carbomethoxy)pyridinium ions that carry an additional electron-withdrawing substituent on the nitrogen atom, for example, pentafluorobenzyl or cyanomethyl. For the N-pentafluorobenzyl derivative, Coulombic interaction with the pyridinium moiety is complemented in the solid state by anion-π interactions with the perfluorophenyl ring. Bromide and chloride are bound by these cations in a 1:1 stoichiometry. Catalysis of the C-C coupling between 1-chloroisochroman (and related electrophiles) with silyl ketene acetals occurs at -78 °C and at low catalyst loading (2 mol %).
Organocatalysis by neutral multidentate halogen-bond donors
Kniep, Florian,Jungbauer, Stefan H.,Zhang, Qi,Walter, Sebastian M.,Schindler, Severin,Schnapperelle, Ingo,Herdtweck, Eberhardt,Huber, Stefan M.
, (2013)
I(n)organocatalysis: Neutral multidentate halogen-bond donors (halogen-based Lewis acids) catalyze the reaction of 1-chloroisochroman with ketene silyl acetals. The organocatalytic activity is linked to the presence (and number as well as orientation) of
Catalytic Carbon–Chlorine Bond Activation by Selenium-Based Chalcogen Bond Donors
Wonner, Patrick,Vogel, Lukas,Kniep, Florian,Huber, Stefan M.
, p. 16972 - 16975 (2017)
Chalcogen bonding is a noncovalent interaction based on electrophilic chalcogen substituents, which shares many similarities with the more well-known hydrogen and halogen bonding. Herein, the first application of selenium-based chalcogen bond donors in or
Preorganization: A Powerful Tool in Intermolecular Halogen Bonding in Solution
Voelkel, Martin H. H.,Wonner, Patrick,Huber, Stefan Matthias
, p. 214 - 224 (2020/03/10)
Preorganization is a powerful tool in supramolecular chemistry which has been utilized successfully in intra- and intermolecular halogen bonding. In previous work, we had developed a bidentate bis(iodobenzimidazolium)-based halogen bond donor which featured a central trifluoromethyl substituent. This compound showed a markedly increased catalytic activity compared to unsubstituted bis(iodoimidazolium)-based Lewis acids, which could be explained either by electronic effects (the electron withdrawal by the fluorinated substituent) or by preorganization (the hindered rotation of the halogen bonding moieties). Herein, we systematically investigate the origin of this increased Lewis acidity via a comparison of the two types of compounds and their respective derivatives with or without the central trifluoromethyl group. Calorimetric measurements of halide complexations indicated that preorganization is the main reason for the higher halogen bonding strength. The performance of the catalysts in a series of benchmark reactions corroborates this finding.
Catalysis with Pnictogen, Chalcogen, and Halogen Bonds
Benz, Sebastian,Poblador-Bahamonde, Amalia I.,Low-Ders, Nicolas,Matile, Stefan
supporting information, p. 5408 - 5412 (2018/03/23)
Halogen- and chalcogen-based σ-hole interactions have recently received increased interest in non-covalent organocatalysis. However, the closely related pnictogen bonds have been neglected. In this study, we introduce conceptually simple, neutral, and mon
Asymmetric Catalysis via Cyclic, Aliphatic Oxocarbenium Ions
Lee, Sunggi,Kaib, Philip S. J.,List, Benjamin
supporting information, p. 2156 - 2159 (2017/02/23)
A direct enantioselective synthesis of substituted oxygen heterocycles from lactol acetates and enolsilanes has been realized using a highly reactive and confined imidodiphosphorimidate (IDPi) catalyst. Various chiral oxygen heterocycles, including tetrahydrofurans, tetrahydropyrans, oxepanes, chromans, and dihydrobenzofurans, were obtained in excellent enantioselectivities by reacting the corresponding lactol acetates with diverse enol silanes. Mechanistic studies suggest the reaction to proceed via a nonstabilized, aliphatic, cyclic oxocarbenium ion intermediate paired with the confined chiral counteranion.
