The Experts below are selected from a list of 114 Experts worldwide ranked by ideXlab platform
Volker Gettwert - One of the best experts on this subject based on the ideXlab platform.
-
Fluorodediazoniation in ionic liquid solvents: new life for the Balz–Schiemann Reaction
Journal of Fluorine Chemistry, 2001Co-Authors: Kenneth K. Laali, Volker GettwertAbstract:Abstract Drawbacks associated with the classic Balz–Schiemann Reaction are eliminated in a series of examples by conducting fluorodediazoniation in ionic liquid solvents, thus opening up a new horizon for a much in demand process.
Marko Anderluh - One of the best experts on this subject based on the ideXlab platform.
-
18 F-Labeled Aryl-Tracers through Direct Introduction of [ 18 F]Fluoride into Electron-Rich Arenes
Current Organic Chemistry, 2013Co-Authors: Mitja Kovac, Sylvie Mavel, Marko AnderluhAbstract:Rapid and efficient methods using no-carried-added [18F]fluoride as the source of fluorine-18 for nucleophilic aromatic fluorination play an important role in the development of new radiopharmaceuticals for positron emission tomography (PET). Molecules that bear electron-rich aromatic moieties are especially difficult to label by direct single-step nucleophilic no-carrier-added radiofluorination. Classical Balz-Schiemann Reaction with its modifications, Wallach Reaction and diaryliodonium salts methodology are a few methods to enable this. The present review provides a critical overview of these chemical methods with the emphasis on diaryliodonium salt as precursors for the direct introduction of [18F]fluoride into electron-rich arenes in synthesis of 18F-labeled molecules for PET scanning.
David M. Perrin - One of the best experts on this subject based on the ideXlab platform.
-
Expanding the Balz–Schiemann Reaction: Organotrifluoroborates Serve as Competent Sources of Fluoride Ion for Fluoro‐Dediazoniation
Chemistry (Weinheim an der Bergstrasse Germany), 2018Co-Authors: Tharwat Mohy El Dine, Omar Sadek, Emmanuel Gras, David M. PerrinAbstract:The Balz-Schiemann Reaction endures as a method for the preparation of (hetero)aryl fluorides yet is eschewed due to the need for harsh conditions or high temperatures along with the need to isolate potentially explosive diazonium salts. In a departure from these conditions, we show that various organotrifluoroborates (RBF3 - s) may serve as fluoride ion sources for solution-phase fluoro-dediazoniation in organic solvents under mild conditions. This methodology was successfully extended to a one-pot process obviating aryl diazonium salt isolation. Sterically hindered (hetero)anilines are fluorinated under unprecedentedly mild conditions in good-to-excellent yields. Taken together, this work expands the repertoire of RBF3 - s to act as fluorine ion sources in an update to the classic Balz-Schiemann Reaction.
-
Expanding the Balz–Schiemann Reaction: Organotrifluoroborates serve as competent sources of fluoride Ion for fluoro-dediazoniation
Chemistry - A European Journal, 2018Co-Authors: Tharwat Mohy el dine, Omar Sadek, Emmanuel Gras, David M. PerrinAbstract:Abstract The Balz–Schiemann Reaction endures as a method for the preparation of (hetero)aryl fluorides yet is eschewed due to the need for harsh conditions or high temperatures along with the need to isolate potentially explosive diazonium salts. In a departure from these conditions, we show that various organotrifluoroborates (RBF3−s) may serve as fluoride ion sources for solution-phase fluoro-dediazoniation in organic solvents under mild conditions. This methodology was successfully extended to a one-pot process obviating aryl diazonium salt isolation. Sterically hindered (hetero)anilines are fluorinated under unprecedentedly mild conditions in good-to-excellent yields. Taken together, this work expands the repertoire of RBF3−s to act as fluorine ion sources in an update to the classic Balz–Schiemann Reaction.
Kenneth K. Laali - One of the best experts on this subject based on the ideXlab platform.
-
Electrophilic chemistry in ionic liquids
2007Co-Authors: Kenneth K. LaaliAbstract:Room temperature ionic liquids (ILs), with low nucleophilicity counterions (OTf, FSO 3 - , PFs 6 - , BF 4 - etc) constitute unique environments for exploring ionic Reactions involving electron-deficient intermediates, in particular carbocations and onium ions. Lewis acids that typically show limited or no solubility in regular organic solvents can in many cases be dissolved/immobilized in imidazolium-based ILs. Moreover, these "designer solvents" appear to be ideal media for utilizing onium salts (i.e. diazonium, selectfluor™ etc) as reagents for synthesis because of their increased solubility in ILs as compared to regular organic solvents (onium salt reagents dissolved in onium salt solvents!). Current interest and activity of this laboratory in the ionic liquids area center around their potential application as solvents and as catalysts in fundamentally important electrophilic transformations, specially those that are carried out on large scale in industry such as nitration, alkylation, acylation and fluorination. The present review summarizes our survey studies in aromatic nitration, aromatic fluorination using NF reagents, fluorodediazoniation (Balz-Schiemann Reaction), trans-acylation and deacylation of aromatic ketones, and in adamantylation of aromatics.
-
Fluorodediazoniation in ionic liquid solvents: new life for the Balz–Schiemann Reaction
Journal of Fluorine Chemistry, 2001Co-Authors: Kenneth K. Laali, Volker GettwertAbstract:Abstract Drawbacks associated with the classic Balz–Schiemann Reaction are eliminated in a series of examples by conducting fluorodediazoniation in ionic liquid solvents, thus opening up a new horizon for a much in demand process.
Omar Sadek - One of the best experts on this subject based on the ideXlab platform.
-
Exploiting boron-fluorine bonds for fluorination and synthesis of potential bi-modal imaging agents
2018Co-Authors: Omar SadekAbstract:The B-F bond has an expansive and rich history in chemical transformations and the versatility of the B-F bond has also shown immense utility in fields as far reaching as Positron Emission Tomography (PET) and fluorescence imaging. The application of B-F bonds for nucleophilic Carbon-Fluorine (C-F) bond formation and the development of novel fluorophores with potential applications in PET/fluorescence bi-modal imaging is reported in this document. Organotrifluoroborates are well known as indispensable synthetic tools for the elaboration of organic molecules. However, the trifluoroborate functionality is generally regarded as an auxiliary group, and its potential as a nucleophilic fluoride (F-) source has remained untested. In this context, the ability of organotrifluoroborates to serve as competent sources of F- was investigated. In an update to the historic Balz-Schiemann Reaction, that traditionally uses BF4- as a source of F-, organotrifluoroborates were shown to mediate the fluorodediazoniation of in situ generated aryl diazonium salts under mild Reaction conditions. In Reactions with an analogous substrate class, unsymmetrical diaryliodonium salts could also be fluorinated using phenyltrifluoroborate via thermal decomposition of the ion pair. Finally, the ability of the trifluoroborate moiety to mediate intramolecular fluorination Reactions was investigated through the synthesis of various trifluoroborate-containing molecular scaffolds. We also investigated novel fluoroborate (B-Fn) complexes of the 2-aryl-benzothiazole scaffold, known for its interaction with Aß aggregates, as fluorescent probes. Three complexes were isolated, characterized and their photophysical properties are reported. A 2,4-diaryl-benzothiazole monofluoroborate complex displaying the most promising photophysical properties, was shown to be stable to aqueous conditions. Fluoride abstraction from this complex was also demonstrated, providing promising preliminary results towards the viability of radiolabelling via 19F-18F isotope exchange. The monofluoroborate complex also showed interesting structural properties given the asymmetric boron centre. Enantiomers of the complex were successfully resolved by chiral chromatography from the racemic mixture, characterized by Circular Dichroism and their stability to inversion investigated.
-
Expanding the Balz–Schiemann Reaction: Organotrifluoroborates Serve as Competent Sources of Fluoride Ion for Fluoro‐Dediazoniation
Chemistry (Weinheim an der Bergstrasse Germany), 2018Co-Authors: Tharwat Mohy El Dine, Omar Sadek, Emmanuel Gras, David M. PerrinAbstract:The Balz-Schiemann Reaction endures as a method for the preparation of (hetero)aryl fluorides yet is eschewed due to the need for harsh conditions or high temperatures along with the need to isolate potentially explosive diazonium salts. In a departure from these conditions, we show that various organotrifluoroborates (RBF3 - s) may serve as fluoride ion sources for solution-phase fluoro-dediazoniation in organic solvents under mild conditions. This methodology was successfully extended to a one-pot process obviating aryl diazonium salt isolation. Sterically hindered (hetero)anilines are fluorinated under unprecedentedly mild conditions in good-to-excellent yields. Taken together, this work expands the repertoire of RBF3 - s to act as fluorine ion sources in an update to the classic Balz-Schiemann Reaction.
-
Expanding the Balz–Schiemann Reaction: Organotrifluoroborates serve as competent sources of fluoride Ion for fluoro-dediazoniation
Chemistry - A European Journal, 2018Co-Authors: Tharwat Mohy el dine, Omar Sadek, Emmanuel Gras, David M. PerrinAbstract:Abstract The Balz–Schiemann Reaction endures as a method for the preparation of (hetero)aryl fluorides yet is eschewed due to the need for harsh conditions or high temperatures along with the need to isolate potentially explosive diazonium salts. In a departure from these conditions, we show that various organotrifluoroborates (RBF3−s) may serve as fluoride ion sources for solution-phase fluoro-dediazoniation in organic solvents under mild conditions. This methodology was successfully extended to a one-pot process obviating aryl diazonium salt isolation. Sterically hindered (hetero)anilines are fluorinated under unprecedentedly mild conditions in good-to-excellent yields. Taken together, this work expands the repertoire of RBF3−s to act as fluorine ion sources in an update to the classic Balz–Schiemann Reaction.
