- Polyfluorinated bis-styrylbenzenes as amyloid-β plaque binding ligands
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Detection of cerebral β-amyloid (Aβ) by targeted contrast agents remains of great interest to aid the in vivo diagnosis of Alzheimer's disease (AD). Bis-styrylbenzenes have been previously reported as potential Aβ imaging agents. To further explore their potency as 19F MRI contrast agents we synthetized several novel fluorinated bis-styrylbenzenes and studied their fluorescent properties and amyloid-β binding characteristics. The compounds showed a high affinity for Aβ plaques on murine and human brain sections. Interestingly, competitive binding experiments demonstrated that they bound to a different binding site than chrysamine G. Despite their high logP values, many bis-styrylbenzenes were able to enter the brain and label murine amyloid in vivo. Unfortunately initial post-mortem 19F NMR studies showed that these compounds as yet do not warrant further MRI studies due to the reduction of the 19F signal in the environment of the brain.
- Nabuurs, Rob J.A.,Kapoerchan, Varsha V.,Metaxas, Athanasios,De Jongh, Sanne,De Backer, Maaike,Welling, Mick M.,Jiskoot, Wim,Windhorst, Albert D.,Overkleeft, Hermen S.,Van Buchem, Mark A.,Overhand, Mark,Van Der Weerd, Louise
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supporting information
p. 2469 - 2481
(2014/05/06)
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- Iodonium Cyclophanes for SECURE Arene Functionalization
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This disclosure relates to compounds, reagents, and methods useful in the synthesis of aryl fluorides, for example, in the preparation of 18F labeled radiotracers. For example, this disclosure provides universal “locked” aryl substituents that result in StereoElectronic Control of Unidirectional Reductive Elimination (SECURE) from diaryliodonium salts. The reagents and methods provided herein may be used to access a broad range of compounds, including aromatic compounds, heteroaromatic compounds, amino acids, nucleotides, and synthetic compounds.
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Page/Page column 26
(2011/08/08)
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- Regiospecific reductive elimination from diaryliodonium salts
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(Figure Presented) Out-of-plane steric bulk furnished by a cyclophane substituent on iodine(III) strongly destabilizes the transition state in the reductive elimination from diaryliodonium salts and leads to regiochemical control (dubbed SECURE), as is demonstrated by computational and experimental studies. This approach should be general for high-valent maingroup and transition metal ions. X=N3, OAc, PhO, CF3CH2O, SCN, PhS.
- Wang, Bijia,Graskemper, Joseph W.,Qin, Linlin,DiMagno, Stephen G.
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supporting information; experimental part
p. 4079 - 4083
(2010/08/07)
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- A product analytical study of the thermal and photolytic decomposition of some arenediazonium salts in solution
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Products of thermal and photochemical reactions of eleven arenediazonium tetrafluoroborates in various solvents have been analyzed. All compounds in most solvents undergo unimolecular heterolysis to give singlet aryl cations which are captured by solvent. This mechanism is dominant for arenediazonium ions without electron-withdrawing substituents in all solvents, and the only reaction observed in water. Additionally, appreciable yields of fluoroarenes are obtained by fluoride abstraction by the aryl cation from fluorinated solvents and from tetrafluoroborate in fluorinated solvents. Yields from photochemical processes are very similar to those from thermal reactions indicating that the main reactions proceed through common or very similar intermediates. Aryl cations formed from ion-paired diazonium ions may react with the counterion, but fragmentation of dissociated diazonium ions leads only to solvent-derived product. Some arenediazonium ions in some solvents undergo an alternative radical reaction leading principally to hydrodediazoniation. It is proposed that this reaction involves initial rate-limiting electron transfer from ethanol to the arenediazonium ion followed rapidly by homolysis of the resultant aryldiazenyl radical. Within the same solvent cage, the aryl radical then either abstracts an α-hydrogen from the ethanol radical cation generated in the first step to give the reduction product and protonated acetaldehyde, or combines with it at the oxygen to give a protonated aryl ethyl ether.
- Canning, Peter S. J.,Maskill, Howard,McCrudden, Katharine,Sexton, Brian
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p. 789 - 800
(2007/10/03)
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- Phenyl Cations as Reactive Intermediates in the Solvolysis of Dien-in-yl Triflates
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The synthesis, separation, and solvolysis of the stereoisomeric 1,4-dimethyl-1,3-hexadien-5-yn-1-yl triflates 15a - c in various solvents are described.In contrast to the (Z)-isomers 15a - c, the (E)-isomers 15a - c react preferably via an intermediate phenyl cation 16 to give the phenyl ethers 17.Further mechanistic investigations which support the formation of the intermediate phenyl cations 16 are described.The formation of the benzylic derivatives 18 is discussed.
- Holweger, Walter,Hanack, Michael
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p. 3004 - 3020
(2007/10/02)
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- Experimental Evidence for a Phenyl Cation Intermediate in the Solvolysis Reactions of Dienynyl Trifluoromethanesulphonates
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The synthesis, separation, and solvolysis of the stereoisomeric dienynyl trifluoromethanesulphonates (1) are described, whereby the E-isomers, in contrast with the Z-isomers, rearrange to a remarkable extent to form the phenyl ethers (5) via the phenyl cations (2).
- Hanack, Michael,Holweger, Walter
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p. 713 - 714
(2007/10/02)
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