Carboxy Pyridinium Bromide Perbromide Reagents, Part I: Selective Oxidation of Thiols and Sulfides
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Abstract:
Efficient and convenient oxidation of aliphatic and aromatic thiols to disulfides and of sulfides to sulfoxides with pyridinium hydrobromide perbromide (PHBP), nicotinic acid hydrobromide perbromide (NAHBP), and 2,6-dicarboxy pyridinium hydrobromide perbromide (DCPHBP) in a solvent or under solvent free conditions and at ambient temperature is introduced.Keywords:
Hydrobromide
Pyridinium Compounds
Pyridinium hydrobromide perbromide (PHBP) is a highly efficient reagent for the conversion of 5-substituted-2-alkylidene-4-oxothiazolidine derivatives to the corresponding thiazolidines with two fully delocalized exocyclic double bonds at the C(2) and C(5) positions. This conversion as a two-step bromination-rearrangement process occurs in acetonitrile under homogeneous reaction conditions.
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Pyridinium Compounds
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Abstract The carbon-13 chemical shift of seventeen N-substituted 2,4,6-triphenyl pyridinium salts (TPP) and N-substituted 2,4,6-triaryl pyridinium (TsPP) salts have been determined.
Pyridinium Compounds
Carbon fibers
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Abstract 3,5‐Bis(bromomethyl)pyridine hydrobromide and 3,5‐bis(bromobutyl)pyridine hydrobromide were synthesized from commercially available 3,5‐lutidine. The poly( N‐ alkylation) of these monomers readily yielded new hyperbranched polyelectrolytes. The progress of reaction was followed by 1 H NMR. A second‐order kinetic scheme fits the experimental data. Rate constants and activation parameters were determined, showing the higher reactivity of 3,5‐bis(bromomethyl)pyridine hydrobromide. This was explained by the electron‐attractive effect of pyridinium groups on the CH 2 Br end groups. The structures of the hyperbranched poly[3,5‐bis(alkylene)pyridinium]s were investigated by 1 H and 13 C NMR spectroscopy and a preliminary study of their properties is reported. magnified image
Hydrobromide
Reactivity
Pyridinium Compounds
Proton NMR
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Hydrogen bromide was added to cholesteryl bromide in carbon tetrachloride. In the presence of catechol or ferric chloride a hydrobromide melting at 101.5° was obtained. Addition in ethereal solution gave the same product. Simultaneous action of oxygen yielded another hydrobromide melting at 154° and a substance with the composition of a dibromide of cholesteryl bromide. The direction of addition of hydrogen bromide is assumed to follow the examples of additions to simpler ethenoid compounds. The properties and the transformations of the hydrobromides are described. The both hydrobromides lose hydrogen bromide more or less easily.
Hydrobromide
Hydrogen bromide
Catechol
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Hydrobromide
Thioamide
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Abstract The direct α-thiocyanation of ketones with ammonium thiocyanate has been achieved using pyridinium hydrobromide perbromide under mild and neutral conditions to produce α-ketothiocyanates in excellent yields and with high selectivity.
Hydrobromide
Ammonium thiocyanate
Thiocyanate
Pyridinium Compounds
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Cholesterol appended pyridinium ureas 1 and 2 have been designed and synthesized. The unsymmetrical urea-based chemosensor 1 fluorimetrically distinguishes F− from the other anions examined in both CH3CN and DMSO with appreciable binding constant values. The pyridinium – based symmetrical compound 2 acts as a low molecular weight gelator (LMWG) in CHCl3 and is capable of detecting F− visually by breaking the gel. On the contrary, the chemosensor 1 in DMSO in the presence of tetrabutylammonium fluoride undergoes a change from sol to gel state that produces an unambiguous visual readout of F−.
Pyridinium Compounds
Binding constant
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Efficient and convenient oxidation of aliphatic and aromatic thiols to disulfides and of sulfides to sulfoxides with pyridinium hydrobromide perbromide (PHBP), nicotinic acid hydrobromide perbromide (NAHBP), and 2,6-dicarboxy pyridinium hydrobromide perbromide (DCPHBP) in a solvent or under solvent free conditions and at ambient temperature is introduced.
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Pyridinium Compounds
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The specific conductance of pyridinium , N‐methylpyridinium chloride, N‐methylpyridinium bromide, 4‐methylpyridinium bromide, and pyridinium bromide, was measured as a function of temperature. The NMR spectra of the first three fused salts were also measured over the same temperature ranges. Correlations between conductance data and spectral data were found to exist.
Pyridinium Compounds
Proton NMR
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A novel type of [2+4] capsules based on triple-ion interactions was obtained. Four monovalent anions (bromide, nitrate, acetate, and tosylate) bring together two tetrakis(pyridiniummethyl)tetramethyl cavitands by pyridinium-anion-pyridinium interactions. ESI-MS experiments have confirmed the capsule structure due to different fragmentation pathways of triple ions, cations, and ion-pairs. Each capsule encapsulates one or two anions, depending on its size. The capsules exist in equilibrium with hemicapsules containing three walls. The latter form complexes with phenols and anilines to give new unsymmetrical capsules containing both pyridinium-anion-pyridinium and pyridinium-guest-pyridinium walls.
Pyridinium Compounds
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