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Its salts are often insoluble in the organic solvent, so precipitation of the pyridinium leaving group complex is an indication of the progress of the reaction. Pyridinium cations are aromatic, as determined through Hückel's rule. [4] They are isoelectronic with benzene.
The formation of the DNP-pyridinium salt. Upon heating a primary amine with the N-2,4-dinitrophenyl-pyridinium salt (2), the addition of the amine leads to the opening of the pyridinium ring. A second addition of amine leads to the displacement of 2,4-dinitroaniline (5) and formation of the König salt [5] (6a and 6b).
In organic synthesis, PPTS is used as a weakly acidic catalyst, providing an organic soluble source of pyridinium (C 5 H 5 NH +) ions.For example, PPTS is used to deprotect silyl ethers or tetrahydropyranyl ethers when a substrate is unstable to stronger acid catalysts.
Pyridinium perbromide (also called pyridinium bromide perbromide, pyridine hydrobromide perbromide, or pyridinium tribromide) is an organic chemical composed of a pyridinium cation and a tribromide anion. It can also be considered as a complex containing pyridinium bromide—the salt of pyridine and hydrogen bromide—with an added bromine (Br ...
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The reaction of pyridine with bromomethyl ketones gives the related pyridinium salt, wherein the methylene group is highly acidic. This species undergoes a Michael-like addition to α,β-unsaturated carbonyls in the presence of ammonium acetate to undergo ring closure and formation of the targeted substituted pyridine as well as pyridinium bromide.
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BEIJING (Reuters) -No one can stop China's "reunification" with Taiwan, Chinese President Xi Jinping said in his New Year's speech on Tuesday, laying down a clear warning to what Beijing regards ...