O-Halogeno-N-heterocyclics

Salts of o-halogeno-N-heterocyclics, such as 2-fluoro-l-methylpyri-dinium tosylate, and related compounds have been used successfully in a variety of reactions, particularly as agents for esterification, lactoni-zation, and the preparation of amides and thiolic esters They have been used also for the preparation of iodides from alcohols and acid fluorides from the acids as well as for Beckmann rearrangements and reductions, e.g. of a-hydroxyketones to ketones . Various condensed heterocyclic salts have been prepared from l-acylmethyl-2-chloropyridinium salts 2-Dialkylaminopyridinium salts have been used as phase transfer catalysts... 

Without additional reagents o-Amino-o -halogeno-N-heterocyclics from dinitriles... 

The most important families of dyes are azoic and anthraquinonic ones. Azoic dyes are characterised by an azo bond (N=N) connected to aromatic rings or heterocycles, meanwhile anthraquinonic dyes are derivatives of substituted anthraquinone and have two carbonyl groups (C—O) in their structure. Various substitutes can be found, such as alkyl, amino, hydroxy, halogeno, sulphonate or more complex groups. The studied dye solutions have been prepared in water at a concentration of 50 mgL-1. The effect of pH on UV-visible spectra is pointed out. 

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