Konig salts

During the 1950s and 1960s Hafner used Konig salts, derived from the reaction of A -methyl aniline with Zincke salt 1, for azulene synthesis. The Zincke reaction also achieved prominence in cyanine dye synthesis and as an analytical method for nicotinamide determination. ... 

The Zincke reaction is an overall amine exchange process that converts N- 2,A-dinitrophenyl)pyridinium salts (e.g, 1), known as Zincke salts, to iV-aryl or iV-alkyl pyridiniums 2 upon treatment with the appropriate aniline or alkyl amine. The Zincke salts are produced by reaction of pyridine or its derivatives with 2,4-dinitrochlorobenzene. This venerable reaction, first reported in 1904 and independently explored by Konig, proceeds via nucleophilic addition, ring opening, amine exchange, and electrocyclic reclosure, a sequence that also requires a series of proton transfers. By... 

Take for one pound of ore, or what you wish to melt, two pounds granulated lead, five Lot (2l/o oz) salt, five Lot sal alcali, a lye made from willow ashes and quick lime, five Lot corpus mortuus, that is the mud or residue from parting water, five Lot argol (tartar) and heat in a Viennese crucible, and cover it so that nothing unclean may fall into it, and let it fuse in the blast to a regulus (Konig) which then test. ... 

Two modifications of the well-known benzothiazole preparation have been employed to prepare unusual heteropoly cycles. Konig et al.ils treated l-thiocarbamoyl-l,2,3,4-tetrahydroquinoline (236) with bromine in chloroform to give the thiazolo[3,4,5-J,i]quinoline derivative 237. In a process which requires disruption of the resonance stabilization of the pyridine ring, Harris416 reported that treatment of l-(2-pyridyl)-2-thiourcas with sulfuryl chloride or with bromine gives the hydrohalide salts of 2-imino-2//-[l,2,4]thiadiazolo[2,3-a]pyridines (238). 

In 1839, after isolation from Ch. majus, chelerythrine (2) was described by Probst as an alkaloid yielding red salts (from Greek erythros, red) [24,24]. In fact, it was a mixture with sanguinarine [26]. The pure alkaloid was isolated by Konig, who left it the original name, chelerythrine, in spite of the bright yellow colour of its salts [26], The alkaloid toddaline, isolated from Toddalia aculeata Pers. [27], was later proved to be identical with chelerythrine [28,29]. 

Konig s salt. Konig s salt (red), the unsaturated system of which is derived from a pyridine ring, is reduced by NaBH4 in aqueous ethanol at 0° to an enamine which on acid hydrolysis affords pentadienal (R. Grewe ). 

According to Siefken and Konig (323), the addition of heavy metal salts, such as those of lead, facilitates the ring closure. 

Film thickness, um Film appearance Pendulum hardness (Konig), s Adhesion (crosshatch, DIN 53151) Erichsen impact, reverse, mm Conical mandrel bend (ASTM D522-60) Salt-spray resistance (ASTM B117-6U 10 d) 22-28 very good 195 Gt 0 >3 passed 9-9-2 22-28 good 170 Gt 0 >3 passed 85... 

Konigs-Knorr synthesis (1, 1005 4, 67). The Konigs-Knorr synthesis of )3-glucosides is improved with respect to reaction conditions and to yield by use of silver salts of dicarboxylic acids e.g., oxalic acid) or of hydroxy carboxylic acids (e.g., 4-hydroxyvaleric acid). Use of the silver salt of a polymeric reagent offers the further advantages of other polymeric reagents. ... 

Ring fission of pyridinium ions with acceptor substituents, e.g. 7V-2,4-dinitrophenylpyridinium salts 221 (see p 280) leads, on treatment with secondary amines, to pentamethine cyanines 222 (Konig s salts). They condense with sodium cyclopentadienide to yield vinylogous aminofulvenes 223, which on cyclization produce azulene (azulene synthesis according to Ziegler and Hafner, see p 229 [73]) ... 

Systematic investigations were carried out by Adler et al. [39-41] and Konig et al. [26] with various cultivation media. The voliunetric mass transfer coefficients ki,a were determined by a steady state method with distilled water, nutrient salt solution and various cultivation media in the presence and absence of antifoam agents. Volumetric mass transfer coefficients are strongly enhanced by increasing aeration rate. At low superficial gas velocities (< 2.5 cm s ) the... 

Katritzky converted pyrylium salts 44 (formed from the reaction of enone 42 and ethyl pyruvate 43) to the corresponding pyridiniums (45) via ANRORC reaction with a primary amines. This strategy serves as an alternative to the Zincke-Konig method for the formation of substituted pyridinium salts. 

At the turn of the 20 century, Zincke and Konig independently discovered that pyridinium salts could be opened by amines. This process is facilitated by an electron-withdrawing group (commonly 2,4-dinitrophenyl, 53) on the pyridinium nitrogen, and the utilization of sufficiently nucleophilic primary amines can lead to re-cyclization to 55. Overall a net pyridinium A-substituent exchange occurs via an ANRORC process. If secondary amines are utilized, ring closure is prevented, and Zincke aldehydes (54) result. 

Pyridinium ions with acceptor substituents, for example, N-(2,4-dinitrophenyl) pyridinium salts 231 (cf p. 356), are converted to pentamethine cyanines 232 (Konig s salts) by ring-opening with secondary amines. Cyanines 232 condense with Na-cyclopentadienide to yield vinylogous aminofulvenes 233, which on cyclization afford azulene (Ziegler/Hafner azulene synthesis, cf p. 304) [137] ... 

Then in 1925 Konig used N,2-dimethylbenzothiazolium perchlorate (52) for the preparation of methylene base (53, scheme-15) which was used in the synthesis of thiocyanine dyes (Konig Meier 1925). The quaternary salts of benzothiazoles also found recognition in 1928 by Clark (Clark 1928) while studying the absorption sensitivity of the methylene bases from the quaternary salts of 2-methyl benzothiazole. 

Scheme 15. Konig preparation of methylene bases from benzothiazolium salts...

In the same year Konig (Konig 1928) used the quaternary salts of benzothiazole for the preparation of the heterocyclopolymethine dyes during investigations on color and constitution. He claimed that a number of 2-methylbenzothiazoles (56) can be prepared much more conveniently by heating alkaline solutions of 2-aminobenzenethiol (55) with acetic anhydride (54). The benzothiazoles (56) were converted to quaternary salts (57) by reacting with alkyl halides or dimethyl sulfate (scheme-16). 

Like the Zincke reaction, the Konig reaction has been used in synthesizing new quaternary salts 202 for providing the (CH)5 unit for dyestuffs, and for azulene synthesis oa ... 

G. Imperato, E. Eibler, J. Niedermaier, B. Konig, Low-melting sugar-urea-salt mixtures as solvents for Diels-Alder reactions. Chem. Commun. 9, 1170-1172 (2005)... 

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