Konig reaction

Automation of the manual UV method using an AutoAnalyzer method that incorporates a flash distillation stage has been described [S] and has been used routinely. This technique is unsuitable for unattended automatic operation because the flash distillation stage requires constant supervision. Attention was therefore concentrated on alternative chemical methods of measuring total nicotine alkaloids. By far the most promising of these is an AutoAnalyzer method based on the Konig reaction [6]. The mechanism of this reaction has been discussed by Roy [7] and is illustrated in Fig. 3.S. 

Spectrophotometric determination by use of a modified Konig reaction with NaOCl as the chlorinating agent... 

Derivatization with p-nitrobenzaldehyde followed by reaction with o-dinitrobenzene to yield a purple color LOD = 10 pg/L Barbituric or N,N-dimethylbarbituric acid derivative Spectrophotometric determination by use of a modified Konig reaction with NaOCl as the chlorinating agent... 

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 ... 

Tanaka, A., Deguchi, K., Deguchi, T., 1992. Spectrofluorometric determination of cyanide and thiocyanate based on a modified Konig reaction in a flow-injection system. Anal. Chim. Acta 261, 281—286. 

Cellobiose was prepared first by Skraup and Konig by the saponification of the octaacetate with alcoholic potassium hydroxide, and the method was improved by Pringsheim and Merkatz.3 Aqueous barium hydroxide also has been employed for the purpose, and methyl alcoholic ammonia has been used extensively for the hydrolysis of carbohydrate acetates. The method of catalytic hydrolysis with a small quantity of sodium methylate was introduced by Zemplen,i who considered the action to be due to the addition of the reagent to the ester-carbonyl groups of the sugar acetate and the decomposition of the addition compound by reaction with alcohol. The present procedure, reported by Zemplen, Gerecs, and Hadacsy, is a considerable improvement over the original method (see Note 2). 

This ether, developed for the protection of a pyranoside anomeric hydroxyl, is prepared via a Konigs-Knorr reaction from the glycosyl bromide and 2-(ben-zylthio)ethanol in the presence of DIPEA. It is cleaved, after oxidation with dimethyldioxirane, by treatment with LDA or MeONa. ... 

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... 

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. ... 

This section focuses on the preparation of fluorinated compounds through asymmetric hydrogenation/reduction reactions and nucleophilic additions by listing some examples. The first successful example of catalytic asymmetric hydrogenation of a fluoro-compound was reported by Konig et al.81... 

The syntheses of N-hydroxy-N-nitrosamines are usually carried out by the nitrosation of the corresponding N-hydroxyamines (Scheme 3.8) [123, 124]. N-Hydroxyamines are readily obtained by the reduction of the corresponding nitro-compounds. The most efficient methods are neutral or basic reactions. Recent applications of this method have resulted in the preparation of a variety of cupferron derivatives (Scheme 3.8) via nitrosation of phenylhydroxylamine with amyl nitrite/ammonia [125] or methyl nitrite/ammonia [126]. Behrend and Konig have shown that the organic... 

Fig. 3.5 Schematic representation of mechanism for colour formation in Konig s reaction...

Konig and co-workers also reported that Amberlyst 15 can promote the dehydration of carbohydrates to HMF using safe concentrated low melting mixtures consisting of choline chloride (ChCl) and about 50 wt% of carbohydrates. From fructose, glucose, sucrose, and inulin, HMF was produced with 40, 9, 27, and 54%, respectively within 1 h of reaction at a temperature around 100°C. Montmorillonite has also been used as a solid acid catalyst affording HMF with 49, 7, 35, and 7% yield from fructose, glucose, sucrose, and inulin, respectively [97]. 

The utility of carbodiimide reagents was too important to consider abandoning them. Instead, it rapidly became obvious that carbodiimide activation could be used to prepare in situ active esters. Numerous nucleophilic additives were discovered and prepared for use in these reactions. The most important of these additives was 1,2,3-benzotriazol-l-ol (HOBt, 1), first reported for use in peptide synthesis by Konig and Geiger in 1970.[2(l As an example of a typical result, 1.2 equivalents of HOBt was added to the DCC coupling of Boc-Leu-Phe-OH to H-Val-OtBu in DMF as a solvent. Less than 1% of the l-d-l epimerized tripeptide was formed. When the reaction was carried out in the absence of HOBt, the amount of l-d-l product formed was 14.3%. Addition of HOBt to DCC reactions converts the intermediate G-acylisourea (2) (and any symmetrical anhydride) into the HOBt active ester 3 (Scheme 8). 

Artemov and Shvaika treated a number of 2-aryl-l,3,4-oxadiazole-5(4//)-thiones (293) with methylhydrazine (R = Me) and obtained a mixture of 1-methyl-1,4-dihydro-1,2,4,5-tetrazine-6(5/f)-thiones (294) and 4-methylamino-l,2,4-triazole-3-thiones (295 R = Me) (71KGS905). A similar reaction was reported by Konig and his coworkers, who treated 5-(4-pyridyl)-l,3,4-oxadiazole-2-thione (293 Ar = py) with hydrazine (R = H) and obtained a compound which was either the l,2,4,5-tetrazine-6-thione (294 R = H) or the 4-amino-l,2,4-triazole-3-thione (295 R = H) (54CB825,56GEP953801). 

Blettner, C.G., Konig, W.A., Stenzel, W. and Schotten, T., Microwave-assisted aqueous Suzuki cross-coupling reactions, /. Org. Chem., 1999,64, 3885. 

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