Erich Klauke

A new method for the trifluoromethylation of aromatics

Abstract A new method is discribed for introducing a CF3-group, by a single-step synthesis, into aromatic compounds. This trifluoromethylation is done by means of a mixture consisting of HF/CCL4 and the aromatic compound. The reaction is thought to be of a Friedel-Crafts type and limited to aromatics which are not substituted by electron withdrawing groups.

Fluorinated heterocyclic compounds: Selective chlorine/fluorine exchange reactions on pyrimidines

Abstract Selective chlorine/fluorine exchange reactions on tetrachloropyrimidine, 6-methyl-, 6-chloromethyl-, 6-dichloromethyl-, and 6-trichloromethyl-2,4,5-trichloropyrimidine are described. Sodium fluoride, potassium fluoride, hydrogen fluoride, and antimony trifluoride were used as the fluorinating agents. It was found that NaF and KF fluorinate only in the heterocyclic nucleus, HF in the nucleus and in the chlorinated methyl group, and SbF 3 only in the chlorinated methyl group. In the first stage of fluorination with NaF only chlorine bound in position 4 of the pyrimidine ring is exchanged. The HF reaction is an equilibrium reaction in which the substitution of the fluorine for the first chlorine atom occurs preferentially in position 2. The behaviour of partly fluorinated pyrimidines in nucleophilic exchange reactions is also discussed.

A new route to the synthesis of 5-fluorouracil

Abstract Starting from tetrafluoropyrimidine (1), selective fluorine/ chlorine exchange reactions and selective hydrogenolysis of the chlorine substituents are described. Combination of these methods, together with a subsequent hydrolysis reaction, provides a new route to the synthesis of 5-fluorouracil via 4,6-dichloro-2,5-difluoropyrimidine and 4-chloro-2,5-difluoropyrimidine.

Reactions in anhydrous hydrogen fluoride

Abstract Anhydrous hydrogen fluoride serves as an excellent agent for introducing fluorine into organic compounds, as a solvent and a catalyst with Friedel-Crafts activity. A number of chlorine/fluorine exchange reactions which occur in HF are described, some of which have involved surprising rearrangement processes. New reactions, in which the catalytic action of hydrogen fluoride are utilized, are also discussed.

Fluoronated heterocyclic compounds: Selective chlorine/fluorine exchange reactions on pyridazines

Abstract This work describes selective chlorine/fluorine substitution reactions on tetrachloropyridazine. Sodium fluoride, potassium fluoride and hydrogen fluoride were used as the fluorinating agents. It was found that sodium fluoride and potassium fluoride in the first fluorinating stage produce an exclusive substitution by fluorine of the chlorine bound in the 3-position. Difluorination and trifluorination produce mixtures of the three possible difluorinated pyridazines and the two possible trifluorinated pyridazines. The hydrogen fluoride reaction is an equilibrium reaction in which the substitution of the first chlorine for fluorine also occurs exclusively in the 3-position. Double chlorine/fluorine substitution only gives 3,6-difluoro-4,5-dichloropyridazine, triple substitution only producing 3,4,6-trifluoro-5-chloropyridazine.

Reduktion von benzotrichloriden zu benzalchloriden

Abstract Benzal chlorides are prepared from the corresponding benzotrichlorides by reduction with thiophenol in the presence of catalytic amounts of copper(I) bromide.

A new method for the trifluoromethylation of aromatic compounds

Abstract Trifluoromethyl groups attached to aromatic compounds are usually prepared by perchlorinating a methyl group and is subsequently perfluorinated by halogen exchange using a fluorinating agent. In addition to this method, which is also used in industry, there are also a number of different synthesis methods which are however only of limited importance owing to the costly reagents required. The disadvantage of the above-mentioned two-step synthesis lies in the restricted range of application since many of the substituents attached to the aromatic compound hinder the chlorination of the methyl group or they are themselves changed (e. g. methyl, bromine …). By means of a new one-step process, the trifluoromethylation of aromatic compounds is made possible by using the reagent HF/CCl4. RH, alkyl, aryl, halogen, phenoxy The anhydrous hydrofluoric acid acts as a Friedel-Crafts-catalyst, solvent and fluorinating agent. The fange of application of the reaction is discussed. Apart from indicating the influence of the concentration of the reaction components, temperature and pressure, details are also given concerning catalysts and side reactions.

Azomethine I: Fluorierung von Tetrachloräthan-1, 2-bisisocyanid-dichlorid☆

Zusammenfassung Die Fluorierung von Tetrachlorathan-1,2-bisisocyanid-dichlorid (I) 1 mit NaF in Sulfolan wurde untersucht. Ein Reaktionsschema zur Deutung der entstehenden Produkte wird diskutiert.

Eine ungewöhnliche Cl-F-Austauschreaktion bei Halogenalkylthioetherketonen

Abstract The syntheses of ∝ - sulfinated compounds are described. Their reactions with HF are investigated. A Cl/F-exchange reaction with a spontaneous rearrangement into a β-fluorinated thioethercarbonylfluoride was observed. Factors influencing the reaction and the mechanism are discussed.

Reactions involving fluoride ion. Part 33 [1]. Perfluoroaza-alkylation of fluorinated heteroaromatics with perfluoro-1-methyl-1,3-diazacyclopent-2-and -3-ene

Abstract The nitrogen anion (1), generated by reaction of fluoride ion with (2), can be trapped by fluorinated heteroaromatics. Reaction of (1) with pentafluoropyridine gives a mono-substituted product. Mono- and di-substituted products are obtained with tetrafluoro-pyridazine and -pyrimidine, and fluoride ion catalysed isomerisation is observed. The mechanistic consequences of this are discussed. Reaction of (1) with trifluoro-1,3,5- triazine gives a tri-substituted product.