Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1992-03-24
1994-08-09
Rotman, Alan L.
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
564463, C07D21318, C07D21320, C07C21162
Patent
active
053367758
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of producing tertiary amine-sulphur trioxide complexes of the general formula ring in pyridine to which chlorosulfonic acid is added to dissolve a tertiary amine in a chlorinated organic solvent.
Tertiary amine-sulphur trioxide complexes represent very important reagents which have found multiple uses, for example in the sulfation of dyes, carbohydrates and sterols or also in the sulfonation of polycyclic compounds such as acid-sensitive heterocycles (E. E. Gilbert, Chem. Rev. 549, (1961). In principle, they can be prepared by reacting sulphur trioxide with the corresponding amine in the gaseous phase or in organic solvents (U.S. Pat. No. 2,507,944, Chem. Abstr, 45, 873, 1951). However, the handling of sulphur trioxide presents great difficulties in industrial production. A method suitable for industrial use is the reaction mentioned at the outset of tertiary amine with chlorosulfonic acid in an organic solvent. But with this reaction only small yields are obtained because, of the two mols of amine used, one always combines with hydrogen chloride to form amine hydrochloride (R.sub.3 N.HCl). With the addition of strong alkalis, such as, e.g., sodium hydroxide, there is of course basically the possibility of again recovering the amine from the hydrochloride formed, but this is very costly and hardly economical, for the pertinent reaction is possible only in an aqueous medium. The hydrochloride (R3N.HCl) must first be separated from the amine-sulphur trioxide complex (R.sub.3 N:SO.sub.3) by dissolving it in water and the resulting solution transferred to a separate reactor. Only then can the sodium hydroxide be added (in excess). The tertiary amine again remaining must ultimately also be separated from the water, e.g., by fractional distillation, and dried before it is again available as the starting product.
It is the object of the present invention to provide a method that is easy to handle on a commercial scale for the preparation of amine-sulphur trioxide complexes with which a considerably better yield can be achieved, in an economical manner.
According to the invention this as well as other objects are solved by a method characterized in what is stated in the characterizing portion of claim 1. Preferred embodiments of the invention are characterized in the dependent claims.
In the method pursuant to the invention, gaseous ammonia is passed into the reaction mixture in order to recover amine from amine hydrochloride previously formed as by-product. It is possible to recover the amine by means of ammonia because amine hydrochloride is more soluble than ammonium chloride. The recovered amine reacts with the chlorosulfonic acid still present to form the desired R.sub.3 N:SO.sub.3 complex. In this way the amine is recovered especially advantageously in the same reaction vessel as well as in the same organic solvent.
If a tertiary amine is used which is a stronger base than ammonia, the end of the reaction is reached when the suspension is alkaline. If a tertiary amine is used which is e weaker base than ammonia, such as e.g. pyridine, ammonia is preferably passed into the reaction mixture only until the latter shows a pH of 4. With a pH above 4 the tertiary amine would be expelled by the ammonia in the desired complex, i.e., the yield would decrease.
The ammonium chloride formed can be dissolved by the addition of water and agitation. Finally, the desired tertiary amine-sulphur trioxide complex can be separated by filtration, washed and, after drying, obtained as dry final product.
As solvent, 1,2-dichloroethane, chloroform, carbon tetrachloride or methylene chloride is preferably used.
During the reaction the temperature is preferably set at a value between 0.degree. and 30.degree. C.
The method according to the invention exhibits the following advantages: and readily carried out economically on a commercial scale. Yields of 80-94% can be achieved. vessel used for the desired reaction itself. means of sodium hydroxide as reagent and its subsequent separation from th
REFERENCES:
patent: 5329087 (1993-08-01), Zeljko et al.
Guberovic Zeljko
Hohnjec Marijan
Kuftinec Josip
Oklobzija Milan
Pfizer Inc.
Rotman Alan L.
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