Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1997-11-13
1999-08-17
Rotman, Alan L.
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
546307, C07D21309, C07D21373
Patent
active
059395532
DESCRIPTION:
BRIEF SUMMARY
The invention pertains to a process for preparing pyridine-2,6-diamines having at least one primary amino (--NH.sub.2) group, i.e., 2,6-diaminopyridine (DAP) and derivative compounds in which one of the amino groups is a substituted amine (secondary or tertiary).
DAP is a suitable starting material for preparing monomers for rigid rod polymers such as described in WO 94/25506, for dyes, metal ligands, medicines, and pesticides. It is well-known to prepare DAP by means of the Chichibabin reaction, in which pyridine is reacted with sodium amide. This is a complicated reaction requiring fairly severe conditions (e.g., 200.degree. C. at increased pressure). Moreover, the reaction is not economical, since the comparatively expensive sodium amide has to be used in excess amount to counteract dimerisation. Furthermore, it is not known to synthesise monosubstituted DAP (having one secondary amino group), which would in any case be a complex process if the Chichibabin reaction were used.
It is known from U.S. Pat. No. 3,225,041 to prepare 2,6-diamino pyridines in which both amino groups are secondary or tertiary amines. This reaction involves contacting 3-hydroxy glutaronitrile with an excess of a primary or secondary amine, in the presence of a halogen acid (hydrogen halide). The disclosure does not pertain to the synthesis of pyridine-2,6-diamines having at least one primary amino group.
The invention has for its object to provide a simple, economically advantageous method of preparing unsubstituted DAP. It is further envisaged to provide a method by means of which derivatives of DAP can be made in which one of the amino groups is a substituted amine.
To this end the invention consists of a process for preparing pyridine-2,6-diamines having at least one primary amino group in which 3-hydroxy pentane 1,5-dinitrile (3-hydroxyglutaronitrile) is reacted with an ammonium donor in the form of ammonia, a primary or a secondary amine, with the proviso that if the ammonium donor is a primary or secondary amine, the use of hydrogen halide as a catalyst is refrained from.
Thus, in one embodiment, the invention is a process for preparing pyridine-2,6-diamine wherein 3-hydroxy pentane 1,5-dinitrile is reacted with ammonia. In another embodiment, the invention is a process for preparing pyridine-2,6-diamines having one primary and one secondary or tertiary amino group, wherein 3-hydroxy pentane 1.5-dinitrile is reacted with a primary or secondary amine in the substantial absence of hydrogen halide.
The starting material, 3-hydroxy pentane 1,5-dinitrile, can be synthesised by reacting epichlorohydrin with sodium cyanide in aqueous solution at pH 8-10. This pH can be set, e.g., by buffering with magnesium sulphate heptahydrate (MgSO.sub.4.7H.sub.2 O) in a known manner. The desired dinitrile is obtained in a yield of about 60% via this process. According to the invention, it was found that a higher yield, 80%, can be obtained if, instead of the magnesium sulphate buffer, a pH electrode coupled to an automatic burette is employed and hydrochloric acid (or, as the case may be, caustic soda) is added during the reaction in this manner, and the reaction temperature is carefully controlled in the range of 20.degree. to 35.degree. C. Instead of hydrochloric acid, sulphuric acid may be used. In a preferred way to carry out this reaction, epichlorohydrin, sodium cyanide solution and sulphuric acid are dropwise added simultaneously. By thus avoiding the presence of all of the sodium cyanide in the reaction vessel, a lower amount of HCN is present during the reaction, which is safer and which leads to avoiding HCN induced by-product formation. Further, the reaction can be controlled better.
The preparation of DAP by the ring closure reaction of 3-hydroxy pentane 1,5-dinitrile and ammonia can be depicted as follows: ##STR1##
The reaction is carried out in a solvent, at room temperature or above, and preferably at elevated temperature (100-200.degree. C., most preferably 140-160.degree. C.). The molar ratio of ammonium donor to 3-hydroxy pen
REFERENCES:
patent: 3225041 (1965-12-01), Johnson
patent: 3247214 (1966-04-01), Johnson
J. Bernstein et al., "II. Derivatives of 2, 6-Diaminopyridine", Journal of the American Chemical Society, vol. 69, May 1947, pp. 1151-1155.
H.J. Den Hertog et al., "On the Reactivity of Bromine Atoms in Brominated pyridines. Preparation of Some 2:6-Disubstituted Products of Pyridine", Recueil des Travaux Chimiques des Pays-Bas, vol. 55, 1936, pp. 122-130.
K. Inuzuka et al., "The Amino-Imino Tautomerization of 2,6-Diaminopyridine by Interaction with Ethanol".
Reichwein Adrianus Maria
Sikkema Doetze Jakob
Akzo Nobel N.V.
Fennelly Richard P.
Rotman Alan L.
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