Organic compounds -- part of the class 532-570 series – Organic compounds – Nitriles
Patent
1995-08-18
1997-06-10
Richter, Johann
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitriles
558315, C07C25314, C07C25316
Patent
active
056377509
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/GB94/00277 filed Feb. 11, 1994.
This invention relates to a chemical process and more particularly to a method for the preparation of ortho-hydroxy substituted aromatic nitriles.
The preparation of aromatic nitriles by subjecting the corresponding aldoximes to the action of dehydrating agents is a well documented reaction, a number of suitable dehydrating agents having been described in the prior art. The aldoximes themselves may be obtained in conventional manner by reacting the corresponding aromatic aldehydes with hydroxylamine. In practice, the hydroxylamine is usually employed in the form of a salt, for example hydroxylammonium sulphate or chloride, and the reaction is performed in the presence of an acid-binding agent such as sodium carbonate which reacts with the liberated acid forming sodium sulphate or chloride, which has to be disposed of, and carbon dioxide. Since the reaction is commonly carried out in a two-phase aqueous and organic solvent medium, the evolution of carbon dioxide can cause loss of organic solvent with economic and environmental consequences unless appropriate and often expensive precautions are taken.
It is also known to prepare nitriles directly from the corresponding aldehydes. Since hydroxylamine or a material capable of generating hydroxylamine in situ is generally employed as one of the reactants, the reaction is assumed to proceed via the intermediacy of aldoximes but their isolation can be avoided. Thus, Ganboa and Paloma (Synthetic Communications, 13(3), 219-224, 1983) have described the preparation of aromatic nitriles by a one-pot method from aldehydes, hydroxylamine hydrochloride, magnesium sulphate (presumably functioning as dehydrating agent) and p-toluenesulphonic acid as catalyst. The same authors (Synthetic Communications, 13(12), 999-1006, 1983) have also described a one-pot method for preparing aromatic nitriles from aldehydes, hydroxylamine hydrochloride or nitromethane in acetic acid media using polyphosphoric acid as dehydrating agent.
The aromatic nitriles prepared by the dehydration of aldoximes or directly from aldehydes have included 2-hydroxybenzonitrile, a chemical intermediate useful in the production of agricultural chemicals. The preparation of this compound by heating salicylaldoxime in acetic anhydride has been described by Victor Meyer (Chem. Ber., 26, 1254, 1893) and the preparation of the same compound by refluxing a solution of salicylaldehyde in formic acid with hydroxylamine hydrochloride and sodium formate has been reported by van Es (J. Chem. Soc., 1965, 1564).
It has now been found that ortho-hydroxy substituted aromatic nitriles (hereinafter referred to as 2-hydroxybenzonitriles) can be smoothly and economically prepared from 2- hydroxyarylaldehydes if the latter are used, at least partially, in the form of a salt and/or complex of certain metals as hereinafter described. In some cases, a much faster oximation reaction occurs than is the case in the conventional processes and, furthermore, integration of the oximation reaction with a formylation for preparing the aldehyde allows additional operational savings.
Accordingly, the present invention provides a method for the preparation of a 2-hydroxybenzonitrile which comprises reacting hydroxylamine with a 2-hydroxyarylaldehyde which is at least partially in the form of a salt and/or complex of a metal of Group II, Group III, Group IVA or Group VIA of the Periodic Table and dehydrating the 2-hydroxyarylaldoxime so formed.
The Periodic Table referred to herein is the one designated as the "previous IUPAC form" on the front inside cover of the 74th edition of the "Handbook of Chemistry and Physics" published by CRC Press.
As examples of 2-hydroxyarylaldehydes which may be used in the method of the invention, there may be mentioned salicylaldehyde and ring-substituted salicylaldehydes wherein the aromatic ring may carry from one to four substituents in addition to the hydroxy and formyl groups. Examples of suitable substituents include halogen atoms and alkyl
REFERENCES:
patent: 4133834 (1979-01-01), Pickens
Van Es: "A Convenient one-step conversion of aldehydes into nitriles", Journal of the Chemical Society, 1965, p. 1564.
Ganboa, et al: "Reagents and synthetic methods 23. Easily one-flask conversion of aromatic aldehyde to nitriles", Synthetic Communications, vol. 13, No. 3, 1983, pp. 219-224.
Casiraghi, et al: "Selective Reactions using Metal Phenoxides. Part 1. Reactions with Formaldehyde", Journal of the Chemical Society, 1978, pp. 318-321.
Richter Johann
Sackey Ebemezer
Zeneca Limited
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