Organic compounds -- part of the class 532-570 series – Organic compounds – Nitriles
Patent
1999-08-17
2000-12-19
Tsang, Cecilia
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitriles
558338, 558343, C07C25300
Patent
active
061629421
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a process for preparing aromatic nitriles from corresponding chloroaromatics by reaction with cyanides. Substituted benzonitriles and other aromatic nitriles are intermediates which are frequently employed in the preparation of pharmaceutical and agricultural active compounds.
BACKGROUND OF THE INVENTION
It is known that aryl halides can be converted into aromatic nitrites using alkali metal cyanides in the presence of catalysts, for example nickel complexes. Adv. in Chem. Series 132: Homogeneous Catalysis II, 252-273 (1974) describes the nickel-catalysed cyanation of aryl halides with alkali metal cyanides in detail. The catalysts used were Ni(0) or Ni(II) complexes having generally mono- or bidentate arylphosphine ligands. The solvents used were alcohols, such as methanol and ethanol, and dipolar-aprotic solvents, such as dimethylformamide. It is only possible to carry out the reaction with good yields if the concentration of the cyanide ions is controlled exactly. Acetone has been employed as solvent only for the cyanation of unsubstituted chlorobenzene. Here, a selectivity of 82% was achieved, at a conversion of 58%, and 10% of an undesired coupling product (biphenyl) were obtained. For a process that is to be carried out on an industrial scale, these are very unfavourable values. Later, it was found that the catalyst is cyanated irreversibly at higher cyanide concentrations see Bull. Chem. Soc. Jpn. 61, 1985 (1988) and J. Organomet. Chem. 173, 335 (1979)).
EP-A 384 392 describes the cyanation of optionally halogen-, formyl- or trifluoro-methyl-substituted chloro- or bromobenzene in the presence of catalysts prepared in situ from nickel chloride. The reaction is carried out in anhydrous lower alcohols or dipolar aprotic solvents. Here, the yields are frequently unsatisfactory. In many cases, a further disadvantage is dehalogenation, which proceeds as a side reaction. The preferred solvent--acetonitrile owing to its toxicity and tetrahydrofuran owing to its tendency to form peroxides--can be handled on an industrial scale only with great expense.
For 2-thio-3-amino-chlorobenzene, WO 96/11906 describes the cyanation in the presence of phosphine nickel catalysts in aprotic polar solvents. Not to mention the specific substitution pattern of the substrate, the 11-22 mol % of tetrakis-triphenylphosphine-nickel constitute uneconomically high amounts of catalyst. EP-A 613 720 likewise describes a process for preparing aromatic nitriles in which the preferred solvent employed is tetrahydrofuran, which has the above-mentioned disadvantages.
SUMMARY OF THE INVENTION
This invention, accordingly, provides a process for preparing aromatic nitriles of the formula substituted biphenyl, optionally substituted phenyl which contains a fused-on 3- to 5-membered heterocycle, or represents hetaryl which contains 5 to 10 ring members and is optionally substituted, possible substituents being up to five identical or different substituents selected from the group consisting of C.sub.1 -C.sub.12 -alkyl, C.sub.1 -C.sub.12 -halogenoalkyl, C.sub.1 -C.sub.12 -alkoxy, C.sub.1 -C.sub.12 halogenoalkoxy, C.sub.1 -C.sub.6 -alkylsulphonyl, C.sub.1 -C.sub.6 -halogenoalkylsulphonyl, C.sub.1 -C.sub.12 -alkylcarbonyl, C.sub.1 -C.sub.12 -alkoxycarbonyl, fluorine, formyl, nitro and cyano, where the C.sub.1 -C.sub.12 -alkyl for its part may be substituted by 1 to 4 C.sub.1 -C.sub.6 -alkoxy groups, nickel (II) complexes with potassium cyanide and/or sodium cyanide, characterized in that the process is carried out in the presence of an optionally cyclic ketone having at least four carbon atoms.
DESCRIPTION OF THE INVENTION
Ketones to be employed according to the invention have, compared with the dipolar aprotic solvents which have hitherto been used, the advantage of lower toxicity and higher stability towards atmospheric oxygen. Compared with acetone, when using the process according to the invention for the cyanation of unsubstituted chlorobenzene, better selectivities are achiev
REFERENCES:
Adv. in Chem. Series 132: Homogeneous Catalysis II, pp. 252-273 (month unavailable) 1974.
Bull. Chem. Soc. of Japan, 61, pp. 9185-1990, Jun. 1988.
Journal of Organometallic Chemistry, pp. 335-339 (month unavailable) 1979.
Chem. Abstracts, vol. 82, No. 13, Mar. 31, 1975, Abstract No. 85632.
Chem. Abstracts, vol. 125, No. 5, Jul. 29, 1996, Abstract No. 58095.
Marhold Albrecht
Rock Michael-Harold
Bayer Aktiengesellschaft
Gil Joseph C.
Murray Joseph
Tsang Cecilia
Van Eyl Diderico
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