Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Patent
1997-05-28
1999-01-05
Raymond, Richard L.
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
564417, C07C20936, C07C21152
Patent
active
058565779
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the preparation of fluoroanilines, in particular of difluoroanilines, from optionally substituted fluorinated nitrated benzene compounds.
Fluoroanilines are synthetic precursors which are of very particular interest in the field of medicaments and plant protection.
However, they are not prepared directly but result from multistage synthetic processes, which makes these products very expensive. With the aim of reducing the cost price of these compounds, it is advisable to use stages in which the yields are as high as possible, in particular the final stage.
The various synthetic processes proposed for arriving at fluoroanilines involve fluorinated nitrated compounds which are subsequently reduced to amines. A specific access route comprises the preparation of a fluorinated, and generally chlorinated, nitrobenzene, in order subsequently to subject it to a hydrogenation operation in order to reduce the nitro functional group to an amine functional group, while hydrogenolysing the possible chlorine atoms, which are thus replaced by hydrogen atoms.
Thus, U.S. Pat. No. 4,140,719 describes a synthesis of 2,4-difluoroaniline involving the hydrogenation of 5-chloro-2,4-difluoronitrobenzene, with a yield of 84%.
Likewise, U.S. Pat. No. 5,294,742 describes the hydrogenation of 2,6-dichloro-3,5-difluoronitrobenzene, to give 3,5-difluoroaniline with a yield of 88.9%.
Such yields are acceptable in the laboratory but imply a certain loss of profit, which it would be advisable to avoid in the light of an industrial application.
In addition, it is to be noted that these yields are accompanied by quantitative degrees of conversion, the remainder of the starting material being converted into compounds of azo or azoxy type but also, as has been found by the present Inventors, into polyanilines by polycondensation, these by-products being regarded as highly toxic. Their presence, even as traces after purification, is thus a major disadvantage for the purpose of the use of the fluoroanilines in the synthesis of medicaments or of products which are in contact with the environment (in particular in products for agriculture).
Thus, the aim of the present invention is to provide a process for the preparation of fluoroanilines, in particular of difluoroanilines, from fluorinated nitrated benzene compounds with a virtually quantitative yield, without significant formation of toxic by-products.
The aim of the invention is in particular to provide a process for the hydrogenation of such fluorinated nitrated benzene compounds which makes it possible to carry out the reduction of the said compounds and optionally the hydrogenolysis of halogen substituents, other than fluorine atoms, selectively with respect to hydrodefluorination.
To this effect, one object of the invention is a process for the preparation of a compound of formula (I) ##STR1## wherein n has a value from 1 to 5,
Z is a radical which is stable under catalytic hydrogenation conditions,
p is less than 5-n, according to which a compound of formula (II) ##STR2## where n, Z and p have the above meanings,
X is a hydrogenolysable radical,
q has a value from 0 to 5-(n+p), catalyst, under hydrogen pressure, carrying out a catalytic reduction reaction and, if appropriate, a hydrogenolysis reaction, characterized in that the compound of formula (II) is introduced gradually into the said medium so that the content of compound of formula (II) in the liquid remains less than or equal to 1000 ppm by mass, in order selectively to form the compound of formula (I).
The compounds where X represents a halogen atom, especially a chlorine atom, and especially chlorodifluoronitrobenzenes, are particularly targeted as starting compounds of formula (II).
The Z radical can be any hydrocarbon radical, optionally comprising at least one heteroatom, which is non-hydrogenolysable, that is to say which is not replaced by a hydrogen atom under catalytic hydrogenation conditions. Such a group can be in particular an alkyl group.
According to the invention, in
REFERENCES:
patent: 5294742 (1994-03-01), Schach
patent: 5629449 (1997-05-01), Albright
Database WPI, Week 8231, Derwent Publications Ltd., London, GB; AN 82-63760e & DD-A-154 214 (VEB Leuna-Werk W Ulrich), Mar. 3, 1982 abrege.
Chemical Abstracts, vol. 120, No. 19, May 9, 1994, Columbus, Ohio, US; Abstract No. 244212h, Mason, James et al. `Synthesis of 2,4-difluoroaniline and 1,3-difluorobenzene from 1,2,4-trichlorobenzen` p. 956; col. 2,; "abrege" & Synth. Commun., vol. 24, No. 4, 1994 pp. 529-532.
Copy of Preliminary International Search Report PCT/FR95/01575 (Mar. 1996).
Cordier Georges
Guidot Gilbert
Marion Philippe
Mercier Claude
Carleton Katherine L.
Raymond Richard L.
Rhone-Poulenc Chimie
Seugnet Jean-Louis
LandOfFree
Process for the preparation of fluoroanilines from fluorinated n does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for the preparation of fluoroanilines from fluorinated n, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the preparation of fluoroanilines from fluorinated n will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-864364