Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
1999-04-09
2002-01-08
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C560S011000, C560S012000, C560S018000
Reexamination Certificate
active
06337418
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates a process for the preparation of substituted aromatic carboxylic acid esters. In particular the invention relates a process for the preparation of nitro-substituted aromatic carboxylic acid esters and thioether-substituted aromatic carboxylic acid esters. Such aryl esters are useful intermediates in the preparation of agrochemicals and agrochemical intermediates.
2. Description of the Related Art
Aryl 1,3-diketones are important synthetic intermediates for a variety of industrially-produced chemicals, such as herbicidal isoxazol derivatives. For example, EP 470856 describes various herbicidal isoxazole derivatives and a process for their preparation from aryl 1,3-diketones. WO 97/28122 describes the preparation of 1-aryl-3-cyclopropyl-1,3-diketones as intermediates used to prepare agrochemicals (e.g. herbicides, pesticides). These 1,3-diketones can be prepared by reacting a substituted acetophenone with a cyclopropanecarboxylic acid ester. However, in addition to the difficulty of preparing the starting substituted acetophenone, the reaction only affords a moderate yield of the desired 1,3-diketone. Aryl 1,3-diketones can also be prepared, as described in WO 95/00476, by hydrolysis of &bgr;-aminovinyl ketones resulting from the reaction between a ketone and a substituted benzonitrile. WO 95/00476 also discloses that reacting a ketone with a substituted benzoic acid ester (prepared from the hydrolysis and subsequent esterification of an aromatic nitrile) also leads to the formation of aryl 1,3-diketones.
Preparation of benzoate esters by the metal-catalyzed carbonylation of an unsubstituted aryl halide substrate, especially an aryl iodide substrate, in alcohol is a well-known process. See, e.g Schoenberg et al,
J. Org. Chem
., 39, 3318 (1974); Stille and Wong,
J. Org. Chem
., 40, 532 (1975); Takeuchi et al,
J. Chem. Soc., Chem. Commun
., 351 (1986); Hicai et al,
Bull. Chem. Soc. Jpn,
48, 2075 (1975); Ito et al,
Bull. Chem. Soc. Jpn
., 48, 2091 (1975); Takahashi et al,
Chem. Lett
., 369 (1980). While aryl bromide substrates are moderately active in such reactions, aryl chlorides are generally inert, although limited success has been achieved with aryl chloride substrates using customized catalysts.
Metal-catalyzed reductive carbonylation of nitroaromatic compounds in alcohol is also a well-known process. Sundermann, R., et al.,
Appl. Homogeneous Catal. Organomet. Compd
., 2, 1072-1080 (1996). Under such reaction conditions reduction of the nitro group results affording aniline derivatives or related compounds. For example, the reaction of nitroarenes with carbon monoxide in alcohols with catalytic rhodium complexes results in the formation of urethanes. Id. Accordingly, since the nitro group is prone to reduction, the metal-catalyzed carbonylation of aromatic substrates substituted with both a halo and a nitro group in alcohols is generally avoided.
Thus there still exists a need in the art for a method of preparing nitro-substituted aromatic carboxylic acid esters from nitro-substituted aryl halide substrates under metal-catalyzed carbonylation reaction conditions without reduction of the nitro group. Such compounds are useful precursors for the preparation of 1,3-diketone agrochemical intermediates.
SUMMARY OF THE INVENTION
The invention answers the need in the art by providing a simple and efficient process to prepare nitro-substituted aromatic carboxylic acid esters from nitro-substituted aryl halides. More particularly, the invention provides a process for the preparation of a nitro-substituted aromatic carboxylic acid ester by reacting a nitro-substituted aryl halide, in the absence of water and oxygen, with carbon monoxide and an alcohol in the presence of a metal catalyst and a proton acceptor.
The invention also provides a simple and efficient process for the preparation of a thioether-substituted aromatic carboxylic acid ester from a nitro-substituted aromatic carboxylic acid ester. Specifically, the process of the invention involves reacting a nitro-substituted aromatic carboxylic acid ester with a thiolate anion.
The invention further provides a one-pot synthesis of a thioether-substituted aromatic carboxylic acid ester from a nitro-substituted aryl halide. According to the invention, a one-pot synthesis reacts a nitro-substituted aryl halide is reacted, in the absence of water and oxygen, with carbon monoxide and an alcohol in the presence of a metal catalyst and a proton acceptor to form the corresponding nitro-substituted aromatic carboxylic acid ester. Without being isolated, the nitro-substituted aromatic carboxylic acid ester is then reacted with a thiolate anion to form the corresponding thioether-substituted aromatic carboxylic acid ester.
DETAILED DESCRIPTION OF THE INVENTION
The invention relates to a process for the preparation of a nitro-substituted aromatic carboxylic acid ester under metal-catalyzed carbonylation reaction conditions. In particular, the invention relates to a process for the preparation of a nitro-substituted aromatic carboxylic acid ester in which a nitro-substituted aryl halide is reacted, in the absence of water and oxygen, with carbon monoxide and an alcohol in the presence of a metal catalyst and a proton acceptor to form the corresponding nitro-substituted aromatic carboxylic acid ester. According to a process of the invention, the halide of the nitro-substituted aryl halide is replaced with or converted to an ester group with little to no, i.e. minimal, reduction of the nitro group. The process is outlined in Scheme A below:
The nitro-substituted aryl halide 1 may be any aryl halide substituted with at least one nitro group known in the art. The halide (X) of the nitro-substituted aryl halide 1 may be a halo group such as, for example, chloro, bromo, or iodo. The aryl group (Ar) may be a monocyclic or polycyclic aryl group or a monocyclic or polycyclic heteroaryl group containing at least one heteroatom of N, O, or S. Examples of suitable aryl groups include, for example, phenyl, benzyl, naphthyl, furyl, benzofuranyl, pyranyl, pyrazinyl, thienyl, pyrrolyl, imidazolyl, pyridyl, pyrimidinyl, pyridazinyl, indolyl, indolizinyl, indazolyl, purinyl, isoquinolyl, quinolyl, isothiazolyl, isoxazolyl, phthalazinyl, quinoxalinyl, quinazolinyl, benzothienyl, isoindolyl, anthryl, phenanthryl, and the like. The aryl group (Ar) of the nitro-substituted aryl halide 1 may also be further substituted with, for example, substituents R′. As discussed here, R′ may be linear or branched, substituted or unsubstituted. Possible R′ substituents include, but are not limited to, C
1
-C
10
alkyl, C
2
-C
10
alkenyl, C
2
-C
10
alkynyl, C
4
-C
10
aryl or heteroaryl, ether, thioether, nitro, trifluoromethyl, fluoro, cyano, and acyl group.
According to the invention, the nitro-substituted aryl halide 1 contains at least one nitro group. Any one nitro group may be adjacent to or at any other position relative to the halo group on the aryl group. For example, if the aryl group is a phenyl group, a nitro group may be substituted at the ortho-, meta- , or para- position. In a preferred embodiment of the invention, the nitro-substituted aryl halide 1 is an ortho-substituted aryl halide, ie. at least one nitro group is ortho to the halo group.
In a preferred embodiment of the invention, the nitro-substituted aryl halide 1 is a nitro-substituted aryl halide of formula (I):
In formula (I), X is a halo group as described above, n is an integer from 1-4, and R′ is, independently, as described above or may together with the phenyl group form a substituted or unsubstituted fused polycyclic ring system. In a more preferred embodiment of the invention, in formula (I), n is 1 and R′ is a trifluoromethyl group. In another more preferred embodiment of the invention, in formula (I), n is 1, R′ is a trifluoromethyl group and is para to halide X, and the nitro group is ortho to halide X.
A process of the invention should be carried out under sufficient carbon
Boaz Neil W.
Coleman M. Todd
Hightower Timothy R.
Blake Esq. Michael J.
Deemie Robert W.
Eastman Chemical Co.
Graves Bernard J.
Killos Paul J.
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