Method for producing o-chloromethyl benzenecarbonyl chlorides

Details Method for producing o-chloromethyl benzenecarbonyl chlorides Method for producing o-chloromethyl benzenecarbonyl chlorides

2002-05-23

2004-05-11

Nazario-Gonzalez, Porfirio (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic halides

C549S307000

Reexamination Certificate

active

06734322

ABSTRACT:

The present invention relates to a process for preparing o-chloromethylbenzoyl chlorides of the formula I,
in which R
1
to R
4
are as defined above, with gaseous or different and are hudrogen, C
1
-C
4
-alkyl, halogen or trifluoromethyl, by reacting benzo-fused lactones of the formula II
in which R
1
to R
4
are as defined above, with gaseous or liquid phosgene,its dimers or trimers. liquid phosgene, its dimers or trimers.
TECHNICAL FIELD
o-chloromethyl-substituted benzoyl chlorides are important intermediates for preparing, for example, pesticidally active compounds as described in the patents EP-A 460 575, EP-A 463 488, WO-A 95/18789, WO-A 95/21154 and WO-A 97/15552.
o-Chloromethyl-substituted benzoyl chlorides can be prepared, for example, by reacting benzo-fused lactones with thionyl chloride or phosgene.
BACKGROUND ART
EP-A 676 389 describes the preparation of o-chloromethylbenzoyl chlorides from benzo-fused lactones using thionyl chloride in the presence of a catalyst. To achieve complete conversion, reaction temperatures of 160-170° C. are required, at which thionyl chloride is already partially decomposed, resulting in the formation of troublesome byproducts.
In WO-A 99/16743, the reaction with thionyl chloride is carried out in the presence of a quaternary ammonium salt and a Lewis acid at 90-100° C. However, quaternary ammonium salts are problematic from an environmental point of view and have the following technical disadvantages: owing to sublimation, parts of the plants may become blocked. Furthermore, the salts are hygroscopic, which may lead to water being introduced and to a higher consumption of chlorinating agent. Finally, the ammonium salts interfere with the distillative purification of the o-chloromethylbenzoyl chlorides.
Carrying out the reaction using thionyl chloride as chlorinating agent is disadvantageous since sulfur dioxide, which has to be worked-up or neutralized, is formed as coproduct in the synthesis. If the chlorinating agent used is phosgene, carbon dioxide, which does not have to be disposed of, is the only byproduct.
EP-A 583 589 describes a process for preparing o-chloromethylbenzoyl chlorides by phosgenation of benzo-fused lactones in the presence of a catalyst at 170-180° C. In contrast to thionyl chloride, phosgene is thermally stable under these conditions; however, the handling of phosgene and its hold up in the condenser at the high temperatures involved is made more difficult by increased safety precautions. Furthermore, under these conditions, the reaction product is under high thermal stress, which may result in its partial decomposition.
In WO 97/12854, triarylphosphine oxides are used as special catalyst type for the reaction, owing to which the use of hydrogen chloride can be dispensed with; however, this does not result in an improvement in the required reaction conditions with respect to the objectionably high reaction temperatures and the resulting safety precautions required.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide an economical process, capable of being carried out on an industrial scale, for preparing o-chloromethylbenzoyl chlorides which does not have the abovementioned disadvantages and still affords high yields.
We have found that this object is achieved by the process mentioned at the outset, which comprises carrying out the reaction with phosgene, its dimers or trimers in the presence of catalytic amounts of a Lewis acid and catalytic amounts of a phosgenation catalyst.
The starting materials used are benzo-fused lactones (phthalides) of the formula II,
in which R
1
to R
4
can be identical or different and are hydrogen (H), C
1
-C
4
-alkyl, halogen (fluorine, chlorine, bromine or iodine) or trifluoromethyl. Preference is given to using unsubstituted phthalide.
The chlorinating agent used is preferably gaseous or liquid phosgene. Furthermore, it is also possible to use dimers (trichloromethyl chloroformate, “diphosgene”) or trimers of phosgene (bistrichloromethyl carbonate, “triphosgene”) or mixtures of these chlorinating agents.
Suitable phosgenation catalysts are, in particular, nitrogen compounds and phosphorus compounds. Examples which can be considered are N,N-disubstituted formamides, hexaalkylguanidinium salts, trialkylphosphines or triarylphosphines which may be substituted or unsubstituted in the aryl moiety, trialkylphosphine oxides or triarylphosphine oxides which may be substituted or unsubstituted in the aryl moiety, N-substituted imidazoles and substituted or unsubstitited pyridines. Particular preference is given to the pyridines of the formula IIIa,
where R is hydrogen or methyl, and to phosphine oxides of the formula IIIb,
in which R
1
to R′″ can be identical or different and are C
1
-C
10
-alkyl or unsubstituted or C
1
-C
4
-alkyl-substituted phenyl and the index n is 0 or 1. Particular preference is given to 3-methylpyridine (&bgr;-picoline) and unsubstituted triphenylphosphine oxide.
The use of liquid trialkylphosphine oxides has, in particular, technical advantages (no need to handle solids, easier discharge of the distillation residue during purification). The tri-C
6
-C
8
-alkylphosphine oxides available under the trade name Cyanex® (for example. Cyanex® 923 from Cyanamide) are, for example, suitable here. Liquid trialkylphosphine oxides combined with Lewis acids, such as tri(C
1
-C
4
-alkyl) borates and boric acid, have been found to be particularly useful.
The phosgenation catalyst is generally added in amounts of from 0.1 to 20 mol %, based on the amount of benzo-fused lactone used, and is preferably added in amounts of from 1 to 10 mol %.
Suitable Lewis acids are, in particular, boron compounds, such as, in particular, BF
3
, BCl
3
or complexes thereof with oxygen compounds, sulfur compounds or nitrogen compounds, tri(C
1
-C
4
-alkyl) borates and boric acid (H
3
BO
3
) itself. Furthermore suitable are AlCl
3
, alkylaluminum dichlorides and dialkylaluminum chlorides, and heterogeneous Lewis-acidic alumosilicates of the zeolite type. Particular preference is given to BF
3
, BCl
3
and complexes thereof with ether (in particular diethyl ether), water (dihydrate), alcohol (in particular methanol), sulfide (in particular dimethyl sulfide) and amine (in particular ethylamine). Particularly suitable are, for example, BF
3
etherate and BF
3
dihydrate.
The Lewis acid used is particularly preferably boric acid or tri(C
1
-C
4
-alkyl) borate. Such processes give excellent yields and have the advantage that the reaction mixtures are free from fluoride ions. Compared to the analogous reaction where the Lewis acid used is BF
3
, the entire apparatus can be simplified.
The Lewis acid is added in amounts of from 0.1 to 20 mol %, based on the amount of benzo-fused lactone used, preferably in amounts of from 0.5 to 5 mol %.
In a further preferred embodiment of the process, the catalyst used is a complex, formed beforehand, of Lewis acid and the phosgenation catalyst. In general, this complex is employed in a concentration of from 0.1 to 20 mol %, based on the amount of benzo-fused lactone used. The catalyst used is preferably a complex of BF
3
and a methyl-substituted pyridine, and particular preference is given to the BF
3
-&bgr;-picoline complex.
If desired, hydrogen chloride can be introduced in parallel to the introduction of phosgene, to accelerate ring-opening. However, the introduction of hydrogen chloride during the synthesis is preferably dispensed with.
Furthermore, it may be advantageous to employ heterogeneous Lewis-acidic catalysts, such as, for example, zeolites of the faujasite type in which some or all of the exchangeable cations have been replaced by protons. A heterogeneously catalyzed reaction has the advantage that it can be carried out in a fixed bed. The heterogeneous catalyst is employed in amounts of from 0.01 to 10% by weight and preferably in amounts of from 0.1 to 1% by weight, based on the amount of benzo-fused lactone used.
The reaction temperature is generally 110-200° C. and preferably 130-160° C.
The process is prefe

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