Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Patent
1998-12-14
2000-04-11
Kunz, Gary L.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
560 1, C07C 6976
Patent
active
060489987
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a chemical process and more particularly to a process for preparing methyl 2-(chloro- or bromomethyl)phenylacetate which is useful as an intermediate in the manufacture of agricultural compounds.
The compound methyl 2-(chloromethyl)phenylacetate and its method of preparation from o-xylene, via 2-methylphenyl acetonitrile and 2-methylphenyl acetic acid, is disclosed in JP 59-163370 A.
A method of preparing methyl 2-(haloalkyl)phenylacetates, such as the 2-bromoalkyl compounds, by ring opening isochromanones using a hydrogen halide in methanol is mentioned in EP-A-278595. The ring opening of 3-isochromanone using hydrogen bromide is also mentioned in CA 92: 128526t and CA 92: 180829h. However, in both these references the free 2-(bromomethyl)phenylacetic acid is said to be formed, the isochromanone ring being cleaved with either HBr-H.sub.2 SO.sub.4 or HBr in acetic acid.
The preparation of methyl 2-[2-(halomethyl)phenyl]-3-methoxypropenoates by reacting 4-(.alpha.-methoxy)methylene-2H-chromen-3(4H)-one with a thionyl halide optionally in the presence of a solvent and reacting the product so formed with methanol, is described in WO 95/25729. In specific examples, 4-(.alpha.-methoxy)-methylene-2H-chromen-3(4H)-one is reacted with refluxing thionyl chloride. At the end of reaction, excess thionyl chloride is removed and the product so formed then reacted with methanol.
The present invention provides an industrially suitable, one-stage process for the preparation of methyl 2-(chloro- or bromomethyl)phenylacetate from 3-isochromanone which can be carried out at moderate temperatures and which offers environmental advantages in terms of the lower generation of unwanted methyl chloride or methyl bromide by-product.
Thus, according to the present invention, there is provided a process for preparing a methyl 2-(halomethyl)phenylacetate which comprises treating 3-isochromanone with a thionyl halide of formula SOX.sub.2 wherein X is chlorine or bromine, in the presence of methanol.
The process, which is represented by the reaction scheme: ##STR1## may be carried out at a temperature of from -80.degree. C. to 130.degree. C. (under pressure), for example, from -40.degree. C. to 40.degree. C., and typically from 0.degree. C to 30.degree. C. Normally it is carried out keeping the temperature just below 25.degree. C. It is an advantage of the invention process that it can be operated at ambient temperatures.
The amount of thionyl halide used may range from 0.5 moles per mole of isochromanone to any sensible upper limit consistent with practicality. Normally it is in the range of from 1.0 to 2.1 moles per mole of isochromanone and preferably from 1.15 to 1.65. Typically it is about 1.25 moles per mole of isochromanone.
The amount of methanol used may range from 1 mole per mole of isochromanone to any upper limit consistent with practicality. Preferably it is in the range of from 3 to 3.5, typically 3.05 to 3.1 moles per mole of isochromanone.
Normally the invention process is carried out with a suitable diluent. Suitable diluents include methanol and other solvents, such as saturated or aromatic hydrocarbons or their fluorinated or chlorinated derivatives, which are inert to the reactants. When methanol is used as diluent, the total amount of methanol present (diluent and reactant) is, for example, from 9 to 10 moles per mole of isochromanone, typically from 9 to 9.1. For industrial purposes, toluene is a very convenient diluent.
Thus, in one aspect, the invention provides a process for preparing a methyl 2-(halomethyl)phenylacetate which comprises treating 3-isochromanone with 1.0 to 2.1 moles of a thionyl halide of formula SOX.sub.2 (wherein X is chlorine or bromine) per mole of 3-isochromanone in the presence of from 3 to 3.5 moles of methanol per mole of 3-isochromanone in a suitable diluent and at a temperature of from 800.degree. C. to 130.degree. C.
Suitably from 1.15 to 1.65, and more suitably about 1.25, moles of thionyl halide per mole of 3-isochromanone are used.
Suitably from 3.05 to 3.
REFERENCES:
Chemical Abstracts, Rn 13737-37-6, 1997.
Chemical Abstracts, vol. 92, 180829h 1980.
Chemical Abstracts, vol. 92, 128526t 1980.
Jones Raymond Vincent Heavon
McCann Hannah Sallie Robertson
Ritchie David John
Standen Michael Charles Henry
Kunz Gary L.
LeCroy David P.
Zeneca Limited
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