CA1106392A - Recovery of herbicidal esters - Google Patents
Recovery of herbicidal estersInfo
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- CA1106392A CA1106392A CA270,792A CA270792A CA1106392A CA 1106392 A CA1106392 A CA 1106392A CA 270792 A CA270792 A CA 270792A CA 1106392 A CA1106392 A CA 1106392A
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C233/00—Carboxylic acid amides
- C07C233/01—Carboxylic acid amides having carbon atoms of carboxamide groups bound to hydrogen atoms or to acyclic carbon atoms
- C07C233/12—Carboxylic acid amides having carbon atoms of carboxamide groups bound to hydrogen atoms or to acyclic carbon atoms having the nitrogen atom of at least one of the carboxamide groups bound to a carbon atom of a hydrocarbon radical substituted by halogen atoms or by nitro or nitroso groups
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Abstract
A B S T R A C T
Process for the recovery of N-benzoyl-N-(3,4-dihalophenyl)-2-aminopropionic acid esters from mixtures by treatment with an aqueous base, followed by treatment with a water-immiscible organic solvent; acidifying the aqueous phase with a mineral acid;
esterifying the liberated carboxylic acid(s) with a lower alkanol and optionally benzoylating the esterified product.
Process for the recovery of N-benzoyl-N-(3,4-dihalophenyl)-2-aminopropionic acid esters from mixtures by treatment with an aqueous base, followed by treatment with a water-immiscible organic solvent; acidifying the aqueous phase with a mineral acid;
esterifying the liberated carboxylic acid(s) with a lower alkanol and optionally benzoylating the esterified product.
Description
; This invention relates to a process for the recovery of' certain herbicidal esters from mix-tures containing them.
The esters are derived from N~benzoyl-N-(3,l1-dihalophenyl)-2-aminopropionic acids and are of the general formula:
. X
~ COC6H5 Y ~ N - CHCOOR (I) wherein X and Y each represents a fluorine or chlorine atom and ~
represents an alkyl group of 1 to 3 carbon atoms. These compounds and their selectively herbicidal activity against wi]d oa-ts have been described in U.K. patent specif'ications Nos 1,16ll,160 and ~ 1,289,283.
,~ 10 The synthesis of -these esters involves essentially the f'ollowing steps:
~ (a) reac-tion of the appropriate 3~l1-dihaloaniline with a chloro-,~ propionic acid ester; followed by (b) benzoylation of the product with benzoyl chloride.
The crude ester produced in this way contains a considerable amount of impurities in the form of by-products as well as starting and/or intermediate compounds. The crude ester is -therefore purified by crystallization from an organic solvent medium. Unfortunately, a substantial amount of ester, usually about 20% of the total yield of ester, remains in the mother liquor after the crystallization.
Up to now it has not proved possible on the commercial scale to recover further amounts of ester economically ~rom the mother liquors which have consequently been re~arded as waste. A process ~639~
has now been ~ound whereby significarlt amoun-t;s o~ ester may be recovered rrom the mother liquors.
`; Accordingly, the present invention provides a process for -the recovery o~ an ester of' general f'ormula I above from a mother liquor ob-tained af'ter crystallization of -the crude ester ~rom an organic solvent medium~ which comprises:
~ (a) -treating the mother liquor or the resi*ue therefrom with an ;; aqueous alkali metal base to give an aqueous phase containing an alkali metal salt of the carboxylic acid derived rrom the saponiried ester;
(b) contacting the aqueous phase wi-th a substan-tially water-immiscible organic solvent, (c) acidirying -the aqueous phase with a mineral acid;
(d) esterifying the liberated carboxylic acid(s) with an alkanol of 1 to 3 carbon a-toms in the presence of' an acid catalyst, and, optionully, .~
(e) benzoylating the esterif'ied product with a benzoyl halide under substantially anhydrous conditions.
The process o~ the invention will now be described in more detail by ref'erence to the purif'ication of` mother liquors containing ethyl N-benzoyl-N-(3,4-dichlorophenyl)-2-aminopropiorlate. It shou]d be understood, however, that the process details are equally applicable to -the recovery o~ other ester.
The ester is usually crystallized f'rom a mixture of' me-thyl isobutyl ketone and hexane. A typical residue obtained by removing the solvent f'rom the mo-ther liquor contains about 30%w o~ -the ester, the remaining 70% being impurities. Examples o~ -these impurities are 3~3Z
(i) o-ther esters such as 0-(N-benzoyl-N-3,l~-dichlorophenyl-2-aminopropionyl)-ethyl lactate, ethyl N-benzoyl-N-(3,4-dichlorophenyl)-3-aminopropionate, ethyl N-(3,4-dichlorophenyl)-'-aminopropionate, ethyl benzoate, (ii) acids such as N-benzoyl-N-(3,1~-dichlorophenyl)-2-aminopropionic ac;d, N-(3,4-dichlorophenyl)-2-aminopropionic acid, - 10 benzoic acid, ~-~ and (iii) amides such as N-benzoyl-3,4-dichloroaniline, N-ethyl-N-benzoyl-3,4-dichloroaniline, N-butyl-N-benzoyl-3,4-dichloroaniline.
The treatment of the mother liquor or the residue therefrom with :
the aqueous alkali metal base (step (a~) converts the esters and acids present into water soluble alkali metal salts which are taken up in the aqueous phase. The treatmen-t is preferably carried ou-t using an aqueous solution containing 5 to 20/w sodium hydroxide.
The temperature is preferably from 50 to 100C.
In step (b~ the aqueous phase is contacted wi-th a sub-s-tantially water-immiscible solvent in order to remove any organic ; compounds which are not in the rorm of alkali metal salts. The solvent may be a halogenated (chlorinated) hydrocarbon such as tetrachloroethylene or dichloroethane3 an ether such as diethyl ether, a ketone such as methyl isobutyl ketone, or mixtures thereof with, for example, an aliphatic hydrocarbon such as hexane.
_ 1~ _ 63~3;2 The aqueous phase is treated in step (c) with mineral acid, preferably sulphuric acid in order to convert the salts to the corresponding carboxylic acids. This treatment is preferably carried out at 30-50C. The liberated acids are preferably extrac-ted from the aqueous phase with a substantially wa-ter-immiscible organic solvent, for example a solvent as described above under step (b).
The acids are then esterif;ed suitably under conventional esterification conditions with an alkanol of 1 to 3 carbon atoms ,~ (step (d)). If the alcohol used is e-thanol the product of this s-tage consists mainly of the required ester:
ethyl N-benzoyl-N-(3,4-dichlorophenyl)-2-aminopropionate, ethyl N-(3,4-dichlorophenyl-2-aminopropionate ("desberlzoyl es-ter"), and e-thyl benzoate.
It will be appreciated that it i5 possible to use at this stage a different alkanol from the one corresponding to the es-ter originally present in the mother liquor. It is thus possible by using the process of the invention -to obtain amounts of different esters (see Example III below). ~fter the esterification the product is preferably washed with water and then dried.
The esterified mixture may op-tionally be benzoylated (step (e)) with a benzoyl halide, preferably the chloride, under substantially anhydrous conditions. Preferably the amount o~ benzoyl halide is an ~0-100% molar excess over that theoretically required ~or re-action with the "desbenzoyl ester" present. In this way "desbenzoyl ester" is converted to more of the required es-ter and so the process can give an overall increase in the amolmt of the required ester :
~ which c~n be rocovered.
.~
.
t;3~312 :.
,, The various s-tages o~ -the process are illustrated further in the f~llowing Examples.
~XAMPL~ I
:"' ~- The starting material was a mother liquor derived from the crystallization of crude ethyl N-benzoyl-N-(3,4-dichlorophenyl)-2-aminopropionate ~rom a mix-ture of methyl isobu-tyl ketone and hexane, and containing 19.6 %w of the ester. The solven-t mixture was distilled off to give a residue having the following composition:
ethyl N-benzoyl-N-(3~ dichlorophenyl)-2-amino-propionate ("es-ter") 30 o%w - 0- ~N-benzoyl-N-(3,ll-dichlorophenyl)-2-amino-propiony~ ethyl lactate 9.3%w ethyl N-(3,4-dichlorophenyl)-2-aminopropionate ("desbenzoyl ester") 3.0%w ethyl benzoate 1.8%w remainder 55.1%w The remainder contained unspecified amoun-tsof ~ N-benzoyl-N-(3,4-dichlorophenyl)-2-a~inopropionic acid ("acid") -~ and N-(3,4-dichlorophenyl)-2-aminopropionic acid ("desbenzoyl acid").
(a) ~eaction with aqueous sodium hydroxide A 10~w aqueous solution of sodium hydroxide (2301 kg) was added to the residue (1725 kg) over a period of 0.5 hour at 60-65~ with vigorous stirring. The mixture was then hea-ted at 65C for a ~urther one hour. ~lternatively the mo-ther liquor i-tself could be treated directly with -the base; in this case the organic layer was r~moved before the next step.
(b) F traction The aqueous mixture from (a) was then extracted three t;mes each with 1620 kg tetrachloroethylene at 60C. Alterna-tively the aqueous 63~
; mixture could also be extracted twice with 370 kg Or a 25%w mixture of methyl iso'butyl ketone in hexane.
,- (c) Acidification Concentrated sulphuric acid (95%w, 378 kg) was added -~o the aqueous mixture which was then extracted once with tetrachloroethylene : (486 kg) or methyl isobutyl ketone (370 kg). The extract was separated and the tetrachloroethylene was distilled off at il10C under reduced pressure. The residue thus obtained had the following compositiorl:
. "acid" 64.3%w "desbenzoyl acid" 8.3%w benzoic acid 4.11%w remainder 22.9%w (d ? Es terirication ....
The residue (1054 kg) was mixed with 99%w e-thanol (360 kg) and 95%w sulphuric acid ( 113 kg~ and the mixture was heated under reflu~
for 0. 5 hour. After this aqueous ethanol was distilled off and ,~ simultaneously fresh 99~w ethanol was added to the mixture at a ra-te'~ e~ual to the distillation rate. The total reaction time was 4-6 hours, ' after which ethanol was removed under reduced pressure. The residue : 20 obtained was diluted with toluene (2280 kg) and the organic phase was washed first with water ( 800 kg) and then with 5%w aqueous sodium bicarbonate solution (824 kg). The -toluene solution was dried by , dis-tillation of -the -toluene/water azeotrope un-til the temperature of the solution reached 125 C. In an alternative procedure the ; 25 toluene was replaced by methyl isobutyl ketone ( 1850 kg).
(e) Benzoylation Benzoyl chloride ( 82 kg~ was added to the toluene solution over a period of 0. 25 hour and the mixture was heated under reflux for a further one hour. The mixture was diluted with toluene (1000 kg) and 3~3;~
:'' then s-tirred first with wa-ter (300 kg) at 60 C followed by 5%w aqueous sodium bicalibonate solution (915 kg) again a-t 60C. The toluene was then removed Erom -the solution under reduced pressure : ,.
i~ (40 mm Hg) and the residue was then stripped wi-th nitrogen at 140 C
:
and a pressure of 25 mm ~Ig. The analysis of the product (111ll kg) ~- obtained was:
"ester" 73.6%w "desbenzoyl ester" o.6%w ethyl benzoate 2.7%w remainder 23.1%w It will be seen tha-t the concentration of "ester" in -the product is more than double that in -the original star-tirlg material, and, moreover, the actual weight of "ester" present has been raised from 531 kg to 820 kg.
This product, optionally combined with crude product from the ~ es-ter synthesis, may be crystallized from 20-25%w me-thyl isobu-tyl ke-tone -~ in hexane (weight ratio solid: solvent = 1.5:1) -to give pure es-ter.
-E~A~LE II
The starting material was a mother liquor from -the crystalliza-tion of crude isopropyl ~-benzoyl-1'~-(3-chloro-~-fluorophenyl)-2-amino-.:
propionate irom me-thyl isobu-tyl ketone/hexane. This mo-ther liquor was concentrated -to give a residue containing 60%w of the ester and 2%w of the corresponding "desbenzoyl ester".
(a) Reaction with aq~ueous sodium hydroxide The residue (327 g) was s-tirred vigorously with a 10% aqueous solution of sodium bydroxide (437 g) for three hours at 90-95 C.
(b) Extrac-tion c The agueous mixture was then ex-tracted three times each with 300 g o~ -tetractlloroe-thylene at 60-70C.
'--1~63'~1;3Z
~' (c) Acidi~ication ____ The aqueous mixture was therl acidified with 95%w suLphuric acid (65 g) and extracted with tetrachloroethylene (2000 g). The tetrachloroethylene was removed ~rom the extract under reduced pressure (ll~0 C/100 mg llg). At this stage the residue contained ` 69.5%w "acid" and 7.2%w "desbenzoyl acid".
(d) Esteri~ication The residue (270 g) was mixed with isopropanol (95 g) and 95%w sulphuric acid (27 g~ and the mixture was heated under re~lux for o.5 hour. ~-ter this aqueous isopropanol was distilled of~` and simultaneously ~resh isopropanol was added at a rate equal to the distilla-tion rate. The to-tal reaction time was 5 to 6 hollrs a~ter which the excess isopropanol was removed under reduced pressure.
The residue was taken up in toluene and the organic phase was washed first with water (210 g~ and then 5%w sodium bicarbonate solution (210 g) at 50 C. The toluene solution was then dried by distillation o~ the toluene/water azeotrope.
(e) Benioylation Benzoyl chloride (25 g) was added to the toluene solution over a period o~ 0. 25 hour at 125 c, and the mixture was then stirred under re~l-ux ~or a further one hour. rrhe mix-ture was dilu-ted with toluene (250 ~ and then stirred with water (65 g) at 70C. The organic phase was then washed wi-th 5%w sodiuml bicarbona-te solution and the toluene was removed under reduced pressure. The residue was then stripped at 11~0 C with nitrogen under reduced pressure ( 25 mm Hg).
The residue (24O g) had -the ~ollowing composition:
, , _ 9 _ ' - - - .- ...... .
36~Z
:.' '"`
Isopropyl N-benzoyl-N-(3-chloro-4-fluorophenyl)-2-.. ~ aminopropionate 87.6%w "desbenzoyl ester" ~ 0.1%wisopropyl benzoate 2. 4~oWremainder 10%wThis crude "ester" could be readily recrystallized from a methyl isobutyl ketone/hexane mixture.
EXAMPLE III
The starting material was the same as that used i.n Example II
and steps (a), (b) and (c~ of the process were identical to those . of ExQ~ple II.
(d) Esteri~ication This step was carried out using 245 g of the residue ~rom step (c~, methanol (45 g) and 95%w sulphuric acid (25 g). The esterification conditions and work-up procedure were as described in Example II (d).
(e~ Benzoylation This step was carried out using -the procedure o:~ Example II(e).
The residue ob-tained (230 g) had the ~ollowing composition:
methyl N-benzoyl-N-(3-chloro-4-~luorophenyl)-2-aminopropionate 88.5%w methyl N-(3-chloro-4-~luorophenyl~-2-amino-propionate 0.2%w isopropyl N-benzoyl-N-(3-chloro-4-.~luorophenyl)-
The esters are derived from N~benzoyl-N-(3,l1-dihalophenyl)-2-aminopropionic acids and are of the general formula:
. X
~ COC6H5 Y ~ N - CHCOOR (I) wherein X and Y each represents a fluorine or chlorine atom and ~
represents an alkyl group of 1 to 3 carbon atoms. These compounds and their selectively herbicidal activity against wi]d oa-ts have been described in U.K. patent specif'ications Nos 1,16ll,160 and ~ 1,289,283.
,~ 10 The synthesis of -these esters involves essentially the f'ollowing steps:
~ (a) reac-tion of the appropriate 3~l1-dihaloaniline with a chloro-,~ propionic acid ester; followed by (b) benzoylation of the product with benzoyl chloride.
The crude ester produced in this way contains a considerable amount of impurities in the form of by-products as well as starting and/or intermediate compounds. The crude ester is -therefore purified by crystallization from an organic solvent medium. Unfortunately, a substantial amount of ester, usually about 20% of the total yield of ester, remains in the mother liquor after the crystallization.
Up to now it has not proved possible on the commercial scale to recover further amounts of ester economically ~rom the mother liquors which have consequently been re~arded as waste. A process ~639~
has now been ~ound whereby significarlt amoun-t;s o~ ester may be recovered rrom the mother liquors.
`; Accordingly, the present invention provides a process for -the recovery o~ an ester of' general f'ormula I above from a mother liquor ob-tained af'ter crystallization of -the crude ester ~rom an organic solvent medium~ which comprises:
~ (a) -treating the mother liquor or the resi*ue therefrom with an ;; aqueous alkali metal base to give an aqueous phase containing an alkali metal salt of the carboxylic acid derived rrom the saponiried ester;
(b) contacting the aqueous phase wi-th a substan-tially water-immiscible organic solvent, (c) acidirying -the aqueous phase with a mineral acid;
(d) esterifying the liberated carboxylic acid(s) with an alkanol of 1 to 3 carbon a-toms in the presence of' an acid catalyst, and, optionully, .~
(e) benzoylating the esterif'ied product with a benzoyl halide under substantially anhydrous conditions.
The process o~ the invention will now be described in more detail by ref'erence to the purif'ication of` mother liquors containing ethyl N-benzoyl-N-(3,4-dichlorophenyl)-2-aminopropiorlate. It shou]d be understood, however, that the process details are equally applicable to -the recovery o~ other ester.
The ester is usually crystallized f'rom a mixture of' me-thyl isobutyl ketone and hexane. A typical residue obtained by removing the solvent f'rom the mo-ther liquor contains about 30%w o~ -the ester, the remaining 70% being impurities. Examples o~ -these impurities are 3~3Z
(i) o-ther esters such as 0-(N-benzoyl-N-3,l~-dichlorophenyl-2-aminopropionyl)-ethyl lactate, ethyl N-benzoyl-N-(3,4-dichlorophenyl)-3-aminopropionate, ethyl N-(3,4-dichlorophenyl)-'-aminopropionate, ethyl benzoate, (ii) acids such as N-benzoyl-N-(3,1~-dichlorophenyl)-2-aminopropionic ac;d, N-(3,4-dichlorophenyl)-2-aminopropionic acid, - 10 benzoic acid, ~-~ and (iii) amides such as N-benzoyl-3,4-dichloroaniline, N-ethyl-N-benzoyl-3,4-dichloroaniline, N-butyl-N-benzoyl-3,4-dichloroaniline.
The treatment of the mother liquor or the residue therefrom with :
the aqueous alkali metal base (step (a~) converts the esters and acids present into water soluble alkali metal salts which are taken up in the aqueous phase. The treatmen-t is preferably carried ou-t using an aqueous solution containing 5 to 20/w sodium hydroxide.
The temperature is preferably from 50 to 100C.
In step (b~ the aqueous phase is contacted wi-th a sub-s-tantially water-immiscible solvent in order to remove any organic ; compounds which are not in the rorm of alkali metal salts. The solvent may be a halogenated (chlorinated) hydrocarbon such as tetrachloroethylene or dichloroethane3 an ether such as diethyl ether, a ketone such as methyl isobutyl ketone, or mixtures thereof with, for example, an aliphatic hydrocarbon such as hexane.
_ 1~ _ 63~3;2 The aqueous phase is treated in step (c) with mineral acid, preferably sulphuric acid in order to convert the salts to the corresponding carboxylic acids. This treatment is preferably carried out at 30-50C. The liberated acids are preferably extrac-ted from the aqueous phase with a substantially wa-ter-immiscible organic solvent, for example a solvent as described above under step (b).
The acids are then esterif;ed suitably under conventional esterification conditions with an alkanol of 1 to 3 carbon atoms ,~ (step (d)). If the alcohol used is e-thanol the product of this s-tage consists mainly of the required ester:
ethyl N-benzoyl-N-(3,4-dichlorophenyl)-2-aminopropionate, ethyl N-(3,4-dichlorophenyl-2-aminopropionate ("desberlzoyl es-ter"), and e-thyl benzoate.
It will be appreciated that it i5 possible to use at this stage a different alkanol from the one corresponding to the es-ter originally present in the mother liquor. It is thus possible by using the process of the invention -to obtain amounts of different esters (see Example III below). ~fter the esterification the product is preferably washed with water and then dried.
The esterified mixture may op-tionally be benzoylated (step (e)) with a benzoyl halide, preferably the chloride, under substantially anhydrous conditions. Preferably the amount o~ benzoyl halide is an ~0-100% molar excess over that theoretically required ~or re-action with the "desbenzoyl ester" present. In this way "desbenzoyl ester" is converted to more of the required es-ter and so the process can give an overall increase in the amolmt of the required ester :
~ which c~n be rocovered.
.~
.
t;3~312 :.
,, The various s-tages o~ -the process are illustrated further in the f~llowing Examples.
~XAMPL~ I
:"' ~- The starting material was a mother liquor derived from the crystallization of crude ethyl N-benzoyl-N-(3,4-dichlorophenyl)-2-aminopropionate ~rom a mix-ture of methyl isobu-tyl ketone and hexane, and containing 19.6 %w of the ester. The solven-t mixture was distilled off to give a residue having the following composition:
ethyl N-benzoyl-N-(3~ dichlorophenyl)-2-amino-propionate ("es-ter") 30 o%w - 0- ~N-benzoyl-N-(3,ll-dichlorophenyl)-2-amino-propiony~ ethyl lactate 9.3%w ethyl N-(3,4-dichlorophenyl)-2-aminopropionate ("desbenzoyl ester") 3.0%w ethyl benzoate 1.8%w remainder 55.1%w The remainder contained unspecified amoun-tsof ~ N-benzoyl-N-(3,4-dichlorophenyl)-2-a~inopropionic acid ("acid") -~ and N-(3,4-dichlorophenyl)-2-aminopropionic acid ("desbenzoyl acid").
(a) ~eaction with aqueous sodium hydroxide A 10~w aqueous solution of sodium hydroxide (2301 kg) was added to the residue (1725 kg) over a period of 0.5 hour at 60-65~ with vigorous stirring. The mixture was then hea-ted at 65C for a ~urther one hour. ~lternatively the mo-ther liquor i-tself could be treated directly with -the base; in this case the organic layer was r~moved before the next step.
(b) F traction The aqueous mixture from (a) was then extracted three t;mes each with 1620 kg tetrachloroethylene at 60C. Alterna-tively the aqueous 63~
; mixture could also be extracted twice with 370 kg Or a 25%w mixture of methyl iso'butyl ketone in hexane.
,- (c) Acidification Concentrated sulphuric acid (95%w, 378 kg) was added -~o the aqueous mixture which was then extracted once with tetrachloroethylene : (486 kg) or methyl isobutyl ketone (370 kg). The extract was separated and the tetrachloroethylene was distilled off at il10C under reduced pressure. The residue thus obtained had the following compositiorl:
. "acid" 64.3%w "desbenzoyl acid" 8.3%w benzoic acid 4.11%w remainder 22.9%w (d ? Es terirication ....
The residue (1054 kg) was mixed with 99%w e-thanol (360 kg) and 95%w sulphuric acid ( 113 kg~ and the mixture was heated under reflu~
for 0. 5 hour. After this aqueous ethanol was distilled off and ,~ simultaneously fresh 99~w ethanol was added to the mixture at a ra-te'~ e~ual to the distillation rate. The total reaction time was 4-6 hours, ' after which ethanol was removed under reduced pressure. The residue : 20 obtained was diluted with toluene (2280 kg) and the organic phase was washed first with water ( 800 kg) and then with 5%w aqueous sodium bicarbonate solution (824 kg). The -toluene solution was dried by , dis-tillation of -the -toluene/water azeotrope un-til the temperature of the solution reached 125 C. In an alternative procedure the ; 25 toluene was replaced by methyl isobutyl ketone ( 1850 kg).
(e) Benzoylation Benzoyl chloride ( 82 kg~ was added to the toluene solution over a period of 0. 25 hour and the mixture was heated under reflux for a further one hour. The mixture was diluted with toluene (1000 kg) and 3~3;~
:'' then s-tirred first with wa-ter (300 kg) at 60 C followed by 5%w aqueous sodium bicalibonate solution (915 kg) again a-t 60C. The toluene was then removed Erom -the solution under reduced pressure : ,.
i~ (40 mm Hg) and the residue was then stripped wi-th nitrogen at 140 C
:
and a pressure of 25 mm ~Ig. The analysis of the product (111ll kg) ~- obtained was:
"ester" 73.6%w "desbenzoyl ester" o.6%w ethyl benzoate 2.7%w remainder 23.1%w It will be seen tha-t the concentration of "ester" in -the product is more than double that in -the original star-tirlg material, and, moreover, the actual weight of "ester" present has been raised from 531 kg to 820 kg.
This product, optionally combined with crude product from the ~ es-ter synthesis, may be crystallized from 20-25%w me-thyl isobu-tyl ke-tone -~ in hexane (weight ratio solid: solvent = 1.5:1) -to give pure es-ter.
-E~A~LE II
The starting material was a mother liquor from -the crystalliza-tion of crude isopropyl ~-benzoyl-1'~-(3-chloro-~-fluorophenyl)-2-amino-.:
propionate irom me-thyl isobu-tyl ketone/hexane. This mo-ther liquor was concentrated -to give a residue containing 60%w of the ester and 2%w of the corresponding "desbenzoyl ester".
(a) Reaction with aq~ueous sodium hydroxide The residue (327 g) was s-tirred vigorously with a 10% aqueous solution of sodium bydroxide (437 g) for three hours at 90-95 C.
(b) Extrac-tion c The agueous mixture was then ex-tracted three times each with 300 g o~ -tetractlloroe-thylene at 60-70C.
'--1~63'~1;3Z
~' (c) Acidi~ication ____ The aqueous mixture was therl acidified with 95%w suLphuric acid (65 g) and extracted with tetrachloroethylene (2000 g). The tetrachloroethylene was removed ~rom the extract under reduced pressure (ll~0 C/100 mg llg). At this stage the residue contained ` 69.5%w "acid" and 7.2%w "desbenzoyl acid".
(d) Esteri~ication The residue (270 g) was mixed with isopropanol (95 g) and 95%w sulphuric acid (27 g~ and the mixture was heated under re~lux for o.5 hour. ~-ter this aqueous isopropanol was distilled of~` and simultaneously ~resh isopropanol was added at a rate equal to the distilla-tion rate. The to-tal reaction time was 5 to 6 hollrs a~ter which the excess isopropanol was removed under reduced pressure.
The residue was taken up in toluene and the organic phase was washed first with water (210 g~ and then 5%w sodium bicarbonate solution (210 g) at 50 C. The toluene solution was then dried by distillation o~ the toluene/water azeotrope.
(e) Benioylation Benzoyl chloride (25 g) was added to the toluene solution over a period o~ 0. 25 hour at 125 c, and the mixture was then stirred under re~l-ux ~or a further one hour. rrhe mix-ture was dilu-ted with toluene (250 ~ and then stirred with water (65 g) at 70C. The organic phase was then washed wi-th 5%w sodiuml bicarbona-te solution and the toluene was removed under reduced pressure. The residue was then stripped at 11~0 C with nitrogen under reduced pressure ( 25 mm Hg).
The residue (24O g) had -the ~ollowing composition:
, , _ 9 _ ' - - - .- ...... .
36~Z
:.' '"`
Isopropyl N-benzoyl-N-(3-chloro-4-fluorophenyl)-2-.. ~ aminopropionate 87.6%w "desbenzoyl ester" ~ 0.1%wisopropyl benzoate 2. 4~oWremainder 10%wThis crude "ester" could be readily recrystallized from a methyl isobutyl ketone/hexane mixture.
EXAMPLE III
The starting material was the same as that used i.n Example II
and steps (a), (b) and (c~ of the process were identical to those . of ExQ~ple II.
(d) Esteri~ication This step was carried out using 245 g of the residue ~rom step (c~, methanol (45 g) and 95%w sulphuric acid (25 g). The esterification conditions and work-up procedure were as described in Example II (d).
(e~ Benzoylation This step was carried out using -the procedure o:~ Example II(e).
The residue ob-tained (230 g) had the ~ollowing composition:
methyl N-benzoyl-N-(3-chloro-4-~luorophenyl)-2-aminopropionate 88.5%w methyl N-(3-chloro-4-~luorophenyl~-2-amino-propionate 0.2%w isopropyl N-benzoyl-N-(3-chloro-4-.~luorophenyl)-
2-aminopropionate 1. 0~7W
me-thyl benzoate 3.0lw remainder 7.3/w This crude es-ter could also be ~urther puri~iea by re-crystallization ~rom a methyl isobu-tyl ketone/hexane mixture.
_ 10 -
me-thyl benzoate 3.0lw remainder 7.3/w This crude es-ter could also be ~urther puri~iea by re-crystallization ~rom a methyl isobu-tyl ketone/hexane mixture.
_ 10 -
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Process for the recovery of an ester of the general formula (I) wherein X and Y each represents a fluorine or chlorine atom and R represents an alkyl group of 1 to 3 carbon atoms, from a mother liquor obtained after crystallization of the crude ester from an organic solvent medium, which comprises:
(a) treating the mother liquor or the residue therefrom with an aqueous alkali metal base to give an aqueous phase containing an alkali metal salt of the carboxylic acid derived from the saponified ester;
(b) contacting the aqueous phase with a substantially water-immis-cible organic solvent;
(c) acidifying the aqueous phase with a mineral acid;
(d) esterifying the liberated carboxylic acid(s) with an alkanol of 1 to 3 carbon atoms in the presence of an acid catalyst, and, optionally, (e) benzoylating the esterified product with a benzoyl halide under substantially anhydrous conditions.
(a) treating the mother liquor or the residue therefrom with an aqueous alkali metal base to give an aqueous phase containing an alkali metal salt of the carboxylic acid derived from the saponified ester;
(b) contacting the aqueous phase with a substantially water-immis-cible organic solvent;
(c) acidifying the aqueous phase with a mineral acid;
(d) esterifying the liberated carboxylic acid(s) with an alkanol of 1 to 3 carbon atoms in the presence of an acid catalyst, and, optionally, (e) benzoylating the esterified product with a benzoyl halide under substantially anhydrous conditions.
2. Process according to claim 1, wherein in the esters and acids present are converted in step (a) into water-soluble alkali metal salts by treatment with aqueous sodium hydroxide.
3. Process according to claim 1, wherein in the treatment step (a) a temperature from 50-100°C is applied.
4. Process according to claim 1, wherein the aqueous phase is contacted with a halogenated hydrocarbon, an ether or with a ketone optionally mixed with a hydrocarbon.
5. Process according to claim 4, wherein the aqueous phase is contacted with tetrachloroethylene.
6. Process according to claim 1, wherein the aqueous phase from step (b) is treated with a mineral acid at a temperature between 30-50°C.
7. Process according to claim 1, wherein the esterification of step (d) is carried out with an alkanol different from the one corresponding to the ester originally present in the mother liquor.
8. Process according to claim 7, wherein the residue of the esterification is diluted with toluene.
9. A process according to claim 1, wherein benzoylchloride is used as benzoylating agent.
10. A process according to claim 9, wherein benzoyl chloride is used in an 80-100% molar excess over the amount of "desbenzoyl ester" present.
11. A process according to claim 2 wherein the aqueous sodium hydroxide is a 5% to 20% by weight solution.
12. A process according to claim 6 wherein the mineral acid is sulphuric acid.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB660776A GB1571804A (en) | 1976-02-19 | 1976-02-19 | Recovery of esters derived from n-benzoyl-n-2-aminopropionic acids |
| GB6607/76 | 1976-02-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1106392A true CA1106392A (en) | 1981-08-04 |
Family
ID=9817556
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA270,792A Expired CA1106392A (en) | 1976-02-19 | 1977-02-01 | Recovery of herbicidal esters |
Country Status (11)
| Country | Link |
|---|---|
| JP (1) | JPS52100436A (en) |
| BE (1) | BE851460A (en) |
| BG (1) | BG27892A3 (en) |
| CA (1) | CA1106392A (en) |
| CH (1) | CH632235A5 (en) |
| DE (1) | DE2706823A1 (en) |
| FR (1) | FR2341561A1 (en) |
| GB (1) | GB1571804A (en) |
| IT (1) | IT1074674B (en) |
| NL (1) | NL7701670A (en) |
| SU (1) | SU644376A3 (en) |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1164160A (en) * | 1966-12-30 | 1969-09-17 | Shell Int Research | N,N-Disubstituted Amino Acid Derivatives and their use as Herbicides |
| GB1289283A (en) * | 1970-03-04 | 1972-09-13 |
-
1976
- 1976-02-19 GB GB660776A patent/GB1571804A/en not_active Expired
-
1977
- 1977-02-01 CA CA270,792A patent/CA1106392A/en not_active Expired
- 1977-02-16 BE BE1007950A patent/BE851460A/en not_active IP Right Cessation
- 1977-02-17 BG BG7735440A patent/BG27892A3/en unknown
- 1977-02-17 IT IT2040777A patent/IT1074674B/en active
- 1977-02-17 SU SU772453151A patent/SU644376A3/en active
- 1977-02-17 NL NL7701670A patent/NL7701670A/en not_active Application Discontinuation
- 1977-02-17 JP JP1560577A patent/JPS52100436A/en active Granted
- 1977-02-17 DE DE19772706823 patent/DE2706823A1/en active Granted
- 1977-02-17 CH CH199077A patent/CH632235A5/en not_active IP Right Cessation
- 1977-02-17 FR FR7704543A patent/FR2341561A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| FR2341561B1 (en) | 1980-10-10 |
| GB1571804A (en) | 1980-07-16 |
| BE851460A (en) | 1977-08-16 |
| FR2341561A1 (en) | 1977-09-16 |
| DE2706823A1 (en) | 1977-09-01 |
| DE2706823C2 (en) | 1989-01-05 |
| JPS6125021B2 (en) | 1986-06-13 |
| JPS52100436A (en) | 1977-08-23 |
| IT1074674B (en) | 1985-04-20 |
| CH632235A5 (en) | 1982-09-30 |
| NL7701670A (en) | 1977-08-23 |
| SU644376A3 (en) | 1979-01-25 |
| BG27892A3 (en) | 1980-01-15 |
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