CA1064048A - Process for the preparation of n-carbamoyloxy-phenyl-carbamates - Google Patents

Abstract

ABSTRACT

This invention relates to a novel process for the preparation of compounds of the formula I

(I) (wherein R1 stands for alkyl, cycloalkyl or optionally halogeno- or Alkyl-substituted aryl; R2 is hydrogen or alkyl; R3 is alkyl) which comprises reacting a carbamate of the formula III, (III) (wherein R3 has the same meaning as stated above) with an ester of the formula II, (II) (wherein R1 and R2 are as stated above and A stands for a phenyl group bearing at least two electron-attracting substituents) in the presence of a base.
The compounds mentioned are useful as herbidides.

Description

This invention relates to the preparation of N-(Carbamoyl-oxy-phenyl)-carbamates, which are useful as herbicidal agents.
According to the present invention, there is provided a process for the preparation of compounds of the formula 1, O-C-N
\ R2 NH-~C - OR
~ ~ O
(wherein Rl stands for alkyl, cycloalkyl or optionally halogeno- or alkyl-substituted aryl;
R2 is Hydrogen or alkyl;
R is alkyl) which comprises reacting a carbama~e of the fol~ula III, OH

- NH - C - OR (III) , ..

(wherein R has the same meanings as stated above) with an ester of the formula Il, IR
; 11 ~
AO - C - N ~II) ~wherein Rl and R2 are as stated above and A stands for a phenyl group bear-ing at laast two electrone-attracting substituen~s) in the presence of a ~il base.
The term "alkyl" relates to straight or branched chained satured 2Q aliphatic hydrocarbon groups having 1-7 carbon atoms (e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, etc.) The cycloalkyl groups contain 3-7 car-bon atoms ~e.g. cyclopropyl cyclopentyl, cyclohexyl, e~c.) The optionally -1 ~

.

halogeno-substituted or alkyl-substituted aryl group may be preferably a phenyl,monochlorophenyl, monobromophenyl, or methylphenyl gro~lp, preferably a m-tolyl or phenyl group).
Symbol A represents preferably a phenyl group, substi-tuted by at least two halog~n atoms, preferably chlorine atoms. As a suitable value for A there may be mentioned the pentachlorophenyl group.
The process of the present invention is par~icularly suitable for the preparation of the following compounds of the formula I: methyl-N-3-[N'-(3'~methyl-phenyl)-carbamoyl] -phenyl-carbamate; ethyl-N 3-~N'-~phenyl~-car-bamoyl]-phenyl-carbamate.
Carbamates of the formula I may be prepared by various methods.
A common feature o the said known procedures is the acylation of the acidic hydroxyl group of the corresponding N-hydroxy-phenyl-carbamate by using reactive carbonic acid derivatives.
When using isocyanate the compounds of the formula I may be prepared in a one-step additional reac~ion in the presence of a basic catalyst ~J. Org.
Chem. 28~ 658 (1963); Helv. Chim. Acta 48J 2005 (1965); Hungarian Patent No.
_ , 154~047 ~
The end-products of the formula I may also prepared in a substi-tution reaction - phosgenation - in two steps, whereby at first the correspond-ing chloro-fonnate is formed and thereafter reacted with the corresponding ; amine, or the carbamic acid chloride previously formed from the amine is sub-sequently reacted with the corresponding N-hydroxy-phenyl-carbamate ~Meth.
der Org. Chem. 8, 101 ~1952); Chem. Pharm~ Bull. 15~ 2015 ~1967);
Hungarian Patents Nos. 154~047 and 157~04~o The compounds of the formula I may also be prepared by substitution reaction without previous preparation o the chloroformate or the carbamic acid chloride by means of simultaneous reaction of phosgen, the correspond-ing N-hydroxy-phenyl-carbamate and the corresponding amine ~Hungarian Pa~ent 3Q No. 154~ Q~4) ~
l~e use of so-called active carbamic acid esters as acyla~ing agent is known ~rom peptide chemistry French Patent No. 872~920; Nature 115, ~85 .

(1955).
It is knowrl furtheron that highly reactive carbamic acid phenyl-esters may be used for N-acylation ~Hungarian Patent No. 162,382).
According to the process of the present invention ac~ive M-aryl-car-bamic acid esters are used for the ~-acylation of phenol derivative bearing primary substituted groups as substituents.
On studying acylation reactions of N-hydroxyphenyl-carbamates it has been found that compounds of the formula I may be prepared with the acid of a chemically novel process in uniform and highly pure form by using active carbamic acid phenyl esters. This process is more advantageous both from the quanti~ative and qualitative point of view than the acylation carried out with phosgen, iSQCyanateS or active N-alkyl-carbamoyl-esters. Thus while according to known methods O-carbamoylation of N-hydroxy-phenyl-carbamates was carried out with the - aid of an addition reaction (isocyanate) or a two-step substitution reaction (phosgene~ the present invention provides a single-step substi~ution reaction for the realisation of O-carbamoyla~ion.
The reaction may be preferably carried out in an organic solvent in the presence of a base. For this purpose inorganic bases or tertiary amines, preferably trialkylamines (e.g. triethylamine) or pyridine may be used.
The reaction may be preferably accomplished in an organic solvent.
It is preferred ~o use an organic solvent in which two of the starting materials (the base is included too) are soluble and the compound formed is either in-soluble or may be isolated by precipitation or fractional crystallisa~ion in pure form, while the impu~ities remain in the solution. One may preferably use aromatic hydrocarbons (e.g. toluene), lower ketones ~e.g. acetsne), esters Ce.g. ethylacetate~ ethers Ce.g. dioxane)~ chlorinated hydrocarbones ~e.g.
chloroform). ~hen using an inorganic base the reac~ion product may be puri-fied - if necessary - by suspending in water.
The carba~ylating agents of the formula II may be prepared by known methods used for the preparation of phenyl or ~hiophenylesters ~J. Org. Chem.
28, 658 ~19~3)] .
The sal~ of the phenol component of the active ester formed in the reaction may be readily separated from the reaction mixture and re-introduced into the process, thus it may be used for the prepa:ration of thc active ester, e.g. as follows:
The mother-lye is stirred with an excess of 10% (related to the phenol component) of a 10% sodium hydroxide solution. After separation of the two phases the aqueous layer is acidified wi~h l:l diluted hydrochloric acid to the pH value of 1, the precipitated phenol is filtered, washed and dried.
Degree of recovery 90%.
The ter~iary amine may be recovered as hydrochloric acid salt by evaporation or after alkalisation by means of di~*illation. The simple and economic recovery method in addition to with the purity of the product and the high yields render the process very economic.
The compounds of the formula I prepared according to the process of the present invention may be conver~ed into herbicidal compositions by methods kno~n per ~se. The active ingredient is preferably formulated as a powder mixture or stabilised emulsion. The emulsions may be prepared by admixing the active ingredient with a suitable solven~ and, if desired, with one or more enulsifying agents. The amount of ~he additive and the solventl ~ -the type and character of the additive and the carrier and the percentage 2Q amount of the active ingredient are selected under taking into c~nsideration the given circumstances and requirements of application. The usual carriers and additives are applied by using formulating methods known ~or the preparation of pesticides. The active ingredient content may vary between wide ranges and may be generally from about 0,001% to about 95%.
F`urther details of the present invention may be found in the examples, without limiting the scope of the claims to the examples.
.
To 50 ml of chloroform 8,0g ~0,02 moles) of pentachlorophenyl N-Cm-tolyl)-carbamate and 3,34g (0,02 moles) o methyl-N-(3-hydroxyphenyl)-50 carbamate are add~d. At 25C 2,1g (0,0205 moles) of triethylamine are added and the reaction mixture is stirred at 25C for 5 hours. The precipitated product is filtered, washed with chloroform and dried. Thus 4,8g methyl-N-3-[N'-~3'-methyl-phenyl)-carbamoyl]~phellyl-carbamate are obtained. Mp.:
1~6-14SC.
Example 2 The process according to example 1 is carried out except that as reaction medium 50 ml of chloro-benzene are used ancl the precipita~ed reaction product is washed with chloro-benzene. Yield ~,8 g, mp.: 1~6-1~8C.
Example 3 The process according to example 1 is carried out except that as reaction medium 50 ml of ethyl acetate is used. After stirring the reaction mixture at 25C for 5 hours, the solution is evaporated, the residue is suspended in toluene, the product is filtered off, washed with water and dried. Yield 5,0 g, m.p.: 1~6-1~8C.
Example 4 15~43 g (OJO4 moles) of pentachlorophenyl-N-phenyl-carbamate and 7,24 g (0,0~ moles~ of e-thyl-N-~3-hydroxyphenyl)-carbamate are added to 100 ml of ethyl acetate~ After addition of ~.2 g ~0,00~1 moles) oE triethy-lamine the reaction mixture is stirred at 25C for 5 hours. The solvent is distilled off and the residual oil is dissolved in 100 ml of warm benzene. Gn cooling the precipitated crystals are filtered off, washed with benzene and dried. Thus 11 g of ethyl-N-[3-~N'-phenyl)-carbamoyl]-phenyl-carbamate are obtainecl. Yield 91,8%, Mp.:
The starting material may be prepared as follows:
To a mixture of 27 g ~0,1 mole~ of pentachlorophenol, 13,1 g ~011l moles) of phenyl-isocyanate and 100 ml of toluene, 0,8 ml of triethylamine are added at 25C. The reaction mixture is stirred under cooling with ice-water for 3 hours ak 25C, whereupon the precipitated product is filtered off, washed and dried. Thus 35,1 g of pentachloro-phenyl-N-phenyl-carbamate are obtained. Yield: 90,5%.

Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Process for the preparation of compounds of the formula I, (I) (wherein R1 stands for alkyl, cycloalky or optionally halogeno- or alkyl-sub-stituted aryl;
R2 is hydrogen or alkyl;
R3 is alkyl) which comprises reacting a carbamate of the formula III, (III) (wherein R3 has the same meaning as stated above) with an ester of the formula II, (II) (wherein R1 and R2 are as stated above and A stands for a phenyl group bearing at least two electrone-attracting substituents) in the presence of a base.

2. Process according to claim 1, which comprises using a compound of the formula II pentachlorophenyl-N-(m-tolyl)-carbamate or pentachlorophenyl-N-phenyl-carbamate.

3. Process according to claim 1, which comprises using as starting material of the formula II methyl-N-(3-hydroxyphenyl)-carbamate or ethyl-N-(3-hydroxyphenyl)-carbamate.

4. Process according to any of claims 1-3, which comprises carrying out the reaction in the presence of a trialkylamine.

5. Process according to any of claims 1-3, which comprises carrying out the reaction in the presence of triethylamine.