Method for controlling the growth of weeds in a field containing growing plants of cotton

#The invention relates to selective herbicides and particularly to alkyl N-3-carbamoyloxyphenyl-carbamates and a method of using the same.

#The known herbicides which are alkyl N-3-carbamoyloxyphenylcarbamates are effective in controlling weeds in crops of sugar beets and other economically less important crops, but they damage cotton plants severely when employed in amounts effective to destroy the weeds.

#The object of this invention is the provision of herbicides which can be used to advantage in cotton crops to control weeds without damaging the crop plants.

#The following Examples illustrate the preparation of compounds of this invention and their use.

#A solution of 14.6 g 3-N-carbethoxyamino-phenyl chloroformic acid ester in 30 ml ethyl acetate and a solution of 8.3 g potassium carbonate in 30 ml water were added dropwise and simultaneously with stirring to a mixture of 5.3 g N-ethylisopropylamine, 50 ml water, and 30 ml ethyl acetate at 10.degree. to 15.degree. C. Stirring was continued 30 minutes while the reaction mixture was cooled with ice. The organic phase was separated from the aqueous phase, washed at 0.degree. C with a little dilute sodium hydroxide solution and with water, dried with desiccated magnesium sulfate, and partly evaporated in a vacuum. The residue was mixed with pentane and cooled with ice, whereby 14.1 g ethyl N-3-(N-ethyl-N-isopropylcarbamoyloxy)-phenyl-carbamate was precipitated in crystalline form (80% yield). The compound will be referred to hereinafter as Compound No. 1. It melts at 65.degree. to 66.degree. C.

#A solution of 16.7 g 3-hydroxycarbanilic acid methyl ester and 19.6 g N,N-dipropylcarbamoyl chloride in about 50 ml anhydrous pyridine was heated 45 minutes at 90.degree. C in a water bath. The solvent was evaporated in a vacuum, the residue was dissolved in ethyl acetate, and the solution was washed with a little dilute sodium hydroxide solution, with dilute hydrochloric acid, and with water at 0.degree. C, dried with magnesium sulfate, and evaporated in a vacuum. When pentane was added to the residue, ethyl N-3-(N,N-dipropylcarbamoyloxy)-phenyl-carbamate (Compound 2) crystallized. When recrystallized from tetrahydrofurane and pentane, it melted at 82.degree. - 84.degree. C. The yield was 21.0 g (68%).