Synthesis, crystal and molecular structure of methyl[(4-acetamidophenyl)sulfonyl]carbamate, precursor of herbicide Asulam

Abstract

The methyl[(4-aminophenyl)sulfonyl]carbamate is commercially known as Asulam. It is the most common trade name for a systemic and synergistic herbicide, which is incorporated by the plants through their foliage and roots, and is extensively used against weeds and brackens in the cultivation of gramineous, citric, banana and sugarcane, among others. The industrial procedure for obtaining this carbamic compound includes the base-catalyzed hydrolysis of the methyl[(4-acetamidophenyl)sulfonyl]carbamate. In this work a simple and conventional method for the synthesis of the Asulam intermediate and the characterization of its crystal and molecular structure utilizing X-Ray Diffraction and IR, NMR 1H and 13C spectroscopic techniques is presented. The synthetic precursor will be used as substrate of the hydrolytic enzyme in the development of a new biocatalytic preparation of the herbicide Asulam. Therefore, the knowledge of its structure will help not only to define the physical characteristics of its more stable conformation, but also will allow predicting the compatibility between the possible enzymes to be used and the substrate, according to the properties of their catalytic centers. The title compound was synthesized from 4-acetamidophenylsulfonamide and methylchloroformate in the presence of anhydrous K2CO3 and acetone, extracted with ethyl ether and recrystallized from methanol. The studied compound was obtained as crystalline solid in 62% yield. The crystals of intermediate were grown by slow evaporation from methanol solution. They are monoclinic, space group P21/n; a = 8.681(4), b = 8.174(3), c = 17.583(3) Å, ß= 92.40(1) º, Z = 4. The molecular packing shows a bidimensional hydrogen bond network.