ES336595A3 - A procedure in liquid phase for the preparation of alkyl esters of benzymidazole - 2 - carbamic acids. (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

A liquid phase process for the preparation of alkyl esters of benzimidazole-2-carbamic acids of the formula: ** (See formula) ** where: X is selected from the group consisting of hydrogen, halogen, alkyl of less than 7 carbon atoms and alkoxy of less than 7 carbon atoms, And it is selected from the group consisting of hydrogen, chlorine, nitro, methyl and ethyl, R is selected from the group consisting of aliphatic hydrocarbons of less than 7 carbon atoms Y n is a positive integer less than 4; constituting said procedure the operations of (a) adding from 0.5 to 0.75 mole equivalents of dimethyl sulfate (based on thiourea) on a mixture formed by a ratio of thiourea to water comprised between 4: 1 and 1: 4, maintaining at temperatures reflux for the time necessary to complete the reaction and then add enough water to form an aqueous solution of the resulting mixture, (b) adding to said mixture 1 to 2 mole equivalents (based on thiourea) of lower alkyl chloroformate and 1.5 to 3 mole equivalents (based on thiourea) of a base selected from the group consisting of alkali metal and alkaline earth metal hydroxides, the addition of said base being carried out at a rate such that the pH of the resulting mixture is kept between 4 and 9, the temperature of the reaction mixture being maintained between -10º and + 50º C, (c) adding to the resulting mixture of 1 to 4 mole equivalents (based on thiourea) of an acid with an ionization constant ranging from 1 x 10-2 to 1 x 10-7 and from 0.5 to 2 equivalents in moles of o-phenylenediamine at respective rates of addition such that the pH of the resulting mixture is maintained between 4 and 8, keeping the temperature of the reaction mixture between about 30º C and 100º C and then stirring the resulting mixture at about 30-100º C. 100º C for about 10 hours to 30 minutes to complete the reaction, cool said mixture to about 0-40º C and filter out the desired product. (Machine-translation by Google Translate, not legally binding)