PROCESS FOR PREPARING 2-(5-BROMO-4-(1-CYCLOPROPYLNAPHTHALEN-4-YL)-4H-1,2,4-TRIAZOL-3-YLTHIO)ACETIC ACID

The object of the invention is a novel and efficient production method of 2-(5-bromo-4-(1-cyclopropylnaphthalen-4-yl)-4 H -1,2,4-triazol-3-ylthio)acetic acid of formula 1 known under the generic name lesinurad. The novel method is based on bromination of 2-(4-(1-cyclopropylnaphthalen-4-yl)-4 H -1,2,4-triazol-3-ylthio)acetic acid of formula 17, whose carboxyl function is protected by a trialkylsilyl group. When the novel method is used, the bromination reaction runs selectively and with a high conversion rate of the input compound. The introduction and deprotection of the used protecting group run very easily, so there is no need to isolate the produced intermediates of formula 18 and 19, which reduces the number of handling steps. The isolation of the product from the reaction mixture is advantageously based on the good crystallizing properties of the newly found salts of lesinurad of formula 21 and 22.