Development of a Scalable Route toward an Alkylated 1,2,4-Triazol, a Key Starting Material for CXCR3 Antagonist ACT-777991

Several synthetic routes toward triazole building block 2-(3-methyl-1H-1,2,4-triazol-1-yl)acetic acid are described. The main problems of the initial synthetic route via alkylation of 3-Me-1H-1,2,4-triazole, such as poor regioselectivity, low yield, and purification by column chromatography, could be significantly improved or completely avoided in the second-generation approaches. Key concepts for the design of the alternative synthesis approaches to solve the problem of regioselectivity were the desymmetrization of 3,5-dibromo-1H-1,2,4-triazole and the de novo synthesis of the triazole core. The scalability of all routes was demonstrated on >100 g scale.