Sulfone Displacement Approach for Large-Scale Synthesis of 4-Chloro-N-(1-methyl-1H-pyrazol-4-yl)pyrimidin-2-amine

Route evaluation, process development, and large-scale manufacturing of 4-chloro-N-(1-methyl-1H-pyrazol-4-yl)pyrimidin-2-amine (1) are described. The improved route consists of two linear chemical steps: oxidation of 4-chloro-2-(methylthio)pyrimidine (11) to 4-chloro-2-(methylsulfonyl)pyrimidine (7) and displacement of the sulfonyl with N-(1-methyl-1H-pyrazol-4-yl)formamide (10) under basic conditions followed by in situ hydrolysis of the N-formyl intermediate to deliver compound 1. N-(1-Methyl-1H-pyrazol-4-yl)formamide (10) was readily prepared from 1-methyl-1H-pyrazol-4-amine (4) via reaction with formic acid. The route allows for large-scale production of 4-chloro-N-(1-methyl-1H-pyrazol-4-yl)pyrimidin-2-amine (1). Density functional theory (DFT) calculations were carried out to better understand the observed reactivity and selectivity.