Development of an Efficient Synthesis of (2-Aminopyrimidin-5-yl) Boronic Acid

A practical and cost-effective synthesis of (2-aminopyrimidin-5-yl) boronic acid 1b has been developed. Key features of the synthesis include the inexpensive in situ protection of the amine via bis-silylation using TMSCl followed by metal–halogen exchange using n-BuLi and trapping with B­(Oi-Pr)3. The water-soluble boronic acid is isolated by a well-designed acid–base sequence providing the target in 80% yield and high purity for the two-step process. The large-scale (15 kg) implementation of a Suzuki–Miyaura borylation to form the pinacol boronic ester is also described.