The Process Development of RG 12525 (2-{[4-(Tetrazol-5-ylmethylphenyl)-methoxy]phenoxymethyl}quinoline)

This contribution describes process improvements to provide a practical and cost-effective synthesis for the manufacture of RG 12525 which resulted in a 3-fold increase in overall yield. Improved solvent systems for chlorination and azidation reactions are described. Adjustments to the tetrazole-forming step eliminated azide sublimation and minimised this risk on scale-up. A robust solvent system was found to control the polymorphic form during crystallisation, which had hitherto been difficult due to the near-equivalence of melting points (154 and 157 °C) of the two known forms.