Process Safety Evaluation and Scale-up of a Lactam Reduction with NaBH₄ and TFA

The development of a practical and scalable method for the synthesis of morpholine derivative <b>2</b> via reduction of lactam <b>1</b> using NaBH₄ and trifluoroacetic acid (TFA) is described. Through the mechanistic studies using ¹¹B NMR spectroscopy, we observed that active species were generated during TFA addition, which avoids the deactivation of the active species involved in the reduction process. Process safety assessments were performed on the basis of the reaction mechanism using reaction calorimetry and gas evolution analyses. Furthermore, safety equipment was prepared to prevent the leakage of diborane gas during the reaction, and the process was successfully scaled up to the pilot plant at a 35 kg scale