How does dichloromethane's reactivity affect its use in pharmaceutical synthesis?

Dichloromethane is widely used in pharmaceutical manufacturing as a reaction and extraction solvent, prized for its high solvency, low boiling point, and clean evaporation. However, its chemical reactivity is often underestimated. Bridged amines like quinine and strychnine react readily with DCM, as do tertiary and secondary amines, forming aminal salts. Pyridine reacts twice as fast on the second substitution, and DMAP is seven times more reactive than pyridine. Even common reagents like HOBt and thiols can react under phase-transfer conditions. Grignard reagents in the presence of iron salts also attack DCM. This means process chemists must screen for DCM adducts, especially when handling amine-containing intermediates. The low boiling point also complicates storage and VOC compliance, making it less attractive for scale-up despite its efficiency. Producers of pharmaceutical-grade DCM, such as those with CDE filings in China, emphasize purity and traceability, but reactivity remains a hidden variable in process development.