Methods for the synthesis of pharmaceuticals have improved over the years, however, the technology and tools used to perform synthetic operations have remained the same. Batch-mode processes are still common but many improvements can be made by using modern technologies. Recently, the use of machine-assisted protocols has increased, with flow-based chemical synthesis being extensively investigated. Under dynamic flow regimes, mixing and heat transfer can be more accurately controlled, the use of solid-phase reagents and catalysts can facilitate purification, and tedious downstream processes (workup, extraction, and purification) are reduced.

Steven V. Ley and co-workers, University of Cambridge, UK, have been evaluating the utility of flow-based syntheses to accelerate multistep routes to highly complex, medically relevant compounds, in this case Meclinertant (SR48692, pictured). They show that new technologies can help to overcome many synthetic issues of the existing batch process. In this case, flow chemistry has allowed control of exothermic events, controlled the superheating of solvents, and streamlined the synthesis by allowing reaction telescoping. It has also helped to prevent back mixing and the accumulation of byproducts. The use of polymer-supported reagents has simplified downstream processing and enhanced the safety of reactions, and in-line monitoring can track hazardous intermediates.

These new technologies have been shown to be powerful synthetic tools, although care must be taken not to convert them to expensive solutions to nonexistent problems.

• A Machine-Assisted Flow Synthesis of SR48692: A Probe for the Investigation of Neurotensin Receptor-1,
  Claudio Battilocchio, Benjamin J. Deadman, Nikzad Nikbin, Matthew O. Kitching, Ian R. Baxendale, Steven V. Ley,
  Chem. Eur. J. 2013.
  DOI: 10.1002/chem.201300696