In 2005, the American Chemical Society (ACS) Green Chemistry Institute (GCI) and global pharmaceutical companies established the ACS GCI Pharmaceutical Roundtable to encourage the integration of green chemistry and engineering into the pharmaceutical industry. The Roundtable developed a list of key research areas in green chemistry in 2007, which has served as a guide for focusing green chemistry research. Following that publication, the Roundtable companies have identified a list of the key green engineering research areas that is intended to be the required companion of the first list. This publication summarizes the process used to identify and agree on the top key green engineering research areas and describes these areas, highlighting their research challenges and opportunities for improvements from the perspective of the pharmaceutical industry.
The
American Chemical Society (ACS) Green Chemistry Institute (GCI)
Pharmaceutical Roundtable conducted a study to elucidate the value
of continuous processing, which had been defined as a key research
area for green engineering. In the course of defining the business
case for continuous processing, individual cases were collected and
evaluated to determine specific drivers to implement continuous processing
and to find key success factors. The magnitude and timing of effects
and the relation to the principles of green chemistry were investigated.
Continuous manufacturing as a way of producing fine chemicals, active pharmaceutical ingredients, and finished dosage forms is gaining widespread attention. Although potential benefits over traditional batch-wise production have been discussed at many occasions and appear evident, continuous processes are only slowly being implemented.
The development of a continuous diazomethane generator comprising a continuous stirred tank reactor (CSTR) cascade and membrane separation technology is reported. This reactor concept was applied for the telescoped three-step synthesis of a chiral α-chloroketone, a key building block for many HIV protease inhibitors, via a modified Arndt−Eistert reaction starting from N-protected L-phenylalanine. The initial mixed anhydride was generated in a coil reactor and directly introduced into the CSTR diazomethane cascade. The use of a semipermeable Teflon membrane (AF-2400) allowed the generation of anhydrous diazomethane, which diffuses through the membrane into the CSTR where it is immediately consumed by the anhydride to furnish the corresponding diazoketone. The subsequent halogenation with concentrated HCl was performed downstream in batch and allowed production of the α-chloroketone on a multigram scale, with a productivity of 1.54 g/h (5.2 mmol/h).
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