Process Intensification and Increased Safety for the On-Demand Continuous Flow Synthesis of Dithiothreitol, a Crucial Component in Polymerase Chain Reaction Testing Kits

The importance of rapid access to diagnostics tools in the identification of pathogens─including their crucial component, bioreagents─was recently underscored in the COVID-19 pandemic. The currently adopted synthesis of dithiothreitol (DTT) involves four steps in batch with long reaction times and which generates a highly carcinogenic and mutagenic bis-epoxide intermediate. In this work, we have developed an intensified telescoped three-step continuous flow synthesis of DTT involving a base-mediated ring closure epoxidation, a nucleophilic epoxide opening with thioacetic acid, and an acid-mediated deacetylation. One of the key features is that the first two steps are conducted in a telescoped continuous flow fashion, allowing generation and consumption of the hazardous intermediate in situ, suppressing the need for its isolation, and improving the overall safety of the synthesis. The process is completed by an acid-catalyzed deacetylation and a subsequent recrystallization to afford the desired DTT. Flow chemistry allows here to intensify the process by using high temperatures and high pressures while minimizing the number of unit operations and improving the overall safety of the process. Our protocol permits the on-demand production of DTT in case of future outbreaks.