Continuous flow synthesis of heterocyclic scaffolds Design principles of multistep systems – A review
KLÁRA LÖVEI1,2*, PÉTER BANA3, RÓBERT ÖRKÉNYI3, GYÖRGY I. TÚRÓS1, JÁNOS ÉLES1, ZOLTÁN NOVÁK2, FERENC FAIGL3,4
*Corresponding author
1. Gedeon Richter Plc., Gyömroi út 19-21., Budapest, H 1103, Hungary
2. MTA-ELTE “Lendület” Catalysis and Organic Synthesis Research Group, Institute of Chemistry, Eötvös University, Pázmány Péter stny. 1/a., Budapest, H 1117, Hungary
3. Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, Budafoki út 8., Budapest, H-1111, Hungary
4. MTA-BME Organic Chemical Technology Research Group, Budafoki út 8., Budapest, H 1111, Hungary
Abstract
The synthesis of novel heterocycles is an essential task in small-molecule drug discovery. Continuous flow processing opens the way for a new paradigm in laboratory-scale synthesis as well as pharmaceutical manufacturing. Based on our experiences with the multistep synthesis of condensed benzothiazoles, we gathered some of the key design features in light of literature examples.
INTRODUCTION
The design and preparation of new heterocycles as scaffolds or building blocks for active pharmaceutical ingredients (APIs) is a challenging area in today’s small-molecule drug discovery. Chemists seek new approaches and technologies that can be applied to produce novel structures, while keeping an eye on the improvement of the efficiency and productivity of the chemical processes. The new “enabling technologies” (1, 2), like flow chemistry (3, 4), provide practical solutions for the synthesis of heterocyclic compounds. The emerging trends and recent synthetic results indicate the growing importance of continuous flow manufacturing in academia as well as in pharmaceutical industry (5–9). These efforts are also pointing towards the realization of continuous technologies for API synthesis (10, 11) in accordance with FDA’s recommendations (12, 13).
However, the application of flow methods demands a paradigm shift in synthetic mentality and a new knowledge base, which can mean a barrier for those, who are unfamiliar with it. Our experience during the introduction of this technology to laboratory practice inspired us to compile ...
