| In recent years, 18F labeled ligands have played a key role in positron emission tomography (PET) imaging. Due to the short half-life of these radiolabeled compounds, microwave and continuous flow microreactor techniques have proven extremely useful by accelerating reactions in under ten minutes with high purity. With the production of radiotracers and radiopharmaceuticals relying on automated synthesis platforms for production, multi-step reactions performed in a continuous flow process are of great significance. When developing central nervous system (CNS) imaging agents, optimizing lipophilicity of the drug to maximize blood brain barrier penetration is vital, and typically, the addition of even one methylene spacer or a change in hybridization can have an extreme impact on the drug's properties. Palladium catalyzed Sonogashira couplings of &ohgr;-alkynyl tosylates, particularly propargyl tosylates, with aryl halides have being developed in a continuous flow process under copper, ligand, and amine-free conditions. Homologs of CNS imaging agents nifrolidine and fallypride are being investigated as well as additional analogues involving the rapid hydrogenation products under microwave conditions. |
